Influence Of Bentonite And Blast Furnace Slag To The Self Healing Behaviour Of Cracked Cement Paste - ITS Repository
FINAL PROJECT (RC14-1501)
INFLUENCE OF BENTONITE AND BLAST FURNACESLAG TO THE SELF HEALING BEHAVIOUR OF CRACKED CEMENT PASTE M. SAMSUL ANAM NRP. 31 11 100 076 Supervisor : Dr.Eng. Januarti Jaya Ekaputri, ST. MT. Prof. Dr. Ir. Triwulan, DEA. CIVIL ENGINEERING DEPARTMENT Faculty of Civil Engineering and Planning Institut Teknologi Sepuluh Nopember Surabaya 2016
TITLE PAGE FINAL PROJECT (RC14-1501)
INFLUENCE OF BENTONITE AND BLAST FURNACESLAG TO THE SELF HEALING BEHAVIOUR OF CRACKED CEMENT PASTE M. SAMSUL ANAM NRP. 31 11 100 076 Supervisor : Dr.Eng. Januarti Jaya Ekaputri, ST. MT. Prof. Dr. Ir. Triwulan, DEA.
APPROVAL SHEETCIVIL ENGINEERING DEPARTMENT Faculty of Civil Engineering and Planning Institut Teknologi Sepuluh Nopember Surabaya 2016
INFLUENCE OF BENTONITE AND BLAST FURNACE SLAG
TO THE SELF HEALING BEHAVIOUR OF CRACKED
CEMENT PASTEStudent Name : M. Samsul Anam NRP : 31 11 100 076
Departement : Civil Engineering Department FTSP – ITSSupervisor : Dr. Eng. Januarti J. E., ST. MT.
Prof. Dr. Ir. Triwulan, DEA. ABSTRACT
Cracks, caused by shrinkage and external loading faciliates the
ingress of aggressive and harmful substance into concrete and
reduce the durability of the structures. It is well known that self –
healing of cracks can significantly improve the durability of the
concrete structure. In this reseach, self healing propertis of the
cement paste containing bentonite and blast furnace slag were
studied. The self healing properties were evaluated by using 4index
parameters, including surface crack width (β ), crack depth
(α index ), tensile strength recovery, and flexural stiffness recovery.
In combination with microscopic obervation, a healing process
over time was drawn. The result show that bentonite can improve
healing properties, in term of surface crack width and crack
depth. In the other hand BFS also could also improve self healing
properties, in terms of crack depth, direst tensile regain, and
flexural stiffnes. Carbonation reaction still to be main mechanism
which contribute self healing process, althought continuedhydration still occure.
Keyword : cracks, self-healing, durability, bentonite, blast furnace slag
Thank to Almighty God who has given His favor to the author for finishing the research and completing the final project report entitled ""Influence of bentonite and blast furnace slag to the self-healing behavior in cracked cement paste". This research describe a solution to improve durability of the concrete structures which is due to a cracks in the concrete materials, by applying self-healing concrete approach. Since the durability is very important factor which is related to the age of buildings, the self-healing concrete is very important to develope. This reasearch focus on the influence of bentonite and blast furnace slag to the self-healing behaviour which is evaluated by using 6 parameters, i.e crack width, crack depth, tensile strength recovery, flexural stiffness recovery, pH, mineral closing crack, and cloride ion penetration to analyze the durability of the cracked cement paste. That 6 parameters are discused, both influence of each material and relationship between each parameter to the self-healing behaviour.
This research has been done for 8 months, which is started from March 2015 and fisnished on January 2016. Several testing, measurement, analysis and observation have been conducted in Laboratory of Concrete and Buiding Materials ITS, Cement Reseacrh Center PT. Semen Indonesia, Laboratory of Analysis and Instrumentation (Lab. TAKI) ITS, and Laboratory of Enviroment Quality ITS. Furthermore, the author likewise wish to express his profound and earnest appreciation for the individuals who have supported, guided and helped in finishing this research report, i.e :
1. The author’s beloved Parents, Supriyadi and Partutik. The author would like to thanks so much for their prayer, support, affection, advices, guidance, and help in all my life, their love is beyond any words.
2. Dr. Eng Januarti Jaya Ekaputri, ST., MT as first supervisor for his valuable guidance, encouragement, patient, correlation, advice, and suggestion which are very helpful in finishing this report. The author would like to thanks for for her time to share her great knowledge and great experiences to the author.
3. Prof. Dr. Ir. Triwulan, DEA as second supervisor, who has guided me with his worthy, valuable guidance, encouragement, patient, correlation, advice, suggestion and correction to improve the quality of this report. The author would like to thanks for for her time to share her great knowledge and great experiences to the author
4. Trieddy Susanto, ST, MT as external supervisor from PT.
Semen Indonesia. The author would like to thanks for his guidance, advice, suggestion, and correction to improve the quality of this report.
5. Mr. Basar, Mr. Hardjo, Mr. Totok, Mr. Supri, Mr. Ji as laboran in Laboratory of Concrete and Buidling Materials for their support and favor in conducting some testing and measurement of this reaseach.
6. The author’s Lab-mate, i.e Wawan, Alex, Novema, Luthfi Anas, James, Nizar, Ziad, Adi, Achsan, Henry, Kefi, Ila, Ruceh, Annisa, Inne, Like, Kiky, and Wuri, who have given beatiful and unforgettable memories as long as the author
conducted his research in the Laboratory of Concrete and Building Materials.
7. All lecturers of Civil Engineering Department ITS, who have transferred much knowledge to the author which very helpful in finishing final project report.
The author would like to thanks for guidance, instruction and help during
study at the Civil Engineering Departement
8. The author’s beloved friends in Civil Engineering Department’11 and S54. The author would like to thanks for togetherness and attention as long as the author study in Civil Engineering Departement ITS.
Big Familiy of Civil Engineering Department ITS 9.
Minister of Research and Higher Education which has fund the 10. Financial support for this research work.
11. PT. PT. Semen Indonesia for supporting cement materials, blast furnace slag, and supporting some experimen.
12. PT. Surya Beton Indonesia and PT. Varia Usaha Beton for supporting cement materials.
The last, this final project report is far from being perfect, but it is expected that this report will be useful not only for the researcher, but also the readers. For this reason, constructive thought full suggestions and critics are well come to make this report better.
. Surabaya, January 25, 2016
Author M. Samsul Anam 31 11 100076
TABLE OF CONTENTS
TITLE PAGE ................................................................................. i APPROVAL SHEET ..................................................................... i ABSTRACT .................................................................................. v PREFACE ...................................................................................vii TABLE OF CONTENT ............................................................... xi LIST OF FIGURE....................................................................... xv LIST OF TABLE ....................................................................... xxi
CHAPTER I INTRODUCTION .................................................. 1
1.1. Background ...................................................................... 1
1.2. Research Problems ........................................................... 4
1.3. Research Boundaries ........................................................ 5
1.4. Research Objective........................................................... 5
1.5. Benefits ............................................................................ 6
CHAPTER II LITERATURE REVIEW ...................................... 7
2.1. Crack on the Concrete Structures ..................................... 7
2.2. Conditions for Self-Healing ............................................. 8
2.3. Self-Healing Mechanism .................................................. 9
2.4. Self-Healing Mechanism with Continued Hydration ..... 11
2.5. The influence of Pozzoland to Ca(OH)
2 content ........... 13
2.6. Characteristics of Bentonite Clay ................................... 14
2.7. Chemical Structure of Montmorolinite .......................... 16
2.8. Autogenous Healing Concrete using Geomaterial ......... 18
2.9. Blast Furnace Slag as Autogenous Healing material ..... 23
CHAPTER III RESEARCH METHODOLOGY ....................... 35
3.1. Literature Riview ........................................................... 36
3.2. Preparation of Materials ................................................. 37
3.3. Analisys of Raw Materials Properties ............................ 37
3.3.1. Method to Determine Specific Gravity ..................... 37
3.3.2. Method to Determine Density ................................... 39
3.3.3. Method to determine SAI .......................................... 41
3.3.4. Flow Table Test ........................................................ 44
3.3.5. Particles Size Analyze .............................................. 45
3.3.6. X-Ray Fluoroscene ................................................... 46
3.3.7. X-Ray Diffraction ..................................................... 46
3.4. Mix Proportion Series .................................................... 47
3.5. Specimens Series ........................................................... 47
3.5.1. Dogbone/Briquet Specimen...................................... 48
3.5.2. Beam 10 x 10 x 40 .................................................... 48
3.6. Specimens Casting ......................................................... 51
3.7. Curing Condition ........................................................... 52
3.8. Introducing Artificial Crack .......................................... 53
3.9. Water Imersion Curing .................................................. 54
3.10. Self Healing Evaluation ................................................. 54
3.10.1. Ultrasonic Pulse Velocity Testing ......................... 54
3.10.2. Microscopic Investigation ...................................... 57
3.10.3. Four Point Bending Test ........................................ 62
5.10.4. Direct Tensile Strenght Test .................................. 63
5.10.5. Measuring pH of Specimens .................................. 65
5.10.6. Cloride Ion Penetration Test .................................. 67
5.10.7. XRD Analysis ........................................................ 69
CHAPTER IV RESULTS AND DISCUSSIONS ...................... 71
4.1. General Introduction ...................................................... 71
4.2. Testing Result of The Raw Materials ............................ 71
4.2.1. Spesific Gravity of Material ..................................... 71
4.2.2. Density of Material ................................................... 73
4.2.3. Strenght Activity Index ............................................ 75
4.2.4. XRD ......................................................................... 78
4.2.5. XRF .......................................................................... 82
4.2.6. Particles Size Distribution ........................................ 84
4.2.7. Spesific Surface Area (SSA) .................................... 86
4.2.8. Flowability of The Cement Paste Mixture ............... 87
4.3. Testing Result of Self Healing Evaluation .................... 92
4.3.1. Crack Width .............................................................. 92
4.3.2. Crack Depth ............................................................ 107
4.3.3. Direct Tensile Regain ............................................. 113
4.3.5. Alkalinity ................................................................ 127
4.3.6. XRD ........................................................................ 130
4.4. Discussions ................................................................... 138
4.4.1. Influence of Bentonite to the Self Healing .............. 138
4.4.2. Influence of BFS to the Self Healing ...................... 139
4.4.3. Correlation between w/c and healing ability ........... 140
4.4.4. Flexural - Tensile Strenght Relationships ............... 142
CHAPTER V CONCLUSIONS................................................ 143 BIBLIOGRAPHY ..................................................................... 145
LIST OF FIGURES
Figure 2. 1. Maximum crack width (functions of water pressure (h/d) according to Lohmeyer and Meichsner) ............. 9
Figure 2. 2. Causes of autogeneous self-healing ......................... 10 Figure 2. 3. Model for calculating the self-healing mechanism based on continued hydration ................................... 12 Figure 2. 4. Ca (OH)2 content based on cement type and additional pozzoland material ................................... 14 Figure 2. 5. Chemical structure of Montmorollonite .................. 17 Figure 2. 6. Self-healing [OPC90٪+CSA5٪+Geo 5٪] ................ 19 Figure 2. 7. A comparison X-Ray mapping between self healing zone and original zone .............................................. 19 Figure 2. 8. A comparison geopolimer gell in the self-healing zone with Hydrogarnet in original zone .................... 20 Figure 2. 9. Permeability Coefficient of Specimen using some mineral adimixture .................................................... 21 Figure 2. 10. γ Index value of Specimen using some mineral adimixture ................................................................. 22 Figure 2. 11. Flexural strength of cracked concrete using nanoclay for different curing conditions and precracking time ........................................................ 23
Figure 2. 12. Crack self-closing ratio .......................................... 24 Figure 2. 13. Cumulative heat production Q [J/g] for the different mixtures under investigation ..................................... 25 Figure 2. 14. Influence of carbonation degrees to the fillliing fraction of crack ........................................................ 26 Figure 2. 15. Faction minerals which close the crack ................. 27 Figure 2. 16. Influence of BFS replacement to Flexural strength concrete after cracking .............................................. 28 Figure 2. 17. Influence of BFS replacement to Splitting tensile strength concrete after cracking ................................ 28 Figure 2. 18. Influence of BFS replacement to compresif strength concrete after cracking .............................................. 29
Figure 2. 19. Maximum crack width for 100% healing .............. 30 Figure 2. 20. Crack healing percentage as a function of the initial crack width for A) fresh water and B) sea water ...... 31 Figure 2. 21. Chloride ion permeability of ECC mixtures using slag due to repetitive preloading ............................... 32 Figure 2. 22. Total crack closure rates of ECC mixtures with slag specimens due to self healing ................................... 33 Figure 3. 1. Flowchart of Research Methodology ...................... 36 Figure 3. 2. Measuring flow diamater of cement paste .............. 45 Figure 3. 3. Explanation of Sample Code ................................... 47 Figure 3. 4. Detail specification of briquet ................................. 48 Figure 3. 5. Dimension of Beam specimens ............................... 49 Figure 3. 6. Crack initiation by indtroducing teflon sheet as depth as 5 mm ........................................................... 49 Figure 3. 7. Detail of steel reinforcement ................................... 49 Figure 3. 8. Cylinder specimens ................................................. 50 Figure 3. 9. Coated specimens, a) cover side b) top side ........... 50 Figure 3. 10. Curing by covering specimens with wet burlap .... 52 Figure 3. 11. Introducing artificial crack, a) Cylinder specimens by using splitting test, b) beam specimens by using four point bending test .............................................. 53
Figure 3. 13. Water Imersion Curing .......................................... 54 Figure 3. 14. Schematic of Pulse Velocity Apparatus ................ 55 Figure 3. 15. Transmitter and receiver position for UPV measurement ............................................................. 56 Figure 3. 16. Typical arrangement for Measuring Crack Depth 57 Figure 3. 17. Example crack width graphic for calculating healing efficiency index ........................................................ 59 Figure 3. 18. Determine crack position ...................................... 59 Figure 3. 19. Choosing line button ............................................. 60 Figure 3. 20. Drawin line ............................................................ 60
Figure 3. 21. Showing crack width data ...................................... 60 Figure 3. 22 Determine crack position ........................................ 61 Figure 3. 23. Drawing poligon line ............................................. 61 Figure 3. 24. Typical arrangement for Four Point Bending Test 63 Figure 3. 25. Typical arrangement for direct tensile test according to CRD-C 260-01 ...................................................... 64 Figure 3. 26. a) Cylinder Specimens for cloride penetration,
b) Top Side, c) bottom side .................................... 67 Figure 3. 27. a) NaCl Flake, b) Dissolving NaCl flake in the water .......................................................................... 68 Figure 3. 28. a) Solution for Cloride penetration, b) Specimens were submerged in NaCl solution ............................. 68 Figure 3. 29. . Sampling for Cloride Ion Penetration Specimens 69 Figure 4. 1. SAI of OPC, Ca-Bentonite and BFS ....................... 77 Figure 4. 2. Diffractogram of BFS .............................................. 80 Figure 4. 3. Diffractogram of Bentonite ..................................... 81 Figure 4. 4. Particle Size Distribution of Bentonite .................... 84 Figure 4. 5. Cummulative Particle Size of Bentonite.................. 85 Figure 4. 6. Particle Size Distribution of BFS ............................ 85 Figure 4. 7. Cummulative Particle Size of BFS .......................... 86 Figure 4. 8. Flowability of the cement paste mixture ................. 89 Figure 4. 9. SEM image of BFS .................................................. 90 Figure 4. 10. Method to determine w/b for each mixture ........... 91 Figure 4. 11.Position of crack measurement point ...................... 93 Figure 4. 12. Evolution of the surface crack width over time for initial crack width 0 - 200 µm ................................ 94 Figure 4. 13. Evolution of the surface crack width over time for initial crack width 200 – 350 µm ............................ 95 Figure 4. 14. Comparison of material closing crack between mixture using BFS and mixture without BFS ........ 96 Figure 4. 15. . Evolution of crack width for B0S0 ...................... 98 Figure 4. 16. Evolution of crack width for B5S0 ........................ 99 Figure 4. 17. Evolution of crack width for B0S30 ...................... 99 Figure 4. 18. Evolution of crack width for B5S30 .................... 100
Figure 4. 19. β index for different mixtures on 28 days curing period ............................................................................. 103
Figure 4. 20. β index for different mixtures on 56 days curing period ................................................................... 103 Figure 4. 21. β index over time for each mixtures with initial crack width 0-200 µm .......................................... 105 Figure 4. 22. β index over time for each mixtures with initial crack width 200-350 µm ...................................... 105 Figure 4. 23. β index over the initial crack width ..................... 107 Figure 4. 24 Decrease in crack depth over time for each mixtures
............................................................................. 109 Figure 4. 25. Rate of Healing (α index ) over time for each mixtures
............................................................................. 110 Figure 4. 26. Side view of cracks on the concrete a). real crack pattern b) idealized crack pattern ......................... 112 Figure 4. 27. Tesile strenght before healing of some mixture on 28 age days after casting. ..................................... 115 Figure 4. 28. Tesile strenght regain after healing of some mixture on 56 age days after cracking ............................... 117 Figure 4. 29. Load – deflection curve of mixture B0S0 .......... 120 Figure 4. 30. Load – deflection curve of mixture B5S0 ........... 120 Figure 4. 31. Load – deflection curve of mixture B0S30 ......... 121 Figure 4. 32. Load – deflection curve of mixture B5S30 ......... 121 Figure 4. 33. Load – deflection curve of all mixtures .............. 122 Figure 4. 34. Model to analyze load – defelction curve ........... 123 Figure 4. 35. Crack occurence in load-deflection curve ........... 123 Figure 4. 36. Flexural stifness before (B) and after (A) healing process for different mixtures .............................. 126 Figure 4. 37. P cracking and P max for different mixtures ................ 127 Figure 4. 38. Ph value for each mixture ................................... 129 Figure 4. 39. Diffractogram of mineral closing crack for mixtures
B0S0..................................................................... 131 Figure 4. 40. Diffractogram of mineral closing crack for mixtures
Figure 4. 41. Diffractogram of mineral closing crack for mixtures B0S30 ................................................................... 133
Figure 4. 42. Diffractogram of mineral closing crack for mixtures B5S30 ................................................................... 134
Figure 4. 43. Comparison diffractogram for different mixtures 135
LIST OF TABLES
Table 2. 1. Permitted Maximum Crack Width .............................. 8 Table 2. 2. Composition of Bentonite (٪) ................................... 16 Table 2. 3. Chemical Compounds of Bentonite .......................... 17 Table 3. 1. Mix proportion for SAI test ...................................... 42 Table 3. 2. Mixture composition for each cement paste series ... 47 Table 3. 3. Rate of Increase in Net Deflection ............................ 62 Table 4. 1. Specific Gravity Test Result of OPC ........................ 71 Table 4. 2. Spesific Gravity Test Result of Ca-Bentonite ........... 72 Table 4. 3. Spesific Gravity Test Result of BFS ......................... 72 Table 4. 4. Density Test Result of OPC ...................................... 73 Table 4. 5. Density Test Result of Ca - Bentonite ...................... 74 Table 4. 6. Density Test Result of BFS....................................... 74 Table 4. 7. Saturated water content for each raw material .......... 75 Table 4. 8. Mixture compostion for each raw material ............... 75 Table 4. 9. SAI Test Result of Some Raw Materials .................. 76 Table 4. 10. Mineral Compound of BFS ..................................... 78 Table 4. 11. Mineral Compound of Ca - Bentonite..................... 79 Table 4. 12. Chemical Compound of Bentonite .......................... 82 Table 4. 13. Chemical Compound of BFS .................................. 83 Table 4. 14. Spesific Surface Area Properties............................. 87 Table 4. 15. Flowability test result of cement paste mixtures ..... 88 Table 4. 16. W/b for each mixture at contant flow 22 cm .......... 91 Table 4. 17. β index over time for B0S0 ..................................... 96 Table 4. 18. β index over time for B5S0 ..................................... 97 Table 4. 19. β index over time for B0S30 ................................... 97 Table 4. 20. β index over time for B0S30 ................................... 98 Table 4. 21. Existing crack depth for different mixtures .......... 108 Table 4. 22.Corrected crack depth for different mixtures ......... 108 Table 4. 23. Tensile strength before cracking ........................... 114 Table 4. 24. Tensile strength before cracking ........................... 114
Table 4. 25. Calculation of flexural stiffness of beams specimens for each mixtures ...................................................................... 125 Table 4. 26. P cracking and P max ratiofor different mixtures .......... 127 Table 4. 27. Ph measurement result for different mixture inside cement paste ............................................................................. 128 Table 4. 28. Ph measurement result for different result inside Crack ........................................................................................ 128 Table 4. 29. Percentage of mineral closing crack ..................... 136
CHAPTER I INTRODUCTION
Cracks are major problems, which always occur in buildings, such as reinforced concrete structures. Cracks occur because of some causes such as shrinkage, the differences in settlement, the difference in temperatures, chemical reactions, improper structural design, improper construction methods, and overloading (ACI 224.1R -07, 2007). Since the probability of crack occurrence is very high, the crack has to be repaired before it propagate widely. If there is no immediate repair, it can lead to the strength deterioration, corrosion of the concrete reinforcement, and also the decrease in concrete durability (Jaroenrat Prom, 2011).
