Influence Of Bentonite And Blast Furnace Slag To The Self Healing Behaviour Of Cracked Cement Paste - ITS Repository


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  Keyword : cracks, self-healing, durability, bentonite, blast furnace slag PREFACE Thank to Almighty God who has given His favor to the author for finishing the research and completing the final projectreport entitled ""Influence of bentonite and blast furnace slag to the self-healing behavior in cracked cement paste". This reasearch focus on the influence of bentonite and blast furnaceslag to the self-healing behaviour which is evaluated by using 6 parameters, i.e crack width, crack depth, tensile strengthrecovery, flexural stiffness recovery, pH, mineral closing crack, and cloride ion penetration to analyze the durability of thecracked cement paste.

1.1. Background

  Besides the swelling process and carbonation process, the self-healing mechanism is also influenced by the hydrationreaction, both continued hydrations of unreacted clinkers and hydration reaction of some latent hydraulic material such asBlast Furnace Slag (BFS). In this research, self-healing property of cracked cement paste is discussed, including physicalproperties (decrease in crack width and crack depth), chemical properties (mineral of healing product), and mechanical regainproperties (direct tensile strength and flexural strength).

1.2. Research Problems

  How bentonite and BFS influences self healing propertis of cracked cement paste? How about the self healing mechanisms occur in cement paste incorporating bentonite and BFS as a partialcement replacement?

1.3. Research Boundaries

  The self-healing is evaluated only by measuring four parameters, include crack width, crack depth, directtensile recovery, and flexural stiffness recovery of the cement paste after cracking. Cement which is used in this research is cement type 1(Ordinary Pprtland Cement) 4.

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

  To analyze the influence of bentonite and BFS to the crack depth of cement paste after cracking. To analyze the influence of bentonite and BFS to crack width of cement paste after cracking.

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 apartial cement replacement

1.5. Benefits

Benefits of this research are described as follows:

1. As a reference to next researchers about self-healing properties of cracked concrete

  This research is expected to reduce and solve crack problems, which occur in concrete structures, especiallyfor undetected and unreached crack position. As a supporting research to develop alternative cement products, which can be used to overcome the crack'sproblem in concrete structures.


2.1. Crack on the Concrete Structures

  Inhardening concrete, micro crack is very hard to be measured because of the crack width is too small. Minimum crack width which can be observed by the eye is 0.13 mm (0.005 in), and it is belonged to microcracks.

2.2. Conditions for Self-Healing

  Water, water is very important to the all of self healing mechanisms. Thus, in the large crack width, self healing prosessstill 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

  But Van Breugel (2003)reported that limit of a maximum cracks width is determined based on the water pressure which can enterinside of the cracks, such as shown in the 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.

2.3. Self-Healing Mechanism

  This is proven by reinhard(2013), that permeability on the crack area decrease less than 10%, in term of swelling process of HCP. When cracks occur, water will go through inside of cracks and react with UCP, in term of hydration Beside continued hydration, self healing process based on chemical causes are also contributed bycarbonation reaction.

2.4. Self-Healing Mechanism with Continued Hydration

  Edvardsen (1996) made analytical calculations to simulate hydration process of the clinker cement. Model used forcalculating continued hydration process of clinker cement is shown in the Figure 2.3.

a. All these particles cements have same diameter size 50

3 V

  This 1 Δw = (r ⋅ r= 31.5 μm 1/3 = 2 1 = 2V r 3 = 4/3 ⋅ π ⋅ r Edvardsen (1996) used some assumptions to calculate hydration of clinker cement, as follows: 1 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. After the hydration process occur completly, the volume of hydration particles cement which has been hydrated is2 times from initial volume of undydrated cement particles before hydration process.

2.5. The influence of Pozzoland to Ca(OH) content

  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

  Additional fly as, bothin cement portland and blast furnace slag cement are able to 2 reduce the amount of Ca(OH) at the age 365 days. The 2 amount of Ca(OH) for cement portland and blast furnace slag cement are 8 gram/100 grams and 3 grams/100 gramsrespectively.

2.6. Characteristics of Bentonite Clay

  Bentonite is formed by chemical and mechanicalprocess of rock which is influenced by weather