If the crack’s position can be observed and reached, it can be repaired as soon as possible after its positions are detected. However, if the cracks occur on an undetected position such as the drainage channel/irrigation, dam structures, foundations, sheet piles, bridge abutments, tunnel structures and other underground structures, new approach is needed to solve this problem. The Self-healing concrete is a new approach which can solve crack problems on undetected structures (Ahn et al. 2009). Self-healing concrete is a type of concrete, which can heal cracks by its self automatically, when a crack occurs in the concrete structures.
Self-healing concrete approach has been widely studied by many researchers to solve crack problems on the concrete structure. Some mechanism such as swelling and recrystallization mechanism (Ahn, 2010), carbonation reaction, continued hydration (Tittleboom, 2012), bacteria metabolism to produce CaCO
3 (Jonkers, 2009), low
pozzolanic reaction (Hung, 2013) are common mechanisms, which have been proven to be able to generate self-healing properties. Generally, self-healing mechanisms can be divided into four principal mechanisms, including physical mechanism (swelling process), chemical mechanisms (hydration process and carbonation process), biological mechanism and mechanical mechanisms (Reinhardt et al, 2013). From the four principal mechanisms above, swelling process, carbonation process and hydration process have dominant effect to the self-healing process of cracks in concrete, in terms of crack width and water permeability.
Swelling process can generate self-healing properties in cracked concrete. Application of some clay minerals containing Montmorilonite mineral can be used for self- healing concrete application, in terms of swelling process (Ahn, 2010). It is caused by high ion-exchange capacity of Montmorilonite mineral, which can contribute swelling mechanism (Muurinen, 2011). Crack in concrete containing 5% geomaterial has high self-healing efficiency, compared to the normal concrete by using water immersion curing. It is due
to diffusion of Al ion and Si Ion (Ahn, 2009). Furthermore, application of nanoclay in the concrete can decrease the water permeability coefficient on 28 age days and 60 age days after cracking up to 0.18 on 0.90 respectively. Besides that, it can decrease crack width up to 0.70 on 28 age days after cracking (Jiang, 2015). In the other case, nanoclay/bentonite has water retaining capacity. It means that bentonite can adsorb some water, and the water will be retained by bentonite in the concrete matrix. In the dry condition case, the montmorilonite will shrink and release some water. This water is very beneficial for carbonation reaction and continued hydration reaction to produce self-healing properties. In case of mechanical regain, crack in the concrete containing nanoclay has a high deflection capacity after cracking, compared to the normal concrete (Qian, 2010).
Besides the swelling process, the self-healing mechanism is also influenced by the carbonation reaction.
This process occurs, when calcium ions (Ca ) from the
2 dissolved in the water. This reaction produces CaCO
crystals, which can fill up the cracks. The amount of Ca ion is very influenced by Ca(OH)
2 resulted from the cement
hydration (Edvarsen, 1996). The amount of Ca(OH)
influenced by the amount of pozzolan replacement and pozzolan reactivity used in cement (Reinhard et al, 2013). Thus, replacement some clinker cement with some materials such as pozzolan can decrease the amount of Ca(OH) and
Ca ion. Furthermore, precipitation of CaCO
3 will decrease, and it can contribute decrease in self-healing properties.
However, some approach can be used to increase the amount
of Ca ion. Application of nanoclay containing Ca-
2+ Montmorilonite can increase Ca ion (Fernandez, 2014). 2+
Increasing Ca ion can accelerate CaCO
3 precipitation. It was
proven by Muharam (2013), that combination of Ca-bentonite and Alkaline solution Ca(OH)
2 could adsorb more CO 2 gases,
compared to the conventional method. The absorption value of Ca-Bentonite containing Ca-Montmorilonite is 8.9-9.9%. Thus, Ca – bentonite is very beneficial to produce self-healing properties.
Besides the swelling process and carbonation process, the self-healing mechanism is also influenced by the hydration reaction, both continued hydrations of unreacted clinkers and hydration reaction of some latent hydraulic material such as Blast Furnace Slag (BFS). According to Zhong (2012), not all the clinker cement has been hydrated within the first 28 age days after mixing. Thus, the unhydrated clinker cement is available in the concrete matrix. If the crack occurs, unhydrated clinker cement reacts with water entering inside of crack to continue its hydration. The result of this reaction is C- S-H gel which can fill up the crack. Application of some byproduct materials such as Blast Furnace Slag (BFS) is potential used for self-healing concrete, because it has latent hydraulic properties. BFS has slow hydration reaction compared to clinker cement hydration (Lothenbach, 2012). BFS also has latent hydraulic properties. It means that, besides ph to activate its particles. High Ca(OH)
producing high ph can accelerate hydration reaction of BFS particles (Huang, 2012). Application of BFS as partial cement replacement of clinkers can contribute decrease in hydration heat rate, compared to the normal clinker. High replacement of BFS can contribute hydration heat rate more decrease (Nasir, 2014). Although hydration heat rate of clinker cement is higher than clinker cement containing BFS, but this process only occurs within the first 45 hours after casting. (Tittleboom, 2012). This property of BFS is very beneficial to produce self-healing properties, in terms of continued hydration mechanism (Oliver, 2013). This hydration product is mainly identified as C-S-H gel, Aft, and AFm. Hydration product can be increased by Ca(OH)
2 activation process
before BFS particle mixes together with other materials (Huang, 2012). The result shows that application of BFS as partial cement replacement can close crack completely with maximum crack width 408 um (Palin, 2015).
Based on problems above, bentonite and BFS have different mechanism to heal cracks. However, there is little information about self-healing properties of the cement paste incorporating bentonite and BFS, especially in terms of mechanical regain. In this research, self-healing property of cracked cement paste is discussed, including physical properties (decrease in crack width and crack depth), chemical properties (mineral of healing product), and mechanical regain properties (direct tensile strength and flexural strength). Thus, in this final project report will be discussed the research results that had been conducted, entitled "Influence of bentonite and blast furnace slag to the self-healing behavior in cracked cement paste."
1.2. Research Problems
The problems of this research are described as follows:
1. How bentonite and BFS influences self healing propertis of cracked cement paste? a. How the bentonite and BFS influences the crack width of cracked cement paste? b. How the bentonite and BFS influences the crack depth of cracked cement paste? c. How the bentonite and BFS influences the tensile strength recovery of cracked cement paste? d. How the bentonite and BFS influences the felxural stiffness recovery of cracked cement paste?
2. How about the self healing mechanisms occur in cement paste incorporating bentonite and BFS as a partial cement replacement?
1.3. Research Boundaries
In this research, there are a few problem's boundaries, include:
1. The self-healing is evaluated only by measuring four parameters, include crack width, crack depth, direct tensile recovery, and flexural stiffness recovery of the cement paste after cracking.
2. In this study, flow table test is conducted to determine w/c for each mixture series to get constant consistency with constant value 22 cm.
3. Cement which is used in this research is cement type 1 (Ordinary Pprtland Cement)
4. There’s no economical aspect, which is discussed in this final project report.
1.4. Research Objective
The objective of this research are described as follows:
1. To analyze the influence of bentonite and BFS to the self healing behavior in cracked cement paste.
a. To analyze the influence of bentonite and BFS to the crack depth of cement paste after cracking.
b. To analyze the influence of bentonite and BFS to crack width of cement paste after cracking.
c. To analyze the influence of bentonite and BFS to
d. To analyze the influence of bentonite and BFS to flexural regain of cement paste after cracking.
2. To analyze the self healing mechanisms occurre in cement paste incorporating bentonite and BFS as a partial cement replacement
Benefits of this research are described as follows:
1. As a reference to next researchers about self-healing properties of cracked concrete.
2. This research is expected to reduce and solve crack problems, which occur in concrete structures, especially for undetected and unreached crack position.
3. As a supporting research to develop alternative cement products, which can be used to overcome the crack's problem in concrete structures.
CHAPTER II LITERATURE REVIEW
2.1. Crack on the Concrete Structures
Cracks can be classified as structural crack and non- structural crack. Structural cracks are due to improper structural design or also overload-capacity. Non-structural cracks are mostly due to the stress, which is induced internally in materials. This non-structural crack leads to weak the structures indirectly. Crack occurrence in the field can reach up to 50% from the total type of structure damage (Saputra et al, 2011).
According to Ghafur (2009), cracks can be identified by using three parameters, including crack width, crack length and crack pattern. Generally, crack width is very hard to be measured, because it has an irregular shape. In hardening concrete, micro crack is very hard to be measured because of the crack width is too small. To observe crack width of micro cracks, microscope is usually used with varies crack width between 0.125 - 1.0 μm (eight hour after casting). Minimum crack width which can be observed by the eye is 0.13 mm (0.005 in), and it is belonged to micro cracks. Micro cracks will propagate widely, when there’s no immediate repair.
Based on ACI 224 R – 01, permitted maximum crack width is determined based on type of concrete structures and environment condition of concrete. For the structures which are influenced by corrosion, greatest crack widths are limited 0.15 mm. For indoor and impermeable structures, maximum crack widths are limited 0.41 mm. Permitted maximum crack width can be seen in Table 2.1.
According to ACI 224 1R -07, cracks in concrete structures occur because of some causes such as shrinkage, the difference in temperature, chemical reaction, improper structural design and construction method, and overloading.
Table 2. 1. Permitted Maximum Crack Width Type of structure and Limit of crack No Enviroment width (mm)
1 Indoor strucrures, structure in dry
air enviroment, water impermeable structures
2 Structures contact with water
3 Outdoor structures, middle
0.30 humidity, no corrotion effect
4 Outdoor structures, high
humidity, structures are influenced by chemical reaction
5 Structures with high humidity,
0.15 structures are influenced by corrotion (snow/ice, sea water)
Source: ACI Commite 224R (2001)
2.2. Conditions for Self-Healing
According to Heide (2005), there are several condition which can contribute self healing process. Some conditions are very important for self healing process. Some conditions are: a. Water, water is very important to the all of self healing mechanisms. Thus if there’s no water, self healing process will not occure. It had been reported by Lauer (1956) that humidity enviroment 95٪ could decrease healing process in cracked concrete.
b. Cracks width, self-healing can occure for a small cracks width. Thus, in the large crack width, self healing prosess still occur, but crack close incompletely.
c. Water pressure, if the water enter throuh inside of the cracks rapidly, the self-healing process will not occure.
This condition is usualy described as a maximum ratio between water pressure head and thickness of the cracked concrete as shown in Figure 2.1.
Although, there are some requirement for self healing condition, but there is litlle information which is used to maximize self healing process, both for water pressure and cracks width. But Van Breugel (2003) reported that limit of a maximum cracks width is determined based on the water pressure which can enter inside of the cracks, such as shown in the Figure 2.1.
Figure 2. 1. Maximum crack width (functions of water pressure
(h/d) according to Lohmeyer and Meichsner) Maximum crack width 0.2 mm is limits of cracks width which can be healed perfectly for h/d less than 10. If cracks width greater than 0.2 mm, self healing process still occur, but crack close incompletely. In addition for h/d greater than 10, cracks width is limited between 0.05 - 0.20 mm, in order the self healing process occur completely.
2.3. Self-Healing Mechanism
Generally, there are 2 mechanisms of self healing on concrete, including autogeneous healing and autonomous
healing. Autogeneous healing is the self healing process that
the recovery process uses material components that could otherwise also be present when not specifically designed for self healing. In the other hand, Autonomous healing is the self healing process that the recovery process uses materials components that would otherwise not be found in the material. According to Reinhardt et al (2013), causes of autogeneous self-healing are divided into 3 causes, including physical cause, chemical causes, and mechanical causes. That three main mechanisms are shown in the Figure 2.2.
Figure 2. 2. Causes of autogeneous self-healing
Source: Reinhardt et al (2013) Physycal cause is due to the swelling process of
Hidrated Cement Paste (HCP) or other additives materials which have swelling ability. The swelling of HCP occur, when water molecules are adsorbed by HCP and fill up the gap between cracks surface. But this mechanism produce low healing effectiveness. This is proven by reinhard (2013), that permeability on the crack area decrease less than 10%, in term of swelling process of HCP. But for the specific material which have swelling ability, permeability on the crack area could decrease up to 90٪.
While in chemical process causes are devided into 2 mechanisms, including continued hydration of Unhidrated Cement Paste (UCP) and carbonation reactions. The continued hydration process of UCP needs water to continue its hydration. When cracks occur, water will go through inside of cracks and react with UCP, in term of hydration up to 2 times from diameter of clinker cement. Thus, continued hydration of UCP close cracks incompletetly. But if cracks width less than or equal to 0.1 mm and by the assumption that HCP can swell and hydrate simultaneously, cracks can close completely. But if cracks width greater than 0.10 mm, the effects of this mechanism is very small.
Beside continued hydration, self healing process based on chemical causes are also contributed by carbonation reaction. This carbonation reaction occur, when
Ca ion react with carbonat (CO3 ) ion to precipitate
3 Calcium Carbonate (CaCO ) crystal. This Calcium
3 Carbonate (CaCO ) is white crystal which can fill up the 2+
cracks. This Ca ions are suplied from Ca(OH) which is
resulted from cement hydration. And this carbonat (CO3 ) ions are came from water entering inside of crack. This carbonation reaction is influenced by temperature, ph, and reactants concentration. This carbonation reaction has high healing effectiveness, when compared to the other mechanisms (Edvarsen, 1996).
While mechanical causes are divided into 2 mechanisms, including particles which are carried by water and fracture of concrete particle which can blockage the cracks. But this two mechanisms give low effect to the self healing process of the cracked concrete.
2.4. Self-Healing Mechanism with Continued Hydration
Edvardsen (1996) made analytical calculations to simulate hydration process of the clinker cement. Edvardsen concluded from several theories, that continued hydration could close crack completely, if the initial crack width is less than 6µm. Thus, maximum cracks width which can be healed perfectly by this mechanism is 6µm. Model used for calculating continued hydration process of clinker cement is shown in the Figure 2.3.
a. All these particles cements have same diameter size 50
................................................( 1 ) ..........................................( 2 )
) ⋅ (1 - α) = (31.5 – 25) ⋅ 0.95 = 6 μm Thus, only cracks width 6 μm or less than 6 μm can
Δw = (r
⋅ r = 31.5 μm
= 2V r
= 4/3 ⋅ π ⋅ r
Edvardsen (1996) used some assumptions to calculate hydration of clinker cement, as follows:
V = 4/3 ⋅ π ⋅ r
The calculations had been done by Edvardsen (1996) and describe as follows:
based on continued hydration (Source: Edvardsen, 1996)
Figure 2. 3. Model for calculating the self-healing mechanism
c. Crack occur between aggregates and cement particles, so one side of crack is aggregate particle surface, and other one is cement particles surface.
= 2 V
b. After the hydration process occur completly, the volume of hydration particles cement which has been hydrated is 2 times from initial volume of undydrated cement particles before hydration process. V
µm (ro = 25µm)
In the concrete material, not all cement particles are hydrated at the beginning time after casting. Thus, the unhydrated clinkers are still available in concrete matrix. In most concrete with low w/c, the amount of unhydrated cement particles can reach up to 25٪ (Breugel, 2007). This unhydrated cement particles are still available in concrete matrix and can survive until long time. So, when cracks occur, the self-healing whic is contributed by continued hydration can occur (Li, 2007).
2.5. The influence of Pozzoland to Ca(OH) content
2 It has been explained on the sub chapter 2.3 that
healing effectiveness is influenced one of them by the carbonation reaction. The carbonation reaction is very
2 influenced by the amount of Ca(OH) in the concrete matrix.
Additional pozzoland material is able to reduce the amount
2 of Ca(OH) in the early age of concrete (Reinhard, 2013).
2 Reducing Ca(OH) content is able to decrease self healing
process. This fact not only occur on cement Portland, but also on the blast furnace slag cement. Additional fly as, both in cement portland and blast furnace slag cement are able to
reduce the amount of Ca(OH) at the age 365 days. The
amount of Ca(OH) for cement portland and blast furnace slag cement are 8 gram/100 grams and 3 grams/100 grams respectively. So pozzoland which has low reactivity is more recommended to produce self healing behavior in concrete. The influence pozzoland fly ash to the Ca (OH)
concentration can be seen in Fig. 2.4
Figure 2. 4. Ca (OH)2 content based on cement type and
additional pozzoland material (Source: Reinhard et al, 2013)
2.6. Characteristics of Bentonite Clay
Bentonite is clay mineral which contain monmorilonite minerals and belong to dioktahedral group and also smectite group. Bentonite contains around 80٪ monmorilonite and others minerals such as kaolonite, illite, feldspar, gypsum, quartz, calcium carbonate in small portion. Bentonite is formed by chemical and mechanical process of rock which is influenced by weather (on the alkaline environment). That rocks are generally came from volcanic eruption, and also came from andesite, riolit, basal and others. Almost of them belong to tertiary rocks. Bentonite is spread in several area in Indonesia such as some area in Java, Sumatra, East Kalimantan and Sulawesi (Puslitbang Tekmira, 2005).
Based on Puslitbang Tekmira (2005), Bentonite is clay mineral which consist of montmorillonite minerals and other minerals such as kwarsa, kalsit, dolomite, feldspars, and other minerals in small portion. Montmorillonite is group of smectit with general chemical formula
(Mg,Ca)O.Al O .5SiO .nH O. Bentonite is different from others clay minerals, because it has almost 75% Montmirilonite minerals. Based on swelling ability of montmorilonite mineral, bentonites are divided into two categories, including:
a. Na bentonite Na - bentonite has high swelling capacity up to eight times from the initial volume, when it’s immersed into the water. In the dry condition, Na bentonite has white colour or cream colour. In the wet conditions, Na bentonite has polishing color. Suspension of Na- bentonite colloid in water has pH value 8.5 - 9.8.
b. Ca - bentonite Ca–bentonite has low sweeling capacity when it is compared with Na–Bentonite. But Ca–bentonite has high adsorbtion capacity after it has been activated. In dry condtion, Ca–bentonite has gray, blue, yellow, and red colour. Suspension of Ca bentonite colloid has pH value 4.0 - 7.0.
Composition of Bentonite
As described above, bentonite has swelling capacity. It is mainly caused by montmorilonite minerals. When montmorilonite mineral contact with the water, there will be an ion exchange process between bentonite ion and water ion. This ion excanghe process contribute to the swelling properties of bentonite.
There are some type of bentonite. Based on composition and the initial discovery, bentonites are divided into NAGRA bentonite MX record-80 from US, Kunigel VI from Japan and Berapaw from Canada. Composition of each bentonite type are shown in Table 2.2. Percentage of Na - montmorolinite is higher than the other mineral in bentonite. Na - montmorolinite mineral has more high
- 3.0 – 3.5 - Dolomit - 2.0 – 3.8 -
< 1 - - Glimer
cation which bound with 6 hydroxyl ion (OH
cation which bound with 4 oxygen atom. While octahedral layer consists of Al
According to Bergaya (2006), Montmorillonite (Mt) that is found in bentonite consists of 2 two tetrahedral layer and one octahedral layer. Tetrahedral layer consist of Si
Source: Suryantoro, et al (1998)
< 1 - - Lain - lain 2.0 - -
0.4 - Minor Kaolinite
1.4 2.1 – 2.6 Minor Organic Carbon
Pirit 0.3 0.3 – 0.7 - Feldspar/plagioklas 5 – 8 2.7 – 5.5 Minor Kalsit/Karbonat
10 Quartz 15.2 29 – 38 Minor
80 Illite - -
Na – montmorillonite 75 46 – 49
Table 2. 2. Composition of Bentonite (٪) Mineral MX (AS) Kunigel V1 (Jepang) Berapaw (Canada)
2.7. Chemical Structure of Montmorolinite
- ). When Montmorilonite (Mt) minerals contact with water, water molecules will enter to the area between oktahedra layer and tetahedra layer. The ion from water and cation from bentonite layer will do iteraction and ion exchanges process. This mechanism cause bentonite can swell. Swelling capacity of bentonite can reached up to 15 - 18 times from the initial volume before bentonite contact with water (Lie, 1995). To understand this swelling mechanism, chemical structure layer of montmorillonite can be seen clearly in the
Figure 2. 5. Chemical structure of Montmorollonite
2 O 7.2 % 7.22 %
2 O 0.4 % 0.55 %
2 O 2.2 % 0.50 %
MgO 1.3 % 3.30 % Na
3.9 % 5.30 % CaO 0.6 % 3.68 %
(Source: Li 1995)
19.8 % 17.33 % Fe
2 61.3 – 61.4 % 62,12 %
Table 2. 3. Chemical Compounds of Bentonite
Oksida Na – Bentonite (%) Ca – Bentonite (%)
(Source: Puslitbang Tekmira ESDM, 2004)
2.8. Autogenous Healing Concrete using Geomaterial
Ahn and Kishi (2009) reported about influence of geomaterial incorporating expansive agent to the self healing behaviour of cracked concrete by using contant water per
binder w/b = 0.45. The geomaterial contains SiO and Al O about 71.30% dan 15.4 % respectively. From the XRD analysis, it is known that geomaterial A contain sodium
4 Silicate Aluminum Hidroxyde [Na Al Si O (OH) ] mineral which is identified as montmorillonite mineral.
Beside montmorillonite mineral, Geomateria A is also identified as feldspar, and quartz in small portion. Geomaterial is used in this research, because it has montmorillonite minerals which have swelling capacity. From the research result, it is found that combination of cement paste [OPC90% + CSA5% + Geo-material 5%] give the best healing capacity. Initial crack 0.2 mm could be healed perfectly after 28 age days by using this composition as shown in Figure 2.6. Healing product closing cracks are observed after 14 age days, and cracks are almost closed perfectly after 200 age days curing time.
X-Ray mapping is carry out by Ahn and Kishi (2009) to analize mechanism of self healing occurred in the spcimens. From testing result, mineral closing crack is almost identified as Alumina Silicate as shown in Figure 2.7. Self healing zone and original zone are observed to understand mechanism in the two zone. Self healing zone is identified as gehelite phase (CASH) with high alumina ion when compared with original zone. So it can be concluded that
calcium Hidroksida (Ca(OH) ) which is resulted from hydration reaction could activate geomaterial A to formed Calcium Alumino Silicate Mineral. This minerals is mineral particle which can close crack on the specimen.
Figure 2. 6. Self-healing [OPC90٪+CSA5٪+Geo 5٪]
Source: Ahn and Kishi (2009)
Figure 2. 7. A comparison X-Ray mapping between self
healing zone and original zone Source: Ahn and Kishi (2009)
According to Ahn and Kishi (2009), alkaline activator
of geomaterial A in presence of Ca(OH) which is resulted from hydration reaction led to form amorphous Calcium Aluminosilikat gell, which have same characteristics withFigure 2.8 geopolimer gell in high alkaline environment.
shows the difference between geopolimer gel in the self healing zone and hydrogarnet in the original zone by using scaning electron microscope (SEM). Geopolimer gell size in self healing zone is less than 2µm. In addition, the modified geopolimer gell in self healing zone is structured by dense phases as compared to Hydrogarnet phases in original zone.
Figure 2. 8. A comparison geopolimer gell in the self-healing
zone with Hydrogarnet in original zone (Source: Ahn and Kishi, 2009)
From the research which have been conducted by Ahn and Kishi (2009) above, it is known that Geomaterial A have ability as healing agent, but Ahn and Kishi didn’t explain specifically about this Geomaterial.
Beside recrystalisation and swelling term, bentonite in the concrete matrix also has inner water retaining capacity and inner water supply capacity. According to Jiang et all (2015), permeability coefficient of cracked concrete which contain swelling material (bentonite) could decrease, when compared to control specimens. It is caused by swelling term, and inner water retaing term. Swelling properties of montmorilonite mineral fills up the gap between cracks, but less dense. So water entering crack also can decrease. In the other hand, bentonite also has water adsorbtion capacity/inner water retaining term. Because of that, some water entering crack will be adsorbed by bentonite, and cause decreasing of water through crack.
Figure 2. 9. Permeability Coefficient of Specimen using
some mineral adimixture Souce: Jiang et all, 2015
Self healing concrete using bentonite is also studied by Jiang et al (2015) in term of crack width. The observation result is shown in figure 2.10. The self healing process in term of cracks width is analyzed by index which is calculated based on ratio between decreasing of crack width at time t and the initial crack width. By using swelling material (bentonite), index value is higher than control specimen, although index of specimen using bentonite is less than other additive material. But from the permeability coefficient, utilization of bentonite had second lowest permeability coefficient than the other additive mineral and specimen control. It can be analized that swelling can only blockage crack, when the water is available inside of cracks. If the inside of crack is in dry condition, retained water on bentonite will release, and bentonite will shrink. Because of that, the observation of crack width showed that crack closing rate of speccimens using swelling material is lower than the other additive mineral. Releasing of retained water from bentonite is very beneficial to generate self healing mechanism in term of continued hidration and carbonation process, especially for cracked concrete in dry environment.
Figure 2. 10. Index value of Specimen using some mineral
adimixture Souce: Jiang et all, 2015
According to Qian et all (2010), utilization of nanoclay (bentonite) had higher flexural strength with variation of curing condition and precraking time compared to reference specimen. This fact is mainly caused by continued hydration of unhydrated cement paste. It can be observed that specimen which is cured in air condition had highest flexural strength when compared to the other curing condition. In the air condition, there is small amount of water, so retained water inside bentonite could suply more water to continue hydration process. These continued hydration process can generate self healing process in term of flexural regain. If precracked time 56 days, the flexural strength regain is lower than concrete reference. It is caused by all of cement clinker has been hydrated before age 56 days. So self healing process in term of flexural regain decrease after 56 age days.
Figure 2. 11. Flexural strength of cracked concrete using
nanoclay for different curing conditions and precracking time Source: Jiang et all, 2015
2.9. Blast Furnace Slag as Autogenous Healing material
Blast furnace slag can be used as autogeneous healing material in concrete because of its latent hydraulic properties. Autogenenous healing behavior of cement paste incorporating BFS had been studied by Tittelboom et al (2012) in term of crack width and cumulative head produce by hydration process.
According to Tittelboom et al (2012), for crack
Figure 2.12), replacement
width in the range of 0 – 125 m ( some clinker cement with BFS resulted lower healing effectiveness (shown by value) compared to OPC (CEM
I). This fact is contributed by amount of Ca (OH)
2 in cement paste matrix decrease because of BFS replacement.
So white crystal which is deposited in crack surface is also decrease.
Figure 2. 12. Crack self-closing ratio
(Source: Tittelboom et al, 2012) Beside of crack closing rate, the cumulative heat production which is measured by the TAM AIR calorimeter is also analyzed by Tittelboom et al (2012). The result is shown in Fig. 2.13. It is noticed that in the beginning (first 45 h of rewetting), most heat is produced by the crushed CEM I (Ordinary Portland cement) specimen. As cement is a hydraulic binder, unreacted cement grains, present in the crushed cement paste, react fast upon contact with water and hereby release hydration heat.
Blast furnace slag is a latent hydraulic binder material. Thus, cement paste specimen containing blast furnace slag reacted somewhat slower than the CEM I specimen.
However, after around 40 h, the heat production rate of the CEM I specimen diminishes rapidly while specimen containing blast furnace slag still produce more heat and continue to react at the same rate. After 45 h and 75 h, respectively, the cumulative heat production of the 50 BFS and the 85 BFS mix, becomes higher than the values noticed for the CEM I specimen.
Increasing the percentage of blast furnace slag does not seem to increase the cumulative heat production within the first 140 h after mixing. This is noted as the curve which is obtained for the 85 BFS mix is plotted below the 50 BFS mix curve. Although the heat production rate is almost same (as both curves show a parallel course), initially more heat is produced by the 50 BFS mix. This may be caused by the
fact that less Ca(OH) becomes available from the hydrated clinker to activate the blast furnace slag reaction, when higher replacement percentages are used. Although, the cumulative heat production after 1 week is lower for higher percentages of blast furnace slag, it should be noticed that due to the fact that more unhydrated slag particles will be available in mixes with high amounts of blast furnace slag, hydration may continue for a longer period.
As the composition of a CEM III cement is similar to the composition of the mixture where 85% of the cement weight is replaced by blast furnace slag, it can be expected that both heat production curves follow the same course which is also observed
Figure 2. 13. Cumulative heat production Q [J/g] for the
different mixtures under investigation (Source: Tittelboom et al, 2012) Autogeneus healing behavior of cement paste with blast furnace slag as partial cement replacement also has been studied by Huang et al (2014). The healing mechanism is mainly influenced by physical and chemical mechanisms. Cement with 66% BFS as partial cement replacement able to close cracks width which is occurred in concrete. Self healing process in term of closing crack width is due to some chemical reaction occurred inside of the cracks. Result of this chemicals reaction are C – S – H, ettringite, hydrogarnet and OH-hydrotalcite. But the highest percentage mineral closing crack is identified as C - S – H gell from the other minerals. The formation of C - S – H gell
fraction is due to BFS particles which is activated by Ca ion from the alkaline environment of the concrete. After BFS particles has been activated, BFS can react with water to produce C – S – H gell. The filling fraction mineral of the craks are shown in Figure 2.14. The highest mineral closing crack is C - S – H, and then followed by Etrringite minerals,
6 Hydrotalcite minerals and C AH in small amount.
Figure 2. 14. Influence of carbonation degrees to the
fillliing fraction of crack According to Huang et al (2014), fraction of minerals formed in cracks could change when carbonation reaction occurred inside cracks. Figure 2.15 showed the influence of carbonation degrees to self healing effectiveness by using BFS as patial cement replacement. In the initial phase, when carbonation degree 0 – 2%, amount of filling fraction of crack increase from 54% to 56%. But this value decrease from 56% to 47% when the faction mineral inside cracks has been hydrated perfectly.
Curing period (days) Figure 2. 15. Faction minerals which close the crack
Source: Huang et al, 2014 Self healing mechanims with Blast Furnace Slag
(BFS) is also studied by Sukumar and Depaa (2013), where the self-healing parameter is analyzed based on compresif strenght, flexural strenght and splitting tensile strength after cracking. BFS replacement used is 0%, 35%, and 35%. From three parameter of self healing, optimum percentage BFS replacement is 35%.
Figure 2. 16. Influence of BFS replacement to Flexural
strength concrete after cracking (Source: Sukumar and Depaa, 2013)
Figure 2. 17. Influence of BFS replacement to Splitting
tensile strength concrete after cracking (Source: Sukumar and Depaa, 2013)
Figure 2. 18. Influence of BFS replacement to compresif
strength concrete after cracking (Source: Sukumar and Depaa, 2013)
According to Sukumar and Depaa (2013), self healing process is totally influenced by continued hydration of unhydrated BFS particles. So if crack occur, hydration process run. This hydration results had characteristics as
bonding agent as well as filling agent. Bonding agent
function can be seen from the inceasing of compresif strength after cracking with 35٪ BFS replacement.
Palin et all (2015) quantified the autogenous healing capacity of ordinary Portland cement (OPC) and blast-furnace slag (BFS) cement mortar specimens submerged in fresh- and sea-water. After 56 days, BFS cement specimens in sea-water healed 100% of initial cracks up to 104 μm, while OPC specimens healed 100% of initial crack up to 592 μm. In fresh-water, BFS cement specimens healed 100% of initial cracks up to 408 μm, while OPC specimens healed 100% of initial cracks up to 168 μm. Differences in performance are attributed to the amount of calcium hydroxide in these mortars and specific ions present in the sea-water.
Figure 2. 19. Maximum crack width for 100% healing
(Source: Palin et al, 2015)Figure 2.20 shows the compressive strength of
mortar cubes over time. Before submersion, CEM I specimens began with somewhat higher compressive strengths than CEM III/B specimens, and these roles are reversed by day 28 with CEM III/B specimens which have slightly higher compressive strengths than CEM I specimens. 28 days after casting specimens are submerged in either fresh- or sea-water. From day 28 to 168, the mean compressive strength of CEM I and CEM III/B specimens submerged in fresh-water stabilised at 55–60 MPa, with CEM I specimen have a standard deviation 22 MPa. Specimens submerged in sea-water however showed a markedly different tendency. The mean compressive strength of CEM III/B specimens submerged in seawater stabilised much like those in fresh-water at 60 MPa, while the strength of CEM I specimens in sea-water decreased from day 28 to 168 from 55 to 45–50 MPa. (Strength decrease more than 10%). Unsubmerged CEM I specimens maintained value of a compressive strength of about 55 MPa. Thus, sea-water curing resulted higher healing efficiency, compared to other curing methods.
Figure 2. 20. Crack healing percentage as a function of the
initial crack width for A) fresh water and B) sea water (Source: Palin et al, 2015)
Sahmaran et al (2015) also studied about self healing concrete with blast furnace slag in ECC mixtures, especially in term of chloride ion permeability and crack
closure rate. From the RCPT result shown in for the virgin specimen (uncracked concrete), chloride ion permeability is decrease undergoing 50W/D cycles. It is mainly caused by availability of unreacted slag particles in concrete matrix that requiring longer period to react and produce hydration product such as Calcium Silicate Hydrate (C – S – H) gell through continued hydration. In the the other hand, chloride ion permeability of pre – load
specimen (cracked concrete) is increased up to 77% (
2.21) of the initial reading after five preload applications
aand corresponding W/D cycles. This behavior can be attribute to greater fiber-matrix frictional bond strength and fractures toughness off ECC specimen using Slag, which may have significantly reduced the chance of multiple crack occurrence and increased crack width with application of repetitive preloading.
Figure 2. 21. Chloride ion permeability of ECC mixtures
using slag due to repetitive preloading (Source: Sahmaran et al, 2015)
From the crack closure rate, ECC mixtures with slag showed decreasing of crack width both in 3-days- preload pecimen and 28 days preload specimen. It can be shown from Figure 2.22 that crack closure rates is 42 – 51 % in the 10 W/D cycles, then value of crack closure rates decreased by increasing number of cycles. Morever, the crack closure rates of 3-days-preload specimen is higher than 28-days-preload specimen. This two fact above are due to the amounts of unhydrated cementious materials which are expected to be present in ECC mixtures with slag. In the 3-days-preload specimens, amounts of unhydrate cementious material is higher than 28-days- preload specimen. Because of that crack closure rate curve of 3-days-specimen is take place above of crack closure rate curve of 28-days-specimen. Beside that, by increasing of W/D cycles, the amount of unhydrated cementious material also decreased, and causing crack closure rates
Figure 2. 22. Total crack closure rates of ECC mixtures
with slag specimens due to self healing (Source: Sahmaran et al, 2015)
CHAPTER III RESEARCH METHODOLOGY To solve the problems in this research, flow chart of research
methodology is designed as shown in Figure 3.1
Figure 3. 1. Flowchart of Research Methodology
3.1. Literature Riview
Literature riview include riviewing some journals, books, proceedings, and codes related to self healing mechanisms, autogeneous healing, characteristic of bentonite both physical and chemical properties of bentonite, characteristic of blast furnace slag especially for chemical properties, self healing behavior of concrete incorporating blast furnace slag, self healing behavior of concrete incorporating bentonite, self healing product of some research related to bentonite and BFS, and some standart testing and
3.2. Preparation of Materials
Preparation of raw materials, include :
a. Ordinary Portland Cement (OPC) Cement whic is used in this research is cement type 1/Ordinary Portland Cement (OPC) that is gotten from PT. Semen Indonesia, Tbk. OPC is used in this research because, there is no influence of healing process from others material such as pozzoland material in PPC or other composite material in PCC.
b. Bentonite There are two types of bentonite, including Na – Bentonite and Ca – Bentonite. However, Ca bentonite is choosen in this reserach because it has low shrinkage properties. The bentonite is gotten from PT. Nusa Indah Megah.
c. Blast Furnace Slag Blast furnace slag which is used in this reseach is gotten from PT. Krakatau Steel Industri, Tbk. Real condition of BFS is granulated particles (ground granulated blast furnace slag). Because of that, BFS must be grinded firstly for 12 hour by using Ball mill to get specific
2 surface area of BFS particle arround 3000 cm /gram.
d. Water The water used in this research is tap water.
3.3. Analisys of Raw Materials Properties
3.3.1. Method to Determine Specific Gravity
This method is conducted according to ASTM C188 - 89. This method is conducted to determine specific gravity of each materials which is used in this research, that’s OPC, bentonite, and BFS. Spesific gravity of fine material is defined as the ratio of its particle weight to the total volume of particles. Volume of particle is calculated based on volume of water according to Archimedes Law.
2. Specimen chamber
3. Pipet and Funnel
4. Balance with precision 1 gram
1. Measure weight of material sample as weight as 150 gram by using balance
2. Prepare pycnometer with volume capacity 500 mL Then measure weigth of picnometer (W
3. Introduce sample into pycnometer. Then measure and record weight of picometer+sample (W pm )
4. Calculate weight of tested sample (A = W
1. Pycnometer 500 mL
b. Testing Procedure
6. Roll, invert, and agitate pycnometer to eliminate all air bubbles.
7. Fill again pycnometer with additional kerosene until volume capacity marking of pycnometer and then measure weigh of picometer + sample materials + kerosene and record the weight (B).
8. Material sample and kerosene are removed from pycnometer and pycnometer is cleaned with kerosene for next steps
9. Fill the empty pycometer with kerosene until volume capacity marking of pycnometer and then measure weight of pycometer + kerosene and record the weight (C).
10. Calculate value of specific gravity by using equation in poin c.
Value of specific gravity for each fine materials are calculated based on following formula:
5. Fill pycnometer partially with kerosene, approximately 90% of the volume capacity of pycnometer.
……..……….. [ 3 ]
Where: Gs : Spesific gravity (no unit)
A : Weight of sample = W - W (grm) B : Weight of Picno + sample + kerosene (grm) C : Weight of Picno+ Kerosene (grm)
: Density of oil (0.83 grm/cm )
: Density of water (1 grm/cm )
3.3.2. Method to Determine Density
This method is conducted according to ASTM C29. This method is conducted to determine dry density of each materials which is used in this research, that’s OPC, bentonite, and BFS. Density of fine material is defined as the ratio of its particle weight to volume of measure.
Weight of particles consist of 3 methods, include rodding, jigging, and shoveling procedure.
1. Balance with precision 5 gram
2. Tamping rod made from steel with diameter and length are 15 mm and 610 mm respectively.
3. Measure is cylindrical which is made from steel and water impermeable.
b. Testing Procedure
1. Dry the sample of materials in an oven until get constant mass
Calibration of measure
2. Fill the measure with water and cover with a piece of plate glass.
3. Determine the mass of the water.
4. Measure the temperature of the water to find its density
5. Calculate the factor for the measure
6. Fill the measure one – third full and leveling the surface with finger.
7. Rod the layer 25 stroke with tamping rod without striking the bottom of the measure.
8. Fill the measure two–third full and leveling the surface as before with the finger
9. Rodd the layer again as before, just penetrating previous layer.
10. Fill the measure to overflowing
11. Rodd the layer again as before, just penetrating previous layer.
12. Level the surface with finger or tamping rod.
13. Determine the mass of the measure and sample content (A), and the measure alone (B), and then record to nearest 0.05 Kg.
14. Calculate value of unit weight using equation in poin c and the calibration factor
5. Fill the measure one – third full and leveling the surface with finger.
6. Raise the measure 50 mm and drop the measure on firm base 50 time (25 time on each side).
7. Fill the measure two – third full and level again the surface as before.
8. Raise and drop again 50 time as before.
9. Fill the measure to overflowing.
10. Raise and drop again 50 time as before.
11. Level the surface with finger or tamping rod.
12. Determine the mass of the measure and sample content (A), and the measure alone (B), and then record to nearest 5 gram.
13. Calculate value of unit weight using equation in poin c and the calibration factor
6 Fill the measure to overflowing by means of shovel or scoop discharging the materials samples from a height not exceed 50 mm above the top of measure.
7 Level the surface with finger or tamping rod.
8 Determine the mass of the measure and sample content (A), and the measure alone (B), and then record to nearest 5 gram
9 Calculate value of unit weight using equation in poin c and the calibration factor
Value of density for each fine materials are calculated based on average of density gotten from 3 procedure include rodding, jigging and shoveling procedure. Density for each procedure is calculated base on following formula:
………..……….. [ 4 ]
3 D : Density (grm/cm )
A : Weight of measure + samples (grm) (Rodding, Jingging, Shoveling procedure) B : Weight of measure (grm)
3 V : Volume of measure (cm )
3.3.3. Method to determine SAI
This method is conducted according to ASTM 593
- 95. This method is conducted to determine strength activity index (SAI) of each material. Strenght acitivity index of material is defined as ratio between compressive strength of mortar mixtures and mortar using OPC as reference mixture. All mortar mixtures must be cured by
o using steam curing on 38±2 C for 7 days.
1. Balance with precision 0.1 gram
2. Measure glass
4. Tamping rod
5. Mortar cylinder mold with dimater and height are 5 cm and 10 cm respectively.
b. Testing Procedure
Prepare and weigh raw material for 3 cylinder 1. specimens (5 cm in diameter and 10 cm in height), with following proportion :
Table 3. 1. Mix proportion for SAI test Raw Material Percentage
Hydrated lime Ca(OH)
Testing sample material 24% Graded standard sand 72%
Determine saturated water content for Hydrated 2.
lime Ca(OH) and testing material according to
ASTM D 1557–02 by using following equation : ……….. [ 5 ]
w : Total saturated water cotent (%)
w : Density of water, 1 gram/cm
: Dry density of sample (gram/cm ) Gs : Spesific gravity of sample Weigh water according to saturated water content 3. of each testing material and hydrated lime material.
Mix testing material, hydrated lime, and 4. saturated surface dry sand until the mixture is uniform in color and texture.
Add water to the mixtures gradually until the 5. mixtures are homogeny, saturated condition and uniform colour.
After saturated mixtures are gotten, cast the 6. specimens immediately in accordance with Method C of Test Methods D 1557. Each layer should be scarified to a depth of 6 mm before the next layer is compacted in order to assure a good bond between the layers.
After specimen mold is full, surface of cylinder 7. specimen should be levelled using tamping rod. Remove specimen from the molding carefully, 8. because the mixture belong to dry mixture. After removing specimens, mortar specimens are 9. put on flat surface. Mortar specimens are cured by using steam 10.
o curing machine on 38 ± 2 C for 7 days.
After 7 days steam curing periods, mortar 11. specimen are removed and weighed. Then mortar specimens are submerged into the 12. water for 4 hour, and then dried for 1 hours. Mortar specimens are capped and subjected to 13. the compresif strength test based on ASTM C 39.
Value of specific gravity for each fine material is calculated based on following equation:
…………..…….. [ 6 ]
Where: SAI : Strengt activity index P : Applied load A : Surface area of specimens
3.3.4. Flow Table Test
This test is conducted to determine water/binder for each series to get same value of consistency (flowability). This test is conducted according to ASTM C 1437 – 07.
a. Apparatus 1.
Flow Table, Flow Mold,
4. Trowel, having a steel blade 100 to 150 mm (4 to 6 in.) in length, with straight edges.
5. Straightedge, made of steel, shall be at least 200
mm in lenght and not less than 1.5 mm nor more than 3.5 mm in thickness.
b. Testing Procedure
1. Clean and dry flow table carefully, and then place the flow mold at the center of flow table.
2. Place a layer of mortar about 25 mm (1 in.) in thickness in the mold and tamp 20 times with the tamper. The tamping pressure shall be just sufficient to ensure uniform filling of the mold.
3. Then fill the mold with mortar and tamp as specified for the first layer.
4. Cut off the mortar to a plane surface flush with the top of the mold by drawing the straightedge or the edge of the trowel with a sawing motion across the top of the mold.
5. Wipe, clean and dry the table top, and remove carefully any water from around the edge of the flow mold.
6. Lift the mold away from the mortar 1 min after completing the casting operation.
7. Immediately drop the table 25 times in 15 s, unless otherwise specified
8. Mesure the diamater of the cement paste above flow table, and record the result.
2 Figure 3. 2. Measuring flow diamater of cement paste
The flow is defined as average of minimum 2 diamater from different point measurement of diameter. The flow is calculated based on following equation :
......…………..……... [ 7 ]
Where : Flow : Floability of cement paste (mm) d i : Diameter of cement paste measurement i (mm) n : Number of diameter measurement
3.3.5. Particles Size Analyze
Particle Size Analyze (PSA) is used to determine particle size and particles distribution for OPC, bentonite, and blast furnace slag (BFS). Distribution of particle is means the percentage amount of particle for each particles size. This PSA result is compared to reactivity data and healing effectiveness. This PSA test is conducted in Cement Research Center (PPS), PT. Semen Indonesia, Tbk. Method to determine particle size and its distribution are describe as follow:
1. Malvern instrument for PSD analysis
3. Specimen chamber
b. Testing Procedure
1. Introduce material sample to specimen chamber by using spatula.
2. Put specimen chamber containg material sample to the Malvern instrument.
3. Choose material reference in Malvern software for each material.
4. Run sample until process finish.
5. Remove sample from the Malvern instrument and from chambers.
Data from this testing are distribution of each particle size that is shown by distribution particle curve. This curve consist of particles size in x axis and percentage particles in Y axis.
3.3.6. X-Ray Fluoroscene
X – Ray Fluoroscene is used to determine chemical element and its percentage of raw materials such as OPC, bentonite, and Blast furnace slag. This chemical element data is very important to analyze material properties, determine mineralogy in XRD analysis and analyze self healing properties of cement paste made from this materials.
3.3.7. X-Ray Diffraction
X – Ray Diffraction is used to determine mineral compound and its percentage of raw materials such as OPC, bentonite, and Blast furnace slag. This chmineral compound data is very important to analyze material properties and self healing properties of cement paste made
3.4. Mix Proportion Series
To characterize and quantify the self healing ability of cement paste, four series are set up: (1) OPC (2) OPC incorporating BFS (3) OPC incorporating bentonite; and (4) OPC incorporating BFS and Bentonite. Detail composition for each series are shown in Tabel 3.2. This four series are set up to analyze influence of bentonite, blast furnace slag, and combination both of them to the self healing ability of cement paste, and compare to normal cement paste (B0S0).
Figure 3. 3. Explanation of Sample Code Table 3. 2. Mixture composition for each cement paste series Series % OPC % BFS % BNT w/c*
- B0S0 100 % A - B5S0 95 % 5 % B - B0S30 70 % 30 % C B5S30 65 % 30 % 5 % D *the value of w/c for each series (A, B, C, D) is gottem from flow table test
3.5. Specimens Series
For each series, 3 kinds of specimens are employed, dogbone/briquet specimen is analysed for direct tensile regain and visual crack closure, cracked prisms 10 cm x 10 cm x 40 cm is used to quantify visual crack closure, depth of crack, and flexural regain, and cylinder specimens with
3.5.1. Dogbone/Briquet Specimen
Dogbone/briquet specimens are carried out to determine direct tensile regain after crack. Detail specification of dogbone specimens are shown in Figure 3.4 bellow.
Figure 3. 4. Detail specification of briquet
Source: CRD-C 260-01
3.5.2. Beam 10 x 10 x 40
Beam 10 x10 x 40 specimen is carried out to determine crack closure rate, crack depth, and flexural regain. Detail specification of beam specimens dimension are shown in Figure 3.5. Beams were given crack initiation 5 mm to make sure that crack will be occurred in the certain poin ( Figure 3.6). This beams were holded by steel renforcement to control crack width. Steel reinforcement were designed by considering ultrasonic pulse velocity (UPV) testing and measurement. Detail specification of steel reinforcement is shown in Figure 3.7.
Crack initiation by introducing 10 cm teflon sheet as depth as 5 mm
40 cmFigure 3. 5. Dimension of Beam specimens
Crack initiation by introducing Beam Teflon sheet as depth as 5 mm Specimens
15 cm 10 cm 15 cm
Figure 3. 6. Crack initiation by indtroducing teflon sheet
as depth as 5 mm
3.5.3. Cylinder Specimens
Cylinder specimens with diameter 10 cm and thickness 8 cm were carried out to determine cloride penetration. Detail specification of specimens are shown in Figure 3.8. Before permeability testing, cyliner specimen were subjected to splitting test to introduce artificial crack. During splitting test, cylinder specimens were confined by using duct tape to control crack width. Then cracked cylinder specimens were coated by using waterprof on cover side of cylinder specimens. Coated specimens were shown in Fig.3.9.(a). Then, specimens were put in pipe and put waterprof on top and bottom of cylinder specimen only put on circumference line of cylinder specimen ( see Fig. 3.9.(b) ).
8 cm 10 cm Figure 3. 8. Cylinder specimens artificial crack a b Figure 3. 9. Coated specimens, a) cover side b) top side
3.6. Specimens Casting
Specimen used in this research is cement paste incoporating some material such as bentonite and BFS as partial cement replacement. Procedure for specimen casting is described as follow:
2. Molds for 3 specimens (Briquet, beam, and cylinder)
3. Steel reinforcement
4. Leveling apparatus (ex : Rule)
5. Rubber hammer
6. Balance with precision 1 gram
1. Mixer machine
4. Introduce OPC, bentonite, and BFS into mixer chamber, and mix material with low speed for 2 minutes until the mixture has same colour.
5. Stop mixer machine and then introduce some water (don’t introduce the all of water) to the mixtures, and then mix again with low speed for 2 minutes until the mixtures homogen.
6. Stop mixer machine and introduce additional water to the mixtures, and then mix again with middle speed for 4 minutes until the mixtures homogen.
7. Remove mixtures from the mixer machine, and then fill paste mixtures into the mold one – third full and compact specimen with hammer.
3. Measure weight all of materials (OPC, bentonite, BFS, and water) based on mixture proportion for each series in sub chapter 3.4.
1. Prepare molding for 3 kinds of specimen (Briquet, Beam 10 x 10 x 40, and cylinder 10 cm in diameter and 8 cm in thickness) and reinforcement for beam 10 x 10 x 40.
2. Introduce oil inside of molding suface in order the specimen can be removed easily from the mold.
8. Fill again the mixtures into the mold two – third full, and compact specimen with rubber hammer.
9. Fill again the cement mixtures into the mold until overflowing, and then compact specimen with rubber hammer.
10. Level the specimen surface with ruller.
11. Introduce mica (ticknes 0.1 mm) to the beam specimens as depth as 5 mm to initiate artificial crack occure in that point.
12. Remove specimens from the mold after 24 hour after casting process.
13. And then cure specimen into wet curing condition
3.7. Curing Condition
All of the specimens were cured in wet curing condition until introducing artificial crack. Wet curing was conditioned by wraping all specimen by using wet burlap. Then the wet burlap was maintenanced always on the wet condition. 1 day before introducing artificial crack on 28 age days after casting, specimens were removed from wet curing condition, and then dried by using air condition.
Figure 3. 10. Curing by covering specimens with wet burlap
3.8. Introducing Artificial Crack
Artificial cracks were created by using 3 methods based on type of specimens. Dogbone/briquet specimens were subjected to direct tensile test until specimen separate become two part, and then two part were connected become 1 part specimen and then 1 part specimen was holded by using dogbone specimen holder. Prisms 10 cm x 10 cm x 40 cm specimens were subjected to four point bending test until crack occur. Cylinder specimens were subjected to splitting test until the crack occur. Cracked width of all specimens are controlled under 0.3 mm that is maximum cracks width permitted by ACI 224R-01.
b a Figure 3. 11. Introducing artificial crack, a) Cylinder
specimens by using splitting test, b) beam specimens by using four point bending test
ba Figure 3. 12. a ) Introducing artificial crack of dogbone
specimens by using tensile test, b) dogbone specimens are
3.9. Water Imersion Curing
After all of specimens have been cracked, then the all of specimens are cured again by immersing specimens in water. 1 day before observation and measurement on 7, 14, 28, and 56 age days after introducing artificial crack, specimen are removed from wet curing process, and then dry using air condition.
Figure 3. 13. Water Imersion Curing
3.10. Self Healing Evaluation
Five kinds of testing and measurement are carried out to evaluate self healing behavior of the cement paste specimens, including ultrasonic pulse velocity testing, microscopic investigation, direst tensile testing, and flexural testing. That testing and measurement are explained as below:
3.10.1. Ultrasonic Pulse Velocity Testing
Ultrasnic pulse velocity is carried out to evaluate self healing process of specimens, in term of crack depth changes on 0, 7, 14, 28, and 56 days after cracking. This method is conducted according to
ASTM C597 – 02.
The testing apparatus is shown schematically inFigure 3.14 , consists of a pulse generator, a pair
of transducers (transmitting transducer and receiving transducer), a receiver amplifier, a time measuring circuit, a time display unit, and connecting cables. Beside that, cracked beam is prepared for this testing and measurement.
Figure 3. 14. Schematic of Pulse Velocity Apparatus
Source: ASTM C597 – 02
b. Testing Procedure
1. Verify that the UPV equipment is operating properly and perform a zero-time adjustment.
Perfome a zero time adjustment using Automatic Zero-Time Adjustment by Apply coupling agent to the transducer faces and press the faces together.
2. Check the zero adjustment on an hourly basis
during continuous operation of the instrument, and every time a transducer or connecting cable is changed. If zero-time adjustment cannot be accomplished, do not
3. Determine measurement poin on the testing
specimens. First measurement poin is measured 5 cm from crack line position, both for transmitter poin in the right side of crack line position and receiver poin in the left side of crack line position.
4. Apply an appropriate coupling agent (in this
case gell is used as coupling agent) to the transmitter faces and receiver face or the specimen surface, or both. Press the faces of the transducers (transmitter and receiver) firmly against the surfaces of the specimen until a stable transit time is displayed, and
1 measuring the transit time (t ).
5. Conduct second measurement in the second
measurement poin. Second measurement poin is measured 10 cm from crack line position, both for transmitter poin in the right side of crack line position and receiver poin in the left side of crack line position.
6. Conduct same procedure in step 4 and then
2 measuring the transit time (t ) x x 2x 2x
T R T R T Figure 3. 15. Transmitter and receiver position for
Figure 3. 16. Typical arrangement for Measuring
Crack depth are calculated based on the following equation: Where: h : crack depth x : distance of transmitter or receiver to crack line on first measurement poin t
: transmitting time of ultrasonic pulse of first measurement point t
2 : transmitting time of ultrasonic pulse of
second measurement point
This microscopic inverstigation was conducted by utilizing Dinocapture 2.0 digital camera with maximum magnification scale is 900x. Observation was carried out using 250 time magnification scale. This method is used to investigate self healing process in term of decreasing crack width. The self-healing process is shown by healing efficiency index from 15
….…………..…….. [ 8 ]
3.10.2. Microscopic Investigation
measurements were perfomed after 0, 3, 7, 28, 56 days after introducing artificial crack. The methods to determine healing efficiency index are described as follow:
1. Dino capture 2.0 instrument
2. Water resisten ballpoin/spidol
b. Investigation Procedure
1. After artificial crack is created in specimen, then crack line is signed for 15 measurement point by water resisten ballpoin to make constant investigation and measurement point.
2. Dinocapture are set up, both camera instrument, camera holder, and dinocapture software in computer.
3. Specimens are put under of camera, and make sure that surface of specimen for investigation is clean and in dry condition.
4. Set up focus of camera to get the best picture from specimen.
5. Set up magnification scale on the both in the camera and in the software
6. Measure crack width for investigation poin 1, and continue to the other investigation point until investigation poin 15.
7. Record data of crack width for 15 investigation poin.
8. Calculate healing efficiency index
Value of healing efficiency index is calculated based on following formula:
….…………..…….. [ 9 ] Where: : Healing efficiency index
A : The area covered by initial crack width (The area under L(0) line) A
: The area covered by crack width after ceratain healing time (The area under L(T) line)
: The difference in area between these two as highlighted by diagonal line shown in figure 3.8
Figure 3. 17. Example crack width graphic
for calculating healing efficiency index
d. Measuring crack width
1. Determine crack position
2. Choose line menu in Dinolight software
Figure 3. 19. Choosing line button
3. Measure crack width by drawing minimum 10 line in the crack point.
Figure 3. 20. Drawin line
4. Show the crack width result of 10measurement by using measurement properties button. Then the result is exported to excel.
5. Crack width of one observation point is average from 10 measurement of crack width result as shown in Fig. 3.21.
e. Measuring Crack Area
1. Determine crack position
Figure 3. 22 Determine crack position
2. Draw poligon line in the certain crack point by using poligon menu button in dinolight software
Figure 3. 23. Drawing poligon line
3. The value of crack area is shown in the red rectangular line in Fig.3.23
Measurement point of crack area Value of crack area
3.10.3. Four Point Bending Test
This test is conducted to determine the self healing properties of each series in term of flexural strength regain. This test is conducted according to ASTM C 1608. Apparatus and testing procedure is described as follow:
1. Universal Testing Machin
2. Beam support system
Steel rodd 3.
4. Steel Plate
5. Data Recording System
1. Remove specimen from curing process, and dry specimen before the specimen is subjected to four point bending test.
2. Arrange the specimen and the loading system so that the specimen is loaded at the four points in accordance with Test Method C78.
3. Operate the testing machine so that the net deflection of the specimen increases at a constant rate in accordance with Table 3.3.
Table 3. 3. Rate of Increase in Net Deflection Beam Size Up to net Beyond net deflection of deflection of L/900 L/900
100 by 100 0.025 to 0.075 0.05 – 0.20 by 350 mm mm/min mm/min 150 by 150 0.035 tp 0.10 0.05 to 0.30 by 500 mm mm/min mm/min
4. Apply load until the beam specimen reach first crack for introducing artificial crack and Apply load until the beam specimen reach failure condition for healing evaluation.
Figure 3. 24. Typical arrangement for Four Point
1. Values of load and deflection used in subsequent calculations shall be obtained from the load-deflection curve, or from stored digital data. and the flexural strength is calculated based on following formula :
………….………..…….. [ 10 ] Where: f : the strength, MPa
P : the load, N L : the span length, mm b : width of the specimen, mm and d : depth of the specimen, mm.
5.10.4. Direct Tensile Strenght Test
This test is conducted to determine direct tensile regain of the cement paste after healing time. This test is conducted according to CRD-C 260-01. Test procedure is described as follow:
1. Direct tensile testing machine
b. Testing Procedure
1. Wipe briquette specimen to a surface-dry condition, and remove any loose sand grains from the surfaces that will be in contact with the clips of the testing machine.
2. The bearing surfaces of the clips shall be clean and free of sand, and the roller bearings shall be well oiled and maintained so as to ensure freedom of turning.
3. Keep the stirrups supporting the clip free of accumulations, and keep the pivots in proper adjustment so that the clips may swing freely on the pivots without binding in the stirrups.
4. Instroduce carefully the briquets in the clips and apply the load continuously at the rate of 600 ± 25 lbf (2.67 ± 0.11 kN) /min.
Figure 3. 25. Typical arrangement for direct
tensile test according to CRD-C 260-01
5. Record the total maximum load indicated by the testing machine and calculates the tensile strength in kilopascals.
6. The tensile strength of all acceptable test brique:ts made from the same sample and tested at the same period shall be averaged
The tensile strength is calculated based on following equation:
………..………..…….. [ 11 ]
T : Direct tensile strength, Kpa
P : Total maximum load, kN
2 A : Cross sectional area, m
If the cross-sectional area of a briquet varies more than 2.0 % from the nominal, use the actual area for the calculation of the tensile strength.
5.10.5. Measuring pH of Specimens
This test is conducted to analyze self healing process which occur for each mixtures. Ph measurement was conducted for four mixtures, include inside specimens and inside cracks. Method to determine ph is described as follow:
a. Apparatus 1. Digital balance with 0.1% in precision.
2. Baker glass with 50 mL in volume capacity 3. pH meter
4. Mechnical stirrer
5. Porselin cup
1. Free ion water
2. Buffer solution with pH 7.0 and 4.0
3. Cement paste specimens
c. Testing Procedure
It is not recomended to use buffer 10 due to poor stability as a result buffer reaction with CO2 from atmosphere.
5. Submerse the electrode into cement paste suspension. Note that the cement paste
4. Prepare calibrated pH meter.
3. Stir the suspension for 30 minutes by using mechanical stirrer.
2. Make cement paste suspension by dissolving 100 gram cement paste powder with 500 mL free water ion (ratio between the powder and water are 1 : 5)
1. Grind cement paste using porseline cup
9. Wait until the pH icon stops flashing and press the calibrate button. 10. pH meter is ready to use
Calibration procedure 1. Turn on pH meter.
2. Waite arround 30 minutes for the pH meter to warm up.
7. Rise the electrode with distilled water and wipe with Kimwipe.
6. Wait until the pH icon stops flashing and press the calibrate button again.
5. Press the calibrate button.
Note that buffers and sample should be read at room temperature.
4. Submerse the electrode into pH 7 buffer.
Do not wipe the electrode membran, but instead dab the electrode with Kimwipe.
3. Rinse the electrode with distilled water.
8. Submerse the electrode into pH 4 buffer. suspension and buffer solution should be read at room temperature.
6. Press the measure button.
7. Wait until the pH icon stops flashing and record the pH of ceement paste.
5.10.6. Cloride Ion Penetration Test
Cloride ion penetration test was conducted to determine durability of cracked specimens after healing process. Cracked specimens were coated by using impermeable agent (aquaproof) on cover side of cylinder specimens. Then, specimens were put in pipe and waterprof was introduced on the bottom side of cylinder specimens. This test was conducted in Laboratorium TAKI, chemical engineering departement ITS
Healed Crack b c a
Figure 3. 26. a) Cylinder Specimens for cloride
penetration, b) Top Side, c) bottom side Cracked specimens which had been healed perfectly, were submerged in solution with NaCl concentration 5% for 3 days. This solution was made by dissolving water and NaCl. 5 gram NaCl flake were dissolved in 1 L water.
a b Figure 3. 27 . a) NaCl Flake, b) Dissolving NaCl flake
in the water
a b Figure 3. 28 . a) Solution for Cloride penetration,
b) Specimens were submerged in NaCl solution
After submersion process, specimens were removed, then specimens were splitted become two part. To determine cloride penetration of each specimens, 4 location were choosen for cloride ion penetration test. 4 location were choosen 2 cm, 4 cm, and 6 cm from top side for crack area, and 4 cm from top side for non crack area. Sampling for cloride ion penetration specimens were visualised
- - NaCl Na
2 cm 4 cm Cylinder Specimens
6 cm 8 cm Figure 3. 29. . Sampling for Cloride Ion Penetration
5.10.7. XRD Analysis
This XRD analysis is used to verivy the healing mechanism occurred in the specimen by identify mineral closing crack gap. Beside that from this method, the dominant effect of self healing mechanism in cracked cement paste can be analyzed. This test is conducted on 56 gae days after cracking or after crack almost closed completely.
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CHAPTER IV RESULTS AND DISCUSSIONS
4.1. General Introduction In this chapter, it will be described about testing and observation result, both for raw materials used in this research and cement paste, especially for healing properties of the cement paste. Generally, testing and observation result are decided into two parts, including a testing result of raw materials, and self healing evaluation. Testing results of raw material are specific gravity, dry density, strength activity index, XRD, XRF, particle size and also flow ability of the cement paste mixtures. Self healing evaluation include some parameters, such as crack width, crack depth, direct tensile regains and flexural regains of some cement paste mixtures.
4.2. Testing Result of The Raw Materials Some testing of raw material, such as specific gravity, density, SAI, XRD, XRF, particle size, and flow ability were conducted to support self-healing property's data of the cement paste. Some materials tested in this research are bentonite, blast furnace slag, and cement paste mixtures.
4.2.1. Spesific Gravity of Material
Table 4. 1. Specific Gravity Test Result of OPC Weight Value Trial Unit
2 Weight of Pycno + Kerosene (C) gram 554.20 554.15 Weight of Pycno + Kerosene + Sample (B) gram 652.90 652.80 Weight of pycnometer + sample (W ) gram 274.50 274.20 pm
Weight of pycnometer (W ) gram 140.50 140.30 p
Weight of sample (A=W –W ) gram 134.00 133.90 pm p
3.14 - Specific Gravity
3.14 Specific Gravity average -
Based on the testing result in Table 4.1, Portland cement,
which is used in this research has specific gravity 3.14.
According to ASTM C-188-89, specific gravity of the
ordinary Portland cement is varied between 3.05 – 3.25.
Thus, cement Portland used in this research still complieswith requirements in ASTM C – 188 -89.
Table 4. 2. Spesific Gravity Test Result of Ca-Bentonite
Trial UnitWeight Value
2 Weight of Pycno + Kerosene (C) gram 556.20 616.00
Weight of Pycno + Kerosene + Sample (B) gram 648.00 692.00
Weight of pycnometer + sample (W pm ) gram 276.30 243.80Weight of pycnometer (W p ) gram 141.00 118.90
Weight of sample (A=W pm – Wp ) gram 135.30 124.50Specific Gravity
2.55 Specific Gravity average - 2,57 Based on testing results in Table 4.2, Bentonite
used in this research has specific gravity 2.78. This result is
also similar to the specific gravity conducted by other
researchers such as Sree et al (2011) with specific gravity
of bentonite is 2.60. Besides that, based on Soedjoko TS
(1987), specific gravity of bentonite is varied between 2.40
– 2.80. Thus, specific gravity of BFS used in this researchcan be accepted.
Table 4. 3. Spesific Gravity Test Result of BFS
Trial UnitWeight Value
2 Weight of Pycno + Kerosene (C) gram 524.50 562.50
Weight of Pycno + Kerosene + Sample (B) gram 619.00 651.00
Weight of pycno + sample (W pm ) gram 243.00 274.20
Weight of pycno (W p ) gram 110.50 149.70
Weight of sample (A=W pm – Wp ) gram 132.50 124.50Specific Gravity
2.77 Specific Gravity average -
2.78 Based on testing results in Table 4.3, Blast Furnace Slag used in this research has specific gravity 2.78. This result is also similar to the specific gravity conducted by other researchers such as Yim et al (2015) with specific gravity 2.95, Asad et al (2013) with specific gravity 2.87 for China BFS, 2.75 for Pakistani BFS, and 2.76 for India BFS, Jariyathitipong et al(2015) with specific gravity of BFS is 2.74, Hirde and Pravin (2015) with specific gravity of BFS is 2.87. According to Australian (Iron and steel) Association (2011), specific gravity of blast furnace slag is varied between 2.75 – 2.85. Thus, specific gravity of BFS used in this research can be accepted.
Generally, ordinary Portland cement has higher specific gravity followed by blast furnace slag and bentonite. However, specific gravity of ordinary Portland cement is
almost similar to specific gravity of Blast Furnace Slag.
4.2.2. Density of Material
Dry density of the material is used to calculate the amount of water needed for reactivity specimen for each material. The density test results of OPC, bentonite and BFS are
shown in Tabel 4.4, Table 4.5, Table 4.6 respectively.
Table 4. 4.
Density Test Result of OPC Weight for each procedures Trial Unit Rodding Jigging Shoveling
2 W chamber (B) gr 1.07 1.07 1.07 1.07 1.07 1.07 chamber and sample W (A) gr 3.63 3.60 3.56 3.56 3.30 3.30 W sample (A – B) gr 2.57 2.54 2.49 2.49 2.24 2.23 3 V chamber (V) cm 2.00 2.00 2.00 2.00 2.00 2.00 Dry density for each
3gr/cm 1.28 1.27 1.25 1.24 1.12 1.12 procedure ([A-B]/V) Dry density for each
3Dry density gr/cm
1.21 Based on testing result in Table 4.4, OPC used in this research has dry density 1.21 gr/cm 3 .
Table 4. 5. Density Test Result of Ca – Bentonite Trial Unit Weight for each procedures Rodding Jigging Shoveling
0.94 Based on testing result in Table 4.6, Blast Furnace Slag used in this research has dry density 0.94 gr/cm
0.84 Dry density gr/cm 3
2 W chamber (B) gram 1.07 1.07 1.07 1.07 1.07 1.07 W chamber and sample (A) gram 3.08 3.05 3.00 3.00 2.76 2,72
W sample (A – B) gram 2.02 1.98 1,94 1.94 1.69 1.66V chamber (V) cm 3 2.00 2.00 2.00 2.00 2.00 2.00 Dry density for each procedure([A-B]/V) gr/cm 3 1.01 0.99 0.97 0.97 0.85 0.83 Dry density for each procedure gr/cm 3
Table 4. 6. Density Test Result of BFS Trial Unit Weight for each procedures Rodding Jigging Shoveling
0.87 Based on testing result in Table 4.5, Bentonite used in this research has dry density 0.87 gr/cm
0.79 Dry density gr/cm 3
2 W chamber (B) gram 1.07 1.07 1.07 1.07 1.07 1.07
W chamber and sample (A) gram 2.93 2.93 2.82 2.81 2.63 2.67
W sample (A – B) gram 1.86 1.87 1.75 1.75 1.56 1.60V chamber (V) cm 3 2.00 2.00 2.00 2.00 2.00 2.00 Dry density for each procedure ([A-B]/V) gr/cm 3 0.93 0.93 0.88 0.87 0.78 0.80 Dry density for each procedure gr/cm 3
4.2.3. Strenght Activity Index
Strenght activity index test is carried out to determine reactivity of the raw material by using lime Ca(OH) 2 . Mortar specimens were used for this testing. The mortar were made from testing sample, graded sand, Ca(OH) 2 with precentage 24%, 4%, and 72% respectively, as purpose in ASTM 593 – 95. The sand must be in saturated dry condition. Because the testing sample and Ca(OH)
2 were in dry condition, saturated water content must be determined firsly to get dry mortar mixture. The saturated water content for each materials are shown inTable 4.7. The composition for each mixtures are shown in Table 4.8.
Table 4. 7. Saturated water content for each raw material Parameter Ca Bentonite Ca(OH) w ) 2 OPC BFS
1.00 Density of water ( Spesific gravity (Gs)
0.94 Dry density d W (%) sat
76.66 23.52 50.68 70.96
Table 4. 8. Mixture compostion for each raw materialWeight of material, G (gram)
Sample Ca(OH)2 Sand Water* sample
(24%) (4%) (72%) (W w ) Bentonite Ca 311.02 51.84 933.05 250.61 OPC 311.02
51.84 933.05 169.82 BFS 311.02 51.84 933.05 232.88 Ca(OH)2
*Ww = W sat sample (%) x G sample + W sat Ca(OH)2 (%) x G
Mortar specimens for each raw material were cured o
by using steam curing machine on 38 ± 2 C for 7 days.
After 7 days steam curing periods, mortar specimens were
removed from curing machine and submerged into the
water for 4 hour. Then, mortar specimens were dried for 1
hours and subjected to the compresif strength test based on
ASTM C 39. The compressive strength result of mortar
specimens are shown in Table 4.9. The strength activity
index is defined as a ratio between compressive strength of
mortar mixtures (OPC, bentonite, and BF) and mortar
using OPC as reference mixture. The SAI of each materialsare shown in Table 4.9, and then drawn in Figure 4.1.
Table 4. 9. SAI Test Result of Some Raw Materials
Material SAI CovFc on 7 age days (Mpa) Average (Mpa)
3OPC 22.92 25.47 23.43 23.94 1.00 1.55 % Bentonite 3.85
3.743.78 0.16 1.59 % BFS 17.83 17.83 16.81 17.49 0.73 3.36 % Average compressive strength of three specimens i.e
OPC, Ca Bentonite, and BFS are 23.94 Mpa, 3.78 Mpa,
17.49 Mpa respectively. Coefficient of varians from 3 SAI
testing of OPC, Ca Bentonite, and BFS are 1.55%, 1.59%,
and 3.36 % respectively. According to SNI 03 – 6815 –
2002, varians coefficient of testing in the laboratory is
classified into five parts, that are excellent, very good,
good, enough, less with the varians coefficients in range of
0 – 3.0, 2.0 – 3.0, 3.0 – 4.0, 4.0 – 5.0, and greater than 5.0
respectively. Thus, SAI testing is classified as excellent
and good, and still comply with requirements in SNI 03 –6815 – 2002.
Figure 4. 1. SAI of OPC, Ca-Bentonite and BFSStrength Activity index of bentonite is 0.15. This
value is smaller than other materials. Although bentonitehas SiO 2 content 73,53 %, but structure of bentonite
belongs to crystalline. This fact is inline with XRD result
in Fig. 4.2. The diffractogram of bentonite show less area
under the graphic and high intensity of peak. This indicates
that bentonite used in this research belong to Cristaline
Mineral. On the other hand, reactivity index of BFS is
0.73. This value is smaller than OPC but greater than Bentonite. This fact is inline with XRD result in Fig. 4.3..
The diffractogram of BFS show wide area under the
graphic and little intensity of peak. This indicates that BFS
used in this research belongs to amorphous mineral. The
strength of BFS isn’t attributed by pozzolanic reaction,when the reactive silica reacts with Ca(OH) 2 to form C-S-
H, but the strength of BFS is mainly attributed by latenthydraulic reaction. Its means that BFS need Ca(OH) 2 to
activate its particle to form hydration reaction. This latent
hydraulic reaction is slower than normal hydration in OPC.
Thus, the SAI of BFS less then SAI of OPC.
According to ASTM C989-05, slag is classified
into three grades based on its SAI value, that are Grade 80,
Grade 100 and grade 120 with a minimum limits of SAI at
7 days are 0%, 70%, and 90% respectively. Because SAI
of slag is 73%, thus blas furnace slag used in this research
The XRD result of BFS is reported on Diffractogram in Fig. 4.2, and Table 4.10. Based on diffractogram in Fig. 4.2, there is little peak shown in diffractogram of BFS. Beside that, The area under graph is very wide. This two parameter show that BFS used in this research belong to amorphous mineral. The amorphous mineral almost has hight reactivity. Only little peak shown in Fig 4.2, such as peak of Quartz mineral (peak a) and peak of calcite mineral (peak b). This two mineral (quartz and calcite) belong to cristaline mineral.
The complete quatitative and qualitative analysis result of diffractogram of BFS are shown in Table 4.8. Almost 97,26 % of BFS contains amorphous mineral (shown by hkl_phase). Only almost 2.75 % of BFS contains cristaline mineral, that are Quartz and calcite. Thus, BFS used in this research is almost reactive.
Table 4. 10. No Kode Cristaline Formula Percentage Unit Mineral Compound of BFS SiO 2 1 a Quartz 2,44 % CaCO 3 2 b Calcite 0,31 % Amorphous
97,26 - -% mineral The XRD result of Ca - Bentonite is presented on Diffractogram in Fig. 4.3, and Table 4.11. Based on diffractogram in Fig. 4.3, almost of diffractogram show hight number of peak, and less area under the graphic. This two parameter show that BFS used in this research belong to cristaline mineral. The christaline mineral almost has low reactivity. Some peak such as peak q, peak m and peak t showed Quartz , Montmorilonite and Tridymite mineral respectively.
Table 4. 11.
Mineral Compound of Ca – Bentonite
No Kode Cristaline Formula Percentage Unit
- hkl_Phase %
2 q Quartz 73,53 %3 m Montmorillonite Ca
0.5 (Al2 Si 4 O 11 (OH)) 9,21 %
4 t Tridymite 13,01 %
The complete quatitative and qualitative analysis
result of diffractogram of Ca - bentonite is shown in Table
4.11. Ca-Bentonite used in this research contains Quartz,
Montmorillonite, and Tridymite. Precentage of Quartz,
Montmorillonite, and Tridymite are 73,53 %, 9.21 %, and
13,01 % respectively. Although almost 86,54 % Bentonitecontain SiO
2 , this mineral doesn’t reactive. But there is
Montmorilonite mineral which produce swelling properties
in bentonite. The percentage of Montmorillonite influencesthe swelling capacity of bentonite.
According to Puslitbang Tekmira (2005), bentonite
generally is divided in two part, including Ca Bentonite
and Na Bentonite. The differences are taken place on its
swelling properties. Na-Bentonite has hight swelling
capacity. It is mainly caused by hight amount of
Montmorilonite mineral. Since the Montmorillonite
content in bentonite increase, it will be followed by
incrrease in swelling capacity of bentonite. Because of that
Kishi et al (2009) using bentonite which has hight swelling
capacity. The bentonite whic is used containMontmorillonite Na
7.32 O 20 (OH) 4.
Because of the amount of Montmorillonite in Ca
Bentonite 9,21% (Table 4.11), thus the swelling capacity
is smaller than Na Bentonite used by Kishi (2009) with montmorillonite content almost 76%. a = Quartz b = Calcite Figure 4. 2.
Diffractogram of BFS q = Quartz m = Montmorilonite t = Tridymite
Figure 4. 3. Diffractogram of Bentonite
XRF testing is carried out to indentify chemical element compound of BFS and Bentonite. The results are shown in Table 4.12 and Table 4.13.
Table 4. 12. Chemical Compound of Bentonite
No Parameter Unit Test Result
1 SiO 2 % weight 56,13
2 O 3 % weight 21,57
2 O 3 % weight 5,31
2 O % weight 1,29
5 MgO % weight 0,95
6 TiO 2 % weight 0,87
7 CaO % weight 0,58
2 O % weight 0,23
2 O 3 % weight 0,01
10 MnO2 % weight 0,01
11 Loss on Ignition % weight 0,01 Based on Table 4.12, main oxide compounds in Bentonite are SiO 2 , Al
2 O3 , and Fe
2 O 3 with precentage 56.13% , 21.57% , and 5.31% respectively. Total amount of SiO
2 , Al
2 O 3 , and Fe
2 O3 oxide is 83,01%. Based on 2 , ASTM C 618 – 03, material having total amount of SiO Al
2 O 3 , and Fe
2 O 3 greather than 70%, must be classified as pozzoland material. Basically, bentonite belong to pozzoland material, but it has low reactivity based on SAI testing. To improve reactivity, bentonite should be activated by alkaline solution or burning process. Highest precentage of SiO 2 and Al
2 O 3 oxide are main compound which compose Quartz, Montmorillonite and Tridymite mineral.
Table 4. 13. Chemical Compound of BFS
No Parameter Unit Test Result
1 SiO 2 % weight 36,33
2 CaO % weight 34,59
2 O 3 % weight 16,04
4 MgO % weight 9,24
2 O 3 % weight 0,95
6 MnO2 % weight 0,74
7 S % weight 0,45
2 O % weight 0,46
2 O % weight 0,31
2 O 3 % weight 0,15
11 Loss on Ignition % weight 0,14 Based on Table 4.13, main oxide compounds of BFS are CaO, SiO 2 , Al
2 O3 , Fe
2 O 3 and MgO with
precentage 34,59%, 36.33% , 16.04% , 0.95% , and 9,24 %
respectively. This result is similar to the oxide compound
of cement portland. As comparison, Based on Subakti et al
(2012), the oxide compound of portland cement isdominated by CaO, SiO 2 , Al
2 O 3 , Fe
2 O 3 and MgO with
precentage vaeried between 60% – 66%, 19% – 25%, 3% –
8 % , 1% – 5% , and 4% respectively. Because of that, BFS
also has hydration reaction properties like portland cement.
But, the hydration reaction is slower than portland cementand BFS also need activator to activate its particle.
Beside that, According to ASTM C989-05, the amount of sulfide/sulfur and total alkalies (Na
2 O + 0.658 K
2 O) are limited 2,5% max and (0.60% – 0.90%)
respectively. Based on XRF result in Table 4.8, the amount
of sulfida oxide is 0.45 %. The total amount of total
alkalies oxide in BFS is calculated according to ASTM C989-05 as follow : Total Alkalies = (Na
2 O + 0.658 K
2 O) = 0.31% + 0.658 x (0.46%) = 0.61268 %
The total alkalies value is greather than 0.6% and less than 0.90%. Thus chemical propoerties of BFS still conform
4.2.6. Particles Size Distribution
Particle Size Analyzer (PSA) is carried out to identify partilce size and gradation/distribution of Bentonite and BFS. The result of particle size distribution is shown in Fig 4.4 and Fig 4.5. The result of Cummulative particle size is shown in Fig 4.6 and Fig 4.7.
Figure 4. 4. Particle Size Distribution of Bentonite Based on Fig. 4.4, all bentonite particle which is used in this research pass 400 µm. It means that maximum diameter of the bentonite particle is 400 µm. Higest volume particle is plotted in diameter 2.5 µm, followed by 20 µm, and 150 µm. It indicate that bentonite particle is distributed evenly for each particle size.
Figure 4. 5. Cummulative Particle Size of BentoniteBased on Fig. 4.5, the amount of bentonite particle
passing 75 µm is 81,02 % from the total volume. It means that
almost 18.98% of the bentonite particle belongs to fine
aggregat, because the particle diameter is greather than 75 µm
and smaller than 4,78 mm (maximum diameter is 400 µm).
Bentonite particle used in this research had median particlesize (d50) 8,602 µm.
Figure 4. 6. Particle Size Distribution of BFS Based on Fig. 4.6, all BFS particle which is used in this
research pass 125 µm, it means that maximum diameter of the
BFS particle is 125 µm. The particle size distribution of BFS
(Fig. 4.6) include to normal distribution. Higest volume
Figure 4. 7.
Cummulative Particle Size of BFS Based on Fig. 4.7, the amount of BFS particle passing 75 µm is 92,58% from the total volume. It means that almost 7,42% of the BFS particle belongs to fine aggregat, because the particle diameter is greather than 75 µm and smaller than 4,78 mm (maximum diameter is 125 µm). BFS particle used in this research has median particle size (d50) 27,632 µm.
Based on the PSA result of Bentonite and BFS, the amount of BFS particle passing 75 µm is gretaher than bentonite. But the median diameter particle of Bentonite is smaller than BFS diameter. It is caused by hight percentage of bentonite particle which has diameter smaller than 30 µm.
4.2.7. Spesific Surface Area (SSA)
Blaine test is carried out to determine spesific surface area of the raw material, including bentonite and BFS. Specific surface area is defined as total surface area of particle, which has correalation with reactivity properties As wide as Spesific surface area of powder material, it will be followed by increasing reactivity of the powder material.
Table 4. 14. Spesific Surface Area Properties Average Time T SSA (cm2/gr) SSA Sample Testing 2 ( Sec ) (cm /gr) 60.50 2950.34
2 57.70 2881.26 2933.79 61.30 2969.78 3 28.70 2032.05
1 Bentonite 27.40 1985.50 1996.17
2 27.00 1970.95
3 Based on Table 4.14, Spesific surface area of BFS
2 and Bentonite are 2933.79 cm /gram and 1996.17
2 cm /gram respectively. BFS has specific surface area higher than bentonite. It means that BFS is more reactive than bentonite. It is inline with particle size and SAI data.
Based on particle size data, the amount of BFS particle passing 75 µm is gretaher than bentonite. Based on SAI data, the SAI of BFS is almost 3 times greather than bentonite. The material which has high SSA, SAI, and particle passing 75 µm (smaller particle size), is more reactive than other one. But, any other factors that can influence the reactivity of material, such as chemical properties, ion excangable, type of mineral structure, etc.
4.2.8. Flowability of The Cement Paste Mixture
Flowability test is carried out to determine water per cement ration of each cement mixture (sample) to get same flowability. The floawability was measured by determining average of minimum 2 diameter of the cement paste mixture on the flow table after the table is dropped 25 times in 15 s. The cement paste mixtures used in this
4 B5S30 NA
research was B0S0 (control specimen/100% cement),
B5S0 (cement paste which 5% of the total binder was
replaced by bentonite), B0S30 (cement paste which 30% of
the total binder was replaced by BFS), and B5S30 (cement
paste which 5% and 30% of the total binder were replaced
by bentonite and BFS respectively). The Flowability test
result of the some cement paste mixtures are shown inTable 4.15 and Fig.4.8.
Table 4. 15. Flowability test result of cement paste mixturesNo Sample Water/binder
2 B5S0 NA
*NA : the data was loss, because the cement paste did not
flow and the floawabilty diameter greather than maximumdiameter of the flow table.
Figure 4. 8. Flowability of the cement paste mixture Utilization of bentonite and BFS as partial cement
replacement can decrease flowability of the cement
mixture with contant water/binder ratio. It can be observed
from Fig 4.8, graphic of B5S0, B0S30, and B5S30 are
plotted under graphic of control mixture (B0S0). However,
utilization Bentonite as partial cement replacement can
decrease greatly the flowability of the cement mixture,
compared to mixture using BFS. It can be observed from
Fig 4.8, graphic of B0S30 and B5S30 are plotted slightly
bellow graphic of B0S0 and B5S0 respectively. But the
graphic of B5S0 and B5S30 are plotted far bellow graphicof mixture without BFS (B0S0 and B5S0).
Decrease in flowability by bentonite replacement is
influenced by montmorilonite content of bentonite as
shown in XRD result Table 4.9. The Montmorillonite
mineral can adsorb some water which due to bentonite can
swell. As reported by Lim et all (2013), the swelling
capacity of the bentonite increase by increasing the amount
of water adsobtion. The water will be adsorbed and enter
the space beetween oktrahedral layer and tetrahedral layer
in montmorillonite mineral. Then ion exchange process
occur between bentonite ion and water ion. This ion
exchange process influences specifically to the swelling
capacity and water adsorbtion value. This ion excange
process cause high decrease in flowability of cement pastecontaining bentonite.
Decrease in flowability by BFS replacement is
probably influenced by particle shape of BFS. Based on
Ptacek (2012), BFS had flake particle shape ( shown in
Fig.4.9). Spherical shape can increase the flowability,
because spherical shape is moveable. In other hand, flake
shape may decrease flowability. It is the reason whyutilization BFS can decrease flowability.
Figure 4. 9. SEM image of BFS
( Source : Ptacek, 2012 )
Figure 4. 10. Method to determine w/b for each mixtureThe flowability test result in Fig 4.10 is used to
determine water per binder ratio (w/b) for each mixture. To
determine w/b ratio, the flow of each mixtures was kept
constant at value 22 mm. Then, from flow 22 cm (vertical
axis), it was made horizontal red line until crossing 4
graphic (Graphic B0S0, B5S0, B0S30, and B5S30). Then,
from the intersection beetween horizontal red line and 4
graphic, it was made vertical red line to determine
water/binder ratio (w/b) for each mixtures (See Fig. 4.10).
The water per binder ratio for each mixture is reported inTable 4.16.
Table 4. 16. W/b for each mixture at contant flow 22 cm No Mixture Flow (cm) w/b
1 B0S0 22 0.342
2 B5S0 22 0.421
3 B0S30 22 0.355
4 B5S30 22 0.428
4.3. Testing Result of Self Healing Evaluation
4.3.1. Crack Width
Crack width is one of the parameter to evaluate self healing process over time for different mixtures. Crack width on the surface of concrete was observed by using microscope with 250 times magnification scale. Before the observation process, the specimens were removed from water immersion curing, and dried. For each mixtures, 15 representative crack location were chosen. For each one representative crack location was signed by using water resistant ballpoin to make constant measurement points and to ensure that measurement points were not changed over time. The observation and measurement process were carried out on 0, 3, 7, and 28 age days after introducing artificial crack in the specimens. The objective of this process is to obtain microscopic pictures of the crack evolution over time, the decreasing crack width over time, and the β index over time for each mixture. These parameter are used to evaluate self healing process, where β index is healing effectiveness of cement paste mixtures over time, and it is calculated based on the following equation :
.................................(14) where A o and A t are the area of crack on surface of the speciment at the time 0 and t days respectively after introducing artificial crack. Value of β index is varied between 0 – 1.
The microscopic pictures of the crack evolution over time for small initial crack width in range of 0 – 200 µm are shown in Fig. 4.12. The influence of BFS on the self healing process was observed by using crack closing rate and the healing material closing crack. Utilization BFS as autogenous healing material has slow crack closing rate, compared to specimens without BFS. Cracks on the
specimens without BFS are almost closed completely on
day 7. However, at the same time, specimens using BFS
still did not close perfectly. According to Tittleboom et all
(2012) and Nasir et al (2014), BFS has slow reaction in
the early time and will react in the last time. Based on
isothermal calorimetry testing of cement paste which is
raplaced partially by BFS and reference cement paste,
cummulative heat production of cement paste using BFS is
smaller than reference cement paste in the early time. But
in the last time, cummulative heat production of cement
paste using BFS is higher than reference cement paste.
That is the reasion, why on 7 days, crack on the specimens
using BFS (B0S30 and B5S30) did not close perfectly,
compared to specimens without BFS (B0S0 and B5S0).
But, on the 28 age days curing period, both of thespecimens are closed perfectly.
Figure 4. 11. Position of crack measurement point
1.55 mm Figure 4. 12. Evolution of the surface crack width over time for initial crack width 0 - 200 µm Although utilization BFS as partial replacement has
slow crack closing process than refference mixture, but there
are differences about the material closing crack. As shown in
Fig 4.12, the material closing crack on specimens without
BFS are dominated by white cristal which is identified firltlyas Calcium Carbonate (CaCO
3 ) cristal. But, material closing
crack on the specimens using BFS are dominated by grey
cristal which is indentified firstly as Calsium Silicate
Hydrate (C-S-H) cristal, although precipitation of CaCO
3 cristal still occur.
The influence of bentonite to the crack closing process
is almost same with reference mixture (B0S0). But, on 28
days curing period, white cristal closing crack of the
specimen using bentonite (B5S0) is more dense than
refference mixture (B0S0). This is probably caused by ion
excange capacity of Ca-Montmorillonite on bentonite. When
the crack occur, water can enter inside of the crack and then
react physically with bentonite. In this case, when bentonite
contact with water, water will enter the area between the
tethahedral layer and oktahedral layer of Ca-
Montmorillonite mineral to carried out ion excange process.
The ions are Ca ion from montmorillonite layer and ion
from water. Furthermore, there are additional Ca ion which
is released from this process (Fernandez et al, 2014). This
additional Ca ion will react with C0 ion from the waterenviroment to precipitate CaCO
3 crystal which cause material closing crack more dense.
For the large initial crack width in range of 200 –
350 µm, the crack closing process is slower than smaller
crack width. However, the influence of bentonite and BFS to
the crack clossing process is still similar to the small crack
width. The material closing crack is also similar to previous
small crack width. But, the specimens with BFS did not
close perfectly on 28 age days curing periode. Thus, initial
crack width is very important factor which most influenceshealing process in term of crack closing process .
Figure 4. 13. Evolution of the surface crack width over time
for initial crack width 200 – 350 µm
Figure 4. 14.
Comparison of material closing crack between
mixture using BFS and mixture without BFSBeside the microscopic pictures, evolution of crack
width was gotten by measuring crack width quantitically over
time from different mixtures. The decrease in crack width
over time of the mixture B0S0, B5S0, B0S30, and B5S30 are
shown in Table 4.17 until Table 4.20 respectively. Then theresults are plotted in Fig. 4.15 until Fig. 4.18 respectively.
Table 4. 17.
β index over time for B0S03 7 28 B0F0 3 B2 0,07 0,00 0,23 0,92 1,00 1,00 56 B0F0 1 C4 0,07 0,00 0,56 1,00 1,00 1,00 B0F0 1 A1 0,07 0,00 0,23 0,69 1,00 1,00 B0F0 3 C4 0,10 0,00 0,71 1,00 1,00 1,00 B0F0 1 B2 0,11 0,00 0,32 0,73 1,00 0,91 B0F0 2 A1 0,13 0,00 0,28 0,56 1,00 1,00 B0F0 2 B1 0,13 0,00 0,48 0,82 1,00 1,00 B0F0 1 D3 0,14 0,00 0,03 0,93 1,00 1,00 B0F0 1 B3 0,14 0,00 0,25 0,68 1,00 1,00 B0F0 1 B1 0,15 0,00 0,25 0,48 1,00 0,94 B0F0 3 A1 0,15 0,00 0,23 0,54 1,00 1,00 B0F0 3 B1 0,18 0,00 0,32 0,38 0,89 1,00 B0F0 2 C1 0,21 0,00 0,25 0,50 0,97 1,00 B0F0 3 D1 0,23 0,00 0,30 0,44 1,00 1,00 B0F0 3 C1 0,28 0,00 0,25 0,47 1,00 1,00 1,00 Averagecfor Large Crack (0.20 - 0.35 ) mm 0,00 0,32 0,73 0,99 0,99 0,00 0,27 0,47 0,99 Masurement Time ( age days after cracking) Measurement Point Initial Crack (mm) Average for small Crack (0 - 0.20) mm
With BFS Without BFS 1.55 mm 1.55 mm
Measurement Initial Crack Masurement Time ( age days after cracking) Table 4. 18. β index over time for B5S0 B5F0 3 D1 0,10 0,00 0,04 0,92 1,00 1,00 B5F0 1 B3 0,07 0,00 0,54 1,00 1,00 1,00 B5F0 1 C5 0,09 0,00 0,55 0,97 1,00 1,00 Point (mm)
37 28 56 B5F0 2 C2 0,17 0,00 0,22 0,72 1,00 1,00 B5F0 1 A2 0,16 0,00 0,38 0,91 1,00 1,00 B5F0 3 C2 0,11 0,00 0,34 0,88 1,00 1,00 B5F0 1 A4 0,10 0,00 0,07 0,32 1,00 1,00 B5F0 1 B1 0,19 0,00 0,22 0,55 1,00 1,00 B5F0 2 D1 0,19 0,00 0,22 0,55 1,00 1,00 B5F0 3 B1 0,22 0,00 0,28 0,45 0,98 1,00 B5F0 2 C1 0,30 0,00 0,12 0,50 1,00 1,00 B5F0 3 D1 0,22 0,00 0,21 0,48 1,00 1,00 B5F0 2 A1 0,20 0,00 0,19 0,45 1,00 1,00 B5F0 1 C1 0,20 0,00 0,19 0,25 1,00 1,00 B5F0 3 A1 0,19 0,00 0,19 0,65 1,00 1,00 Averagecfor Large Crack Average for small Crack (0.20 - 0.35 ) mm (0 - 0.20) mm 0,00 0,20 0,43 1,00 1,00 0,00 0,28 0,75 1,00 1,00 Measurement Initial Table 4. 19. β index over time for B0S30 B0F30 2 D5 0,07 0,00 0,17 0,59 1,00 1,00 B0F30 3 C3 0,07 0,00 0,10 0,34 1,00 1,00 Point Crack Masurement Time ( age days after cracking)
37 28 56 B0F30 1 A1 0,09 0,00 0,55 0,99 1,00 1,00 B0F30 2 A3 0,14 0,00 0,07 0,28 1,00 1,00 B0F30 1 C3 0,10 0,00 0,26 0,47 0,88 1,00 B0F30 1 C4 0,12 0,00 0,38 0,71 1,00 1,00 B0F30 2 B2 0,13 0,00 0,16 0,37 1,00 1,00 B0F30 2 B4 0,10 0,00 0,13 0,41 1,00 0,99 B0F30 3 A2 0,20 0,00 0,26 0,47 0,75 1,00 B0F30 1 A4 0,16 0,00 0,55 1,00 1,00 1,00 B0F30 1 A3 0,16 0,00 0,28 0,46 1,00 1,00 B0F30 2 C4 0,18 0,00 0,12 0,76 0,84 1,00 B0F30 2 C2 0,28 0,00 0,11 0,43 1,00 0,98 B0F30 2 C3 0,24 0,00 0,34 0,32 0,74 0,98 Averagecfor Large Crack Average for small Crack B0F30 3 D3 0,35 0,00 0,36 0,28 0,35 0,58 (0.20 - 0.35 ) mm (0 - 0.20) mm 0,00 0,27 0,37 0,71 0,88 0,00 0,25 0,58 0,97 1,00
Table 4. 20. β index over time for B0S30 3 7 28
B5F30 3 A3 0,08 0,00 0,20 0,82 0,97 1,0056 B5F30 2 C5 0,08 0,00 0,18 0,47 0,96 0,99
B5F30 3 D6 0,09 0,00 0,18 0,64 0,86 1,00
B5F30 2 B4 0,09 0,00 0,25 0,74 0,96 1,00
B5F30 3 B2 0,12 0,00 0,20 0,65 0,98 0,98
B5F30 2 B3 0,16 0,00 0,27 0,46 0,98 1,00
B5F30 3 D2 0,17 0,00 0,14 0,55 0,98 1,00
B5F30 1 B1 0,17 0,00 0,26 0,49 0,94 1,00
B5F30 2 D3 0,20 0,00 0,25 0,56 0,96 1,00
B5F30 1 A4 0,24 0,00 0,10 0,20 0,86 1,00
B5F30 1 C3 0,24 0,00 0,09 0,38 0,94 1,00
B5F30 2 B1 0,25 0,00 0,06 0,25 0,66 0,96
B5F30 1 A2 0,26 0,00 0,31 0,38 0,56 0,65
B5F30 2 A2 0,27 0,00 0,08 0,34 0,98 1,00
B5F30 3 D1 0,28 0,00 0,07 0,26 0,73 0,95Averagecfor Large Crack (0.20 - 0.35 ) mm 0,00 0,14 0,34 0,81 0,94 Measurement Point Initial Crack Masurement Time ( age days after cracking) Average for small Crack (0 - 0.20) mm 0,00 0,21 0,60 0,95 1,00
Figure 4. 16. Evolution of crack width for B5S0Figure 4. 17.
Evolution of crack width for B0S30
Figure 4. 18. Evolution of crack width for B5S30Based on Fig. 4.15 – Fig. 4.18, all mixtures (B0S0,
B5S0, B0S30, and B5S30) could heal the crack by itself.
Crack width could decrease from 0 day until 56 day curing
periode. After 28 age days curing period, crack on the
specimens using bentonite (B5S0) almost closed perfectly. At
the same time, crack on specimens using BFS closed
incompletely (plotted data inside red dash circle in Fig 4.17 -
Fig.4.18). Then, after 56 age days curing period, crack on the
all of specimens closed perfectly, except specimens using BFS
which has initial crack width greather than 0.30 mm. This fact
is inline with microscopic picture in Fig. 4.12 and Fig. 4.13,
that the best healing process and healing product in terms of
decrease in surface crack width is mixture using bentonite.
This was caused by additional Ca ion from montmorillonite
which can increase precipitation of CaCO3 crystal.
Dissolution Ca – bentonite in Ca(OH) 2 could increase amount of Ca2+ ion (Fernandez, 2014).
Initial crack width influences significantly to the crack
closing process. All mixtures could heal crack completely on
56 age day, especially for small initial crack width less than
250 µm (0.250 mm) . If the crack width greater than 250 µm,
crack width would decrease incompletely (plotted data inside
red dash circle in Fig 4.17-Fig.4.20). But, mixture using
bentonite (B5S0) could close crack width completely,
followed by reference mixture (B0S0) and mixture using BFS
or bentonite (B0S30 and B5S30). Other mixtures (B0S0,
B0S30 and B5S0) could heal crack width completely for the
maximum crack width 250 µm. An initial crack width of
50um can reduce to 20 um within 24 hours, and that crack
with an inital crack width of between 50 and 100 um reduce to
20 um within seven days due to self healing (Clear in Won,
2013)). Other studies have shown that initial crack width 200
um can completely seal after five to seven weeks of exposure
to a moist enviroment (Edvarsen, 1996). In the wider initialcrack width, self healing is less effective (Sahmaran, 2010).
To make easily analysis, β index was used to evaluate
self healing process both for different mixtures, different
curing time, and differenet initial crack width. Influence of
mixtures (bentonite and BFS), curing time and initial crack
width to the self healing process (shown by β index) are
discused in the next paragraph based on β index parameter.The value of β index is plotted in Fig. 4.18 and Fig. 4.19.
Influence of mixtures (bentonite and BFS) to the self
healing efficienci (β index) on 28 age days and 56 age days
are shown in Fig. 4.19 and Fig. 4.20 respectively. Mixtures
using BFS showed low healing efficiency on 28 age days,
compared to mixtures without BFS. However, on 56 age days
after cracking, all of the mixtures showed great healing
efficiency, except for the large initial crack width in B5S30
mixtures. It means that BFS had slow crack closing rate,
compared to refference mixtures. It was inline with the result
resported by Oliver (2013), that portland cement with 50%
slag replacement has the tendency to a slower self-healing in
an early age than a reference mixtures with 100% portland
cement. It was mainly caused by slow hidration rate of BFS
particle (Tittelboom et al, 2012). Furthermore, its latent
hydraulic behavior is critical to its self-healing in long term
(Oliver et al, 2013). But, after 56 days after cracking, both
specimens using BFS and without BFS showed same healing
efficiency. Beside that, it also means that BFS generally could
only close crack for small initial crack width, especially for
initial crack width less then 0,200 mm. When the initial crack
width greather than 0,200 mm, healing efficiency became
lower. Thus, the influence of BFS is decrease in rate of
healing efficiency, and BFS could only close perfectly forsmall initial crack width less than 0,200 mm.
Beside that, utilization bentonite (B0S0) showed almost
same healing efficiency with refference mixture (B5S30), both
on 28 days and 56 days after cracking. However, B5S0
resulted healing efficency higher than B0S0. Combination
bentonite and BFS resulted decrease in healing efficiency on
28 age days after cracking. But, on same initial crack width,
combination bentonite and BFS (B5S30) resulted higher
healing efficiency than mixtures using BFS (B0S30). This was
caused by additional Ca ion from montmorillonite which canincrease precipitation of CaCO
3 . Dissolution Ca – bentonite containing Ca - Montmorilonite in Ca(OH) 2 solution could
increase amount of Ca ion. Increase in Ca ion couldincrease CaCO
3 precipitation (Fernandez, 2014). Thus, the
influence of bentonite is increase in rate of healing efficiency.
Ca 0.165 Al
4 O 10 (OH)
2 + 2.34Ca(OH)2 +2H
2 O 4− 3− ......(15)
2.505Ca 2+ + 1.67Al(OH) + 4HSiO
Figure 4. 19. β index for different mixtures on 28 days curing periodFigure 4. 20. β index for different mixtures on 56 days curing period
The influence of curing time to the self healing
efficiency are shown in Fig. 4.21 and Fig 4.22. For small
initial crack width in range of 0 - 200 µm, four mixtures
showed same graphic pattern over time from 0 age days until
56 age days after cracking. The differences are taken place on
healing rate over time. In the initial curing period ( 0 days – 7
days), mixtures without BFS (B0FS0 and B5FS0) showed
increasing β index rapidly, while the mixture using BFS (B0S30
and B5S30) showed lower β index (Shown by line gradien). But
on the contrary, in the next curing period (7 days – 56 days),
mixtures using BFS showed line gradien higher than line
gradien of mixtures without BFS. Although on the final curing
time 56 days, both mixtures using BFS and without BFS
shown almost same value of β index . Generally, the healing
process on small initial crack width occured rapidly in the
initial curing period, especially under 7 days after cracking. In
the next curing period, the healing process are slower than inthe initial curing period.
The healing efficiency of the large initial crack width in
range of 200 – 350 µm is almost similar to small initial crack
width. It is shown by same graphic pattern in Fig. 4.21 and
Fig 4.22. However, it has difference in rate of healing
efficiency, where rate of healing for the large initial crack
width is lower than small initial crack width. It is shown by
line gradien of graphic in Fig 4.22 is lower than line gradien
of graphic in Fig 4.21. Beside that, on 56 days curing periode,
mixtures using BFS showed value of β index less than 1,0. Itmeans that crack closed incompletely for large crack width.
Figure 4. 21. β index over time for each mixtures with initial
crack width 0-200 µm
Figure 4. 22. β index over time for each mixtures with
initial crack width 200-350 µmInitial crack width 0 – 200
Initial crack width 200 – 350 µm Both small initial crack width and large initial crack
width could close completely for mixtures without BFS
(B0S0 and B5S0). It can be observed from the β index data
of B0S0 and B5S0, which has value 1.0. But, utilization
BFS as partial cement replacement could decrease β index
over the curing time period, both for small initial crack
width and large initial crack width. As reported by Huanget all (2014), BFS need Ca(OH)
2 as activator to carry out
conitued hydration process. This process will consumesome Ca(OH)
2 resulted from cement hydration. Because the amount of Ca(OH) 2 is decreased, precipitation CaCO
crystal in surface of crack also decrease. Because of that,
material closing the crack on mixture using BFS was
dominated by grey cristal. This grey cristal is identified
firstly as Calsium Silicate Hydrate (C-S-H) resulted from
continued hydration process of Blast Furnace Slag (BFS).
But, this grey cristal can’t close the crack perfectly and it is
limited for the crack width smaller than 0.200 mm. It is
inline with numerical aproach which is conducted by
Edvardsen (1999) and validated by Li et al ( 2007), that
self healing process by continued hydration of unreacted
clinker cement only could occure perfectly for the
maximum crack width 6 µm. But this result is very excited,
that maximum crack width could heal completely by
continued hydration of BFS is greather than the maximum
crack width reported by Edvardsen (1999) and Li et al (2007).
The Influence of initial crack width to the self
healing process are shown in Fig. 4.23. Generally, self
healing process only can occure perfectly for small initial
crack width, and become lower when the initial crack
width is large. For crack width smaller than 0.200 mm, the
value of self healing efficiency index increase rapidly. It is
noticed by plotted data in the grey area Fig. 4.23.
However, when the initial crack width greather than 0.200 mm, self healing efficiency (β index) was lower when compared to the crack having initial crack smaller than 0.200 mm. It is noticed that some plotted data on 28 age days almost doesn’t reach β index = 1.0. The lower healing efficiency occured in specimen which have initial crack width 0.35 mm. Thus, self healing efficiency is influenced significally by initial crack width which occur on the specimens.
Figure 4. 23. β index over the initial crack width
4.3.2. Crack Depth
Crack depth also is used to evaluate self healing process, and to ensure that self healing process is not only occur in the surface of crack, but also occur inside of the crack. For each mixtures, it was choosen 2 measurement point. The measurement crack depth was conducted on 0, 3, 7, 28, and 56 age days after cracking. The result of crack depth measurement is presented in Table 4.21 and then plotted in Fig. 4.24.
Table 4. 21. Existing crack depth for different mixturesAge Existing Crack Depth B0FS00 B5FS00 B0FS30 B5FS30
52,67 49,54 51,20 47,68 53,04 49,51 51,25 47,67 3 52,05 48,58 49,14 45,45
52,06 48,54 49,15 45,72
7 51,79 47,69 47,61 43,52 51,77 47,86 47,60 43,81
28 48,53 44,31 39,63 36,48 48,49 44,33 39,67 34,47
56 46,83 42,11 37,92 33,17 46,86 42,55 37,95 33,14
Table 4. 22. Corrected crack depth for different mixturesAge Corrected Crack Depth by artificial crack (Artifiacial crack is 5 mm in depth) B0FS00 B5FS00 B0FS30 B5FS30
47,67 44,54 46,20 42,68 48,04 44,51 46,25 42,67 3 47,05 43,58 44,14 40,45
47,06 43,54 44,15 40,72
7 46,79 42,69 42,61 38,52 46,77 42,86 42,60 38,81
28 43,53 39,31 34,63 31,48 43,49 39,33 34,67 29,47
56 41,83 37,11 32,92 28,17 41,86 37,55 32,95 28,14
Figure 4. 24 Decrease in crack depth over time for each mixtures Based on Figure 4.24, all mixtures have self healing ability in terms of decreasing crack depth, although it was seem very slightly decrease in crack depth which is identified by using ultrasonic pulse velocity. Crack depth can’t heal perfectly for all mixtures. To make easily analysis, α index (rate of healing) is used to evaluate self healing process both for different mixtures and different curing time. Influences of mixtures (bentonite and BFS) and curing time to the self healing process (shown by α index ) are discused in the next paragraph based on α index parameter. The value of α index is plotted in Fig. 4.14 and calcultaed based on following equation  .
...................................(15) where Cd o and Cd t are the crack depth at the time 0 and t days respectively after cracking. The value of α index is
varied between 0 – 1. The Influence of the mixtures
(bentonite and BFS) and curing time to the rate of healingare shown in Fig.4.25.
Figure 4. 25. Rate of Healing (α index ) over time for each
mixturesThe influence of curing time to the rate of healing
is shown in Fig. 4.25. Rate of healing was changed
rapidly for all specimens under 28 days after cracking.
But, rate of healing becomes lower after 28 days – 56
days curing period. This is noticed by line gradiens under
28 age days is steeper than after 28 age days. This pattern
occur in all mixtures. Thus, healing process in terms of
decreasing crack depth occur rapidly in early time aftercracking, and become lower in the last time.
Utilization BFS as partial cement replacement
(B0FS30 and B5FS30) show higher rate of healing,
compared to the mixtures without BFS (B0FS00 and
B5FS00). It is noticed by graphic B0FS30 and B5FS30
are plotted far above graphic B0FS00 and B5FS00
respectively. Thus, utilization BFS as partial cement
replacement is usefull to generate self healing ability ofthe cement paste, in term of decrease in crack depth.
Utilization bentonite as partial cement replacement
(B5FS00 nad B5FS00) also showed higher rate of healing
than mixtures without bentonite (B0FS00 and B0FS30),
although it was seem very litlle decreasing crack depth. It
is noticed by graphic of B0FS30 and B5FS30 are plotted
slightly above graphic of B0FS00 and B5FS00
respectively. Thus utilization bentonite as partial cement
replacement is rather usefull to generate self healingability in terms of crack depth.
From two fact above, it is contrary with crack
width observation. Based on crack width observation, it
was well known that utilization BFS resulted low healing
effectiveness, compared to other mixtures. But, based on
crack depth measurement, utilization BFS resulted higher
rate of healing, compared to other mixtures. Although
utilization bentonite still show same trend, both in crackwidth observation and crack depth measurement
To discover this fact, some hypothesis are used.
One of them is condition and limitation for continued
hydration which can heal cracks perfectly on the
concrete. As reported by Edvardsen (1999) and Li et al (
2007), that maximum crack width is limited 6 µm in
order crack can heal completely by itself (value of β index is
1.0). If this condition is not fulfilled, the ultrasonic pulse
velocity measurement didn’t show decreasing crack
depth, although based on crack width measurement,
specimen has healed by itself, but incompletely. It was
caused by ultrasonic pulse which only can propagate in
the massive/dense medium such as in concrete material.
If the crack point didn’t heal completely ( value β index
less than 1.0), this ultrasonic couldn’t propagate in this
crack point and there is little or even no decreasing crackdepth are shown.
Crack Depth Inside Crack Crack Width Surface Idealized to Widht b a
Figure 4. 26. Side view of cracks on the concrete a). real crack pattern b) idealized crack pattern Other hypotesis used is shown in Fig. 4.26. In that
pictures, crack is devided into two zone in vertical
direction. The first zone is inside crack zone (the area
inside red rectangular line Fig 4.15). The Second zone is
surface crack zone (the crack area outside red rectangular
line Fig 4.15). If the crack is introduced on the concrete
material, crack width is different between inside crack
zone and surface crack zone. Inside crack zone has
smaller crack width than surface crack zone. Therefore,
when some water enter inside of the crack, inside crack
zone could heal perfectly in terms of continued hydration
of BFS. This process caused ultrasonic pulse velocity
could show decreasing crack depth. But in the surface
crack zone, cracks healed incompletly, because the crack
width is larger than inside crack zone. Thus, ultrasonicpulse didn’t show decreasing crack depth.
Although based on crack width measurement, crack
had healed completely. However, it probably occur only
in the crack surface and the inside of crack healed
incompletely. It is probably caused by healing process
between inside crack zone and surface crack zone are
different. When in the inside crack zone, self healing
process is significantly inluenced by continued hydration reaction. But in the surface crack zone (especially for the crack surface), self healing is significantly influenced by
carbonation reaction. There are possibility that CO2 only available in the surface crack zone and CO
2 couldn’t enter inside of the crack. Thus, self healing process in terms of carbonation reaction mainly occurs in the surface crack area.
It can be concluded based on crack depth measurement that utilization BFS give higher decreasing crack depth, when compared with refference mixture. But utilization bentonite showed little decreasing crack depth.
4.3.3. Direct Tensile Regain
Direct tensile test is also carried out to determine the self-healing process in terms of mechanical regain. For each mixture, three specimens were used. Each specimen was subjected to the direct tensile test on 28 age days after casting to introduce artificial crack and to determine tensile strength properties for each mixture on 28 age days after casting. After that, specimens were cured in water immersion curing for 56 age days after introducing artificial crack. After 56 age curing period, specimens were removed from specimen holder and subjected to the direct tensile test again to proof that self- healing process occur, in terms of tensile regain. The direct tensile test results before and after healing are shown in Table 4.23 and Table 4.24 respectively, and the data are plotted in Fig. 4.27 and Fig.4. 28 respectively.
B0FS30 B0FS00 B5FS30
906 9055 14036
Postcracked Tensile Strenth 28 age days 12,57
Sample Code B0FS00 B5FS00 B0FS30 B5FS30 19,82 16,07 10,78
Sampel 1 1,305 13,05 20,23
Sampel 2 1,252 12,52 19,41Sample 3
Sampel 1 0,678 6,78 10,50
Sampel 2 0,944 9,44 14,64Sample 3
16743 Sample Code Precarcked Tensile Table 4. 24. Tensile strength before cracking P (Kg) P(N) Kpa Average
Sample 3 911 9109 14119 Sampel 1 823 8233 12762 Sampel 2 803 8029 12445 Sample 3 825 8251 12790
Table 4. 23. Tensile strength before cracking P (Kg) P(N) Kpa Average
939 9393 14560
1032 10318 15993
980 9800 15191
987 9867 15294
Sampel 1 1089 10890 16879 Sampel 2 1075 10751 16664 Sample 3 1077 10765 16686 Sampel 1
- Sampel 1 0,754 7,54 11,69 Sampel 2 0,637 6,37 9,87
Sample 3 - - -
- Sampel 1 1,174 11,74 18,20 Sampel 2 0,899 8,99 13,94
B0S0 B5S0 B0S30 B5S30 Figure 4. 27. Tesile strenght before healing of some mixture on 28 age days after casting.
Based on Fig. 4.27,, utilization BFS as partial
cement replacement could decrease significantly the direct
tensile strength of the cement paste mixture on 28 age days.
The tensile strength of the mixture using BFS (B0S30) is
14462.92 Kpa. This value is smaller than tensile strength of
reference mixture (B0S0) with tensile strength value 16545.88
Kpa. Decreasing tensile strength of mixture using BFS is also
shown by mixture B5S0 and B5S30. The tensile strength of
mixture B5S30 is 12665.55 Kpa. This value is also smaller
than tensile strength of mixture B5S0 with tensile strength
value 15492.30 Kpa. This tensile strength trend is inline with
compressive strength trends reported by Palin et al (2015).
Although, compressive strength show different properties
from tensile strength, but both of them show mechanical
properties of the cement mixture. Before submersion, OPC
mixtures began with somewhat higher compressive strengths
than mixtures using BFS, and these roles were reversed by day
28 with specimens using BFS having slightly higher
compressive strengths than OPC specimens (Palin et al, 2015). Decreasing tensile strength on 28 age days by BFS
replacement is mainly contributed by slow reaction properties
of BFS particle in the early time. Based on the reactivity test
result in previous subchapter, reactivity of BFS particle is
0.73. This value indicate that reactivity of BFS particle is 27%
lower than reactivity of OPC particle. Besides that, it is well-
known that slag particle can be activated by solution which
has Ph higher than 12 (Bijen on Huang et al, 2014). In thecement matrix, this high ph is attributed by Ca(OH) 2 solutions
resulted from cement hydration. The amount of Ca(OH)
resulted from cement hydration could reach almost 100% on
28 age days (Mulyono, 2003). Because of cement clinker is
replaced by BFS, the amount of Calsium Silicat Hydrates (C-S-H) and Ca(OH)
2 resulted from cement hydration decrease.
Decreasing Ca(OH) 2 can decrease ph in the cement matrix.
Decreasing Ph can obstruct the BFS activation process. This
process can decrease the amount of C-S-H resulted from
hydration of BFS particle. Decreasing amount of C-S-H can
decrease mechanical properties of the cement mixtures.Thus,
BFS replacement can decrease a tensile strength on early age.
Based on Fig. 4.27,, utilization bentonite as partial
cement replacement can decrease slightly the direct tensile
strength of the cement paste mixture on 28 age days. The
tensile strength of mixture using Bentonite (B5S0) is
15492.30 Kpa. This value is smaller than tensile strength of
reference mixture (B0S0) with tensile strength value 16545.88
Kpa. Decreasing tensile strength of mixture using bentonite is
also shown by mixture of B0S30 and B5S30. The tensile
strength of mixture B5S30 is 12665.55 Kpa. This value is also
smaller than tensile strength of mixture B0S30 with tensile
strength value 14462.92 Kpa. This tensile strength trend is
inline with compressive strength trends reported by Akbar et
al (2014). Although, compressive strength show different
properties from tensile strength, but both of them show
mechanical properties of the cement mixture. The 7, 14, 28,
56 and 91-day compressive strengths of Bentonite-cement
mixtures are 77.03, 69.39, 76.07, 83.31 and 90.03 percent
respectively as that of control mixtures. It can be concluded
that, strength of Bentonite samples is not appreciable in the
early age. But in later age, strength of Bentonite sample is
quite appreciable, but still lower than reference mixture(Akbar et al, 2014).
Decreas in tensile strength by Bentonite replacement is
mainly contributed by low reactivity of bentonite. This is
caused by the bentonite was dominated by crystalline mineral
and the reactivity of Bentonite is very low (0.15), as explained
in reactivity test result and XRD result. Because of cement
clinker is replaced by Bentonite, the amount of Calsium
Silicat Hydrates (C-S-H) resulted from cement hydration
decrease. Decreasing amount of C-S-H can decrease the
mechanical strength of the mixtures. Because the bentonitereplacements 5%. Thus tensile strength decrease slightly.
B0S0 B5S0 B0S30 B5S30 Figure 4. 28.
Tesile strenght regain after healing of some mixture on 56 age days after cracking Fig. 4.28 shows tensile strength regain on 56 age days after cracking for different mixtures. Although the tensile strenth regain after cracking show lower tensile
strength than before cracking, but there are some
differences in tensile strenght regain for differentmixtures (BFS and bentonite).
The tensile strength recovery for specimens using
bentonite is lower than specimens without bentonite. It is
noticed that tensile strength of B5S0 and B5S30 are
higher than B0S0 and B0S30 respectively. This trend is
inline with tensile strength properties before cracking. It
is mainly caused by low reactivity of bentonite. This is
caused by bentonite dominated by cristaline mineral and
reactivity of Bentonite is very low (0.15), as explained in
reactivity test result and XRD result. Beside that, the
bentonite particle couldn’t be acivated in the last time
like BFS particle. Thus, bentonite could decrease the
tensile strenght both in the early age and last time.
Because of cement clinker is replaced by Bentonite, the
amount of Calsium Silicat Hydrate (C-S-H) resulted from
cement hydration decrease. Decreasing amount of C-S-H
can decrease mechanical strength of the cement mixtures.
Because the replacement only 5%, thus the tensilestrength decrease slighly.
The tensile strength recovery for specimens using
BFS is higher than specimens without BFS. It is noticed
that tensile strength of B0S30 and B5S30 are higher than
tensile strength of B0F0 and B5S0 respectively.
Although before cracking, utilization BFS show lower
tensile strength than specimens without BFS, but this
roles is reversed after cracking. BFS result higher
mechanical properties in the last time. It is caused by
laten hydraulic properties properties of BFS (Titleboom,2014). It mean that BFS need Ca(OH)
2 to activate its
particles in order hydration reaction can occur. Ca(OH)
is resulted completely from hydration reaction on 28 age
days. Thus, the tensile strength of mixtures using BFS is
lower than mixtures without BFS, because some unreacted BFS particle still available in the cement matrix (Zhong, 2012). Beside latent hydraulic properties of BFS, it is also caused by slow reaction properties of BFS. In the early age, hydration reaction of BFS is very low, and the hydration reaction occur rapidly in the last time (Lothenbach, 2012).
4.3.4. Flexural Recovery
Four points bending test are also carried out to determine the self-healing process in terms of flexural regain. For each mixture, 3 specimens were used for this testing. Each specimen was subjected to the four point bending test on 28 age days after casting to introduce artificial crack and to determine flexural properties for each mixture on 28 age days after casting. Then cracked specimens were cured in water immersion curing for 56 age days after artificial crack was introduced. After 56 age days curing periode, specimens were removed from curing chamber and subjected to the direct tensile test again to determine flexural recovery after cracking. The four points bending test results for 4 mixtures are shown in Fig. 4.29 and Fig.
4.32 respectively. max P cracking
P Figure 4. 29.
Load – deflection curve of mixture B0S0 max
Figure 4. 30 . Load – deflection curve of mixture B5S0
Figure 4. 31. Load – deflection curve of mixture B0S30
Figure 4. 32. Load – deflection curve of mixture B5S30
Figure 4. 33. Load – deflection curve of all mixtures The result of four point bending test is force –
diplacement curve four each mixtures, and it is presented in
Fig.2.28 until Fig. 2.32 respectively. From this curve, it had
been analyzed about the healing process in term of flexural
recovery properties. To evaluate self healing process in
terms of flexural recovery, two parameters were used,
including the decrease in flexural stiffness, and the P max /P crackratio for each mixtures.
All curve in Fig 2.28 – Fig 2.32 show a similar
pattern in the initial loading stage. In the initial loading
stage, the curves increase slightly up to deflection around 1.0
mm. In this condition, the tensile stress is applied on the
outer layer of beam section, that is healing material (healed
crack). The force applied in this stage is very small. Since,
the direct tensile strengths of healing materials are very
small as shown in direct tensile test result, the crack on this
healing material occurs. Then, in the second loading stage,
the curves increase steeply. In this stage, tensile stress is
applied in point, which has high-stress concentration (shown
by a red circle in Fig. 4.34). Because the strength of cement
paste is higher than healing material, the curve increases
steeply. After that, crack occurs on this high-stress
concentration point. The model used to describe this processis drawn in Fig.4.34.
Figure 4. 34. Model to analyze load – defelction curve Crack occur on poin of high stress concentration
Crack occur on healed crack Figure 4. 35. Crack occurence in load-deflection curve The flexural stiffness of each beam specimen (Kb)
was determined based on value of elastic modulus of beams,
beams span, and inertia moment of the beam section. It wascalculated based on the following equation:
.................................................(14) Where :
2 K b = Flexural stiffness (kN.m )
4 I = Inertia moment of beams section (m ) L = Beams span ( m )
2 E = Elastic Modulus ( kN/m ) Inertia moment of beam’s section is determined by using following equation :
......................................(15) Where :
4 I = Inertia moment of beam’s section (m ) b = Beam’s width ( m ) d = Effective depth of beams (mm)
There are two condition to determine depth of beam, that is depth of beam before cracking and after healing process. The effective depth of beams for each condition is calculated as follows : uncreaked beams = 100 mm – crack depth initiation
1. d = 100 mm – 5 mm = 95 mm cracked beams = 100 mm – crack depth initiation – Cd
2. d d cracked beams = 100 mm – 5 mm - Cd d cracked beams = 95 mm - Cd Where Cd is crack depth for each mixture at measurement time 0 days after cracking. The value of Cd is gotten from crack depth measurement.
Table 4. 25.
Calculation of flexural stiffness of beams specimens for each mixtures    = Δ  / Δ      = 95 mm -    = x/  = K b B - Kb A A A 1 1,77 1,03 B 2 21,52 3,36 B 1 13,24 1,25
A 2 4,28 0,64 A 1 18,39 2,60 B 2 3,18 1,25 B 1 15,17 1,39 2 2,25 0,37 A A 1 14,56 1,93 B 2 1,77 0,79 B 1 16,47 1,48 A 2 2,76 0,45 1 12,36 2,50 A B 2 2,57 1,38 B 1 6,55 0,84 2 1,64 0,37 0,33 0,26 0,28 0,21 Decrease in Flexural Stiffness 300,00 300,00 300,00 300,00 Flexural Stiffness 0,0247 0,3539 0,0402 0,3041 0,0432 0,3192 0,0349 0,2490 Inertia Moment (I) 872946,22 7144791,67 1071955,59 7144791,67 d uncrack specimsn (mm) - 95,00 - 95,00 Cd (mm)
44,52d crack specimsn (mm) 47,14 - 50,48 P (kN) f (mm) Elastic Modulus of Beam Beam Width, b (mm) Beam Span, L (mm) Kode sample
B5S30 8,76 10,45 100,00 100,00
-52,33 - - 95,00 1194183,20 7144791,67 B0S30 11,20 13,40 100,00 100,00
-51,78 - - 95,00 1156924,16 7144791,67 B5S0 11,25 12,77 100,00 100,00 - - 300,00 300,00  B0S0 8,48 14,86 100,00 100,00 300,00 300,00 (kN/mm) (mm 4 ) (kN.m 2 )
Figure 4. 36. Flexural stifness before (B) and after (A)
healing process for different mixturesSelf-healing process in terms of flexural
stiffness regains of some mixtures are shown in Figure
4.36. The results show that flexural stiffness of all
mixtures after healing (A) process are decreased,
compared to before healing process (B). Mixtures using
bentonite and BFS show higher flexural stiffness after
healing process, compared to reference mixture. The
decreases in flexural stiffness for all mixtures were
caused by the crack did not heal perfectly. It has been
shown by crack depth measurement that the maximum
rates of healing of all mixtures are around 0.35, in terms
of crack depth. Because crack depth did not heal
perfectly, the effective depth of beams will decrease and
the inertia moment also decreases. Thus, the flexural
stiffness of all mixtures after healing process (A) arelower than before healing process (B).
However, the flexural stiffness of the mixtures
using BFS is higher than the other mixtures. It is inline
with tensile recovery results that specimens using BFS
show higher tensile strength recovery after healing. It is
due to latent hydraulic properties of BFS. Furthermore,
smaller crack’s depth (Cd ) also can influences thisflexural stiffness value.
Table 4. 26. P cracking and P max ratiofor different mixturesCode Unit B0FS00 B5FS00 B0FS30 B5FS30 P Kgf 1366,08 935,37 1732,84 716,19 P Kgf 2246,56 2505,47 2452,90 2044,21 crack max P /P - max crak 1,64 2,68 1,42 2,85
Figure 4. 37. P cracking and P max for different mixtures P max /P cr ratio is used to evaluate self healing process.
The result shows that mixtures using bentonite resulted highest P max /P cr ratio. However, mixture B0S30 show lower P max /P cr ratio, compared to other mixtures. It shows different result with other parameter such as tensile strength and flexural stiffness. It is due to mechanism to reach P max is different from mechanism to determine tensile strength and flexural stiffness. Both tensile strength and flexural stiffness, stress working in the cement paste beam is dominantly influenced by tensile stress. But in the mechanism to reach P max is different. Load is applied to the beam until beam failure. It means that compression stress of cement paste in the top layer of beams is contributed significanly the value of P max . Thus, it can’t be concluded.
Alkalinity is also measured for different mixtures, both inside crack area and inside cement paste. This measurement is very important to analyze that carbonation
Table 4. 27. Ph measurement result for different mixtureinside cement paste
No Mixtures Sample Code ph Average
1 B0S0 A1x 12,00 11,00 A2x 10,00
2 B5S0 B1x 11,85 11,88 B2x 11,70
3 B0S30 C1x 11,15 10,55 C2x 10,50
4 B5S30 D1x 11,20 10,87 D2x 10,55 D3x 10,85
Table 4. 28. Ph measurement result for different result inside Crack
No Mixtures Sample Code ph Average
1 B0S0 A1c 9,55 9,40 A2c 9,35 A3c 9,30
2 B5S0 B1c 9,90 9,52 B2c 9,35 B3c 9,30
3 B0S30 C1c 9,40 9,53 C2c 9,10 C3c 10,10
4 B5S30 D1c 10,35 9,73 D2c 9,55
B0S0 B5S0 B0S30 B5S30
Figure 4. 38. Ph value for each mixture
From the ph measurement, all mixtures had
almost same ph value. However, ph of the specimens
inside crack and inside specimens was different. Ph of the
specimens inside the crack was lower than inside
specimens. It was due to carbonation reaction occur in that
crack's area. Ph of the cement paste was influenced
significantly by Ca ion, which is come from Ca((OH)2 .
Because the carbonation reaction occurs inside the crack,Ca((OH)
2 inside crack decrease. Low Ca((OH)2 content
could decrease ph. Thus, decreasing ph shows that self-
healing process, which is contributed by carbonation
reaction occurs in the specimens. However, utilization BFS
as partial cement replacement could decrease the ph value,
both inside specimen and inside crack. It was noticed that
ph of mixtures B0S30 and B5S30 were higher than B0S0
and B5S0 respectively. On the other hand, utilization
bentonite as partial cement replacement could increase ph
value. It was noticed that ph of mixtures B5S0 and B5S30
were higher than B0S0 and B0S30 respectively. Based on
this fact, utilization BFS could decrease self-healing
process (carbonation reaction), while utilization BFS could
increase self-healing process in terms of carbonationreaction.
X-Ray Diffraction testing is carried out to identify mineral closing crack for different mixtures. Beside that, this XRD analysis is used to verify healing mechanism which is occured for different mixtures. The XRD result of mineral closing crack for mixture B0S0, B5S0, B0S30, B5S30 are shown in Fig 4.39, Fig. 4.40, Fig. 4.41, and Fig 4.42 respectively. c = Calcite p = Portlandite g = Gypsum b = Bassanite a = Andradite m = Magnesite q = Quartz v = Vaterite t = Thernardite
Figure 4. 39. Diffractogram of mineral closing crack for mixtures B0S0 c = Calcite p = Portlandite g = Gypsum b = Bassanite a = Andradite m = Magnesite q = Quartz v = Vaterite t = Thernardite
Figure 4. 40. Diffractogram of mineral closing crack for mixtures B5S0 c = Calcite p = Portlandite g = Gypsum b = Bassanite a = Andradite m = Magnesite q = Quartz v = Vaterite t = Thernardite
Figure 4. 41. Diffractogram of mineral closing crack for mixtures B0S30 c = Calcite p = Portlandite g = Gypsum b = Bassanite a = Andradite m = Magnesite q = Quartz v = Vaterite t = Thernardite
Figure 4. 42. Diffractogram of mineral closing crack for mixtures B5S30 c = Calcite p = Portlandite g = Gypsum b = Bassanite a = Andradite m = Magnesite q = Quartz v = Vaterite t = Thernardite B0S0
B5S0 B0S30 B5S30 Figure 4. 43. Comparison diffractogram for different mixtures Based on diffractogram in Fig. 4.39 – 4.43, mineral closing crack is dominated by calcite (CaCO 3 ) and portlandite (Ca(OH) 2 ). Besides that, gypsum, bassanite, and magnesite also be present inside of crack for all mixtures, but in small portion. Replacement some clinker with bentonite resulted addition Quartz (SiO
2 ) pick (shown by red circle in Fig. 4.43). This is probably due to quartz mineral contained in bentonite did not react with Ca(OH)
2 , because of the reactivity of bentonite is very low (such as reported in reactivity testing result). On the other case, replacement some clinker with BFS shows almost similar mineral to the reference mixtures. However, combination bentonite and BFS show additional mineral Vaterite. This Vaterite mineral has a similar structure to Calcite. Both of them had a chemical formula CaCO 3 . Nevertheless, chemical structure of Vaterite mineral is more dense than Calcite mineral.
Although, mineral closing cracks for all mixtures are almost same, but percentage for each mineral is different. The percentages of mineral closing crack for each mixture are shown in Table 4.28..
Table 4. 29. Mineral Chemical Formula Unit Percentage of mineral closing crack % 21,66 21,41 10,87 3,07 Percentage of mineral for each mixture ( % ) B0FS00 B5FS00 B0FS30 B5FS30 Portlandite Ca(OH) 2 Calcite CaCO % 73,83 68,74 83,58 85,93 3 % 2,14 1,68 3,09 3,59 Gypsum CaSO (H O) 4 2 2 % 0,82 0,64 0,88 0,47 Bassanite CaSO (H O) 4 2 0.5 Magnesite MgCO % 0,58 0,46 0,58 0,02 3 % 0,96 0,25 0,21 -
Andradite Ca3Fe (SiO4) 2 3 - % 7,07 0,76 5,07 Quartz SiO 2 Gismodine CaAl Si O .4H O % 0,63 - - - 2 2 8 2 % 19,91 - - - Vaterite CaCO 3 Na SO - - - % 1,00 Thenardite 2 4Gambar 4.44. Percentage of Calcite and Portlandite
Mineral inside crackUtilization BFS as partial cement replacement
could decrease the amount of portlandite inside crack area.
It is due to BFS consume portlandite to carry out hydration
reaction. On the other hand, utilization bentonite as partial
cement replacement aslo can decrease the amount of
portlandite inside crack area. Futhermore, since the
portlandite is resulted from hydration of cement clinker,
replacement some cement clinker by BFS and bentonitealso can decrease the amount of portlandite.
BFS could increase the amount of calcite mineral. However, bentonite could improve the amount of CaCO 3 (
specimens B5S30). However, 5% bentonite replacement
could decrease the amount of calcite (B5S0). It is contrary
with crack depth measurement, and ph measurement which
is shown that bentonite could decrease crack width slightly
and bentonite could increase ph inside crack area. It is
probably due to error in sampling of XRD sample for
specimens B5S0. On the other case, combination bentonite
and BFS resulted different mineral from others, that isVaterite.
4.4.1. Influence of Bentonite to the Self Healing
Theoretically, Ca - bentonite could improve precipitation of CaCO 3, especially on the surface of crack. According to Fernandez (2014), bentonite could increase
2+ 2+ Ca ion besides Ca ion from Ca(OH) 2 resulted from cement hydration. It was also proven by the ph results, that bentonite increases ph of the specimens both inside crack and inside specimens. Based on microscopic observation, bentonite shows highest healing effectiveness in terms of crack width and crack depth. It is caused by addition of
2+ Ca ion from Ca-bentonite. From XRD result, specimens using BFS (B5S0) show higher CaCO
3 content inside crack area. The CaCO 3 is structured by Calcite mineral and Vaterite mineral. But, on the contrary, specimens B5S0 shows the decrease in CaCO 3 content. It is probably due to
error in sampling of XRD sample for specimens B5S0.
However, bentonite could decrease the mechanical properties of the specimens after healing process, especially in terms of tensile strength and flexural stiffness. It was mainly caused by low reactivity of bentonite particles. Based on SAI result, reactivity index of bentonite was 0.17. On the other hands, diffractogram of bentonite particles showed that bentonite had crystalline structures. Addition bentonite to the cement paste mixture is not appreciable in the early age. However, in later age, strength is quite appreciable, but still lower than reference mixture (Akbar et al, 2014).
It can be concluded that utilization bentonite as partial cement replacement could improve the self-healing process, especially in terms of decrease in crack width significantly and decrease in crack depth but slightly. On the other hand, utilization bentonite as partial element replacement shows the lowest tensile strength after healing process, compared to the other mixtures.
4.4.2. Influence of BFS to the Self Healing
Generally, BFS could improve self healing process for all of healing parameters, incuding decrease in crack width, decrease in crack, tensile strength recovery, and flexural stiffnes recovery after healing process. However, the tensile strength and flexural stiffness after healing process did not reach the tensile strength and flexural stiffness before cracking.
Utilization BFS as partial cement replacement resulted lower crack closing process. Although it could close crack completely on 56 days after cracking. Low crack closing process was caused by chemical properties of BFS. It has slow hydration reaction compared to clinker cement hydration (Lothenbach, 2012). BFS also has latent hydraulic properties. It means that, besides using water as reactant, hydration reaction of BFS consums Ca(OH)
2 (Huang, 2012). Therefore, the amount of Ca(OH) 2 in the cement matrix decrease. Consequently, precipitation of Ca(CO 3 crystal decrease. But in the later age, cracks had been closed perfectly.
BFS also could improve rate of healing significanty, in terms of crack depth. Higest rate of healing by BFS replacement was significantly influenced by slow reaction of BFS particle. On the other hand, BFS resulted higher tensile strength and flexural stiffness after healing process, compared to other mixtures. According to Lothenbach (2012), for specimens containing BFS, the portlandite content increases up to 48 h after mixing and decreases continuously after that. Beyond 48 h, the hydration kinetics of clinker is slowed by the formation of hydration products around the grains of clinker. During this time, the slag hydration reactions progress and consume the portlandite produced by the clinker in blended cements to produce C-S-H due to the presence of amorphous silica in steel slag (Pane, 2005) as shown in stociometry equation bellow.
3Ca(OH) 2 + 2SiO
2 + H
2 O 3CaO·2SiO 2 ·4H
2 O This C-S-H gell resulted from continued hydration of BFS could close inside crack completely. Thus, ultrasonic pulse could propagate in the inside crack zone, and crack depth could decrease significantly compared to other mixtures. Beside that, highest tensile recovery and flexural stiffness after healing process were significanfly contributed by this C-S-H gell. Thus, BFS could improve healing process, especially in terms of crack depth, tensile strength recovery, and flexural stiffness recovery after healing process.
4.4.3. Correlation between w/b and healing ability
Generally, the self healing mechanism in this researchs was mainly affected by carbonation reaction, although continued hydration still occur. In case of carbonaion reaction and continued hydration, low water per cement ratio can decrease precipitation of CaCO
3 crystal after 28 age days and can improve continued hydration process after 28 age days. According to Breugel (2012), in the normal concrete, hydrated cement grain can reach up to 70% - 80%, and the amount of unhydrated cement is 20% - 30%. Lower water per cement ratio can increases the amount of unhydrated cement grain, which very beneficial for self healing concrete. Because of Low w/c decreases the amount of hydrated cement, the amount of Ca(OH) 2 on 28 age days also decreaes. Thus for cement paste which has low w/c ratio, self healing concrete in terms of carbonation reaction will decreases. On the other hand, water used in concrete are used as reactan in hydration reaction, evaporate in the atmosphere, and
retained inside concrete matrix. This water which is
retained inside the concrete matrix is very important as
water internal curing(Qian et al, 2010). This water is very
beneficial to produce self healing process in terms of
continued hydration. Since the w/c binder ratio increases,
the amount of retained water also increases. This retained
water is very beneficial to hydrate cement clinker or BFS.
In this reseach, four mixtures were studied, i.e
B0F00, B5F00, B0F30, and B5F30 with water per binderratio (w/b) 0.342, 0.421, 0.355 and 0.428 respectively.
Curing periodGambar 4.45. Correlation w/b to the rate of healing
From the Figure 4.45, since the w/b ratio
increases, the rate of healing also increases for all curing
priode (Qian, 2010). Cement paste which has high w/b
ratio, has high retained water in the cement paste matrix.
This water is very beneficial to hydrate BFS particles and
unhydrated cement grain. The continued hydration process
was shown by the decrease in crack depth which is definedas rate of healing ( α index ).
CHAPTER V CONCLUSIONS
The influences of bentonite and blast furnace slag on the self-healing of contentious composites are investigated. The self-healing properties are evaluated using four parameters, including surface crack width (β Index ), crack depth (α Index ), direct tensile recovery, and flexural stiffness recovery. In combination with microscopic observation, a healing process over time is drawn. The following conclusion can be made from this research result:
1. With regard to crack width, bentonite can accelerate crack closing rate. However, BFS could decrease crack closing rate. Although both, can close crack completely on 56 days after cracking, but BFS shows slow crack closing rate than bentonite and reference mixtures.
2. With regard to crack depth, BFS can decrease crack depth significantly, compared to other mixtures, although bentonite also can decrease crack depth but slightly.
3. With regard to tensile strength recovery, BFS produces higher tensile strength recovery after cracking compared to other mixtures, where bentonite shows lower tensile strength recovery after cracking.
4. With regard to flexural regains, all mixtures show lower flexural stiffness after healing process, than before healing process. However, specimens using BFS have higher flexural stiffness, compared to other mixtures.
5. Based on XRD and ph measurement results, the self- healing process is influenced significantly by carbonation reaction.
Some recommendations to the next researchers, who are interested to continue this research are described as follows:
1. Blast furnace slag is very potential used to produced self- healing properties, but high reactivity and low reactivity of BFS could decrease self-healing properties. Thus, it must be studied about the optimum specific surface area (SSA) to produced high self-healing properties.
2. In terms of carbonation reaction, bentonite could increase healing properties. However, in terms of swelling properties, Ca – bentonite didn’t show healing process. Thus Na – bentonite is recommended to self-healing properties in terms of swelling process.
3. Bentonite used in this research has low reactivity. Thus, its need to be activated, firstly, before it mixes with cement.
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BIOGRAPHYThe author was born on 11 July 1993 in Nganjuk, East Java. He is the first child of four childreen from Supriyadi and Partutik. He completed his elementary education in Kepanjen, Pace, Nganjuk. Then he continued his nd eduction in 2 Junior high school of Nganjuk.
After he finished his education in Junior high, nd he joined study in 2 Senior High School of Nganjuk. Then, he continued his study in Civil Engineering Department, Faculcy of Civil Engineering and Planning, ITS and graduated on
March 2016. The author started his career as engineer staff inConstruction Comapany PT. Pembangunan Perumahan (PT.PP).
During his study in Civil Engineering Departmenet ITS, the
author is very active both in academic, organization, competition, and
reseach. In academic, he passed 152 credit include this final project
report with GPA 3.88. In organization, he is active as staff in Reseacrh
and Technology Departement of HMS ITS 2012/2013, Head of
Department in Reseacrh and Technology Departement of HMS ITS
2012/2013, coordinator of National Concrete Competition CIVIL EXPO
2014, etc. In competition, he has won several national competition, suchst nd
as 1 winner of Kompetisi Rancang Bangun in Udayana University, 2nd
winner of National Reseach Competition in University of Indonesia, 2st
winner of National pervious concrete competition in ITS, 1 winner ofst
Geopolymer Concrete Competition in PNJ, 1 winnner of integralnd
colour concrete competition in Petra Cristiany University, 2 winner of
scientific paper competition in UNS, Gold medal of PKM-KC category
in PIMNAS – 27 semarang, etch. In research, he ever studied about
utilization bone waste as partial cement replacement, pervious concrete
using slag waste, geopolymer concrete using bone ash, and self healing
concrete using bentonite and blast furnace slag. He has published histh
one research result on 7 National Conference of Civil Engineering in
2013. Now, his reseach focus on durability of the concrete material by
spplying self healing concrete using geoomaterial. For further
information related to this reseacrh, please contact the author through an
email inor phone number in 085708509743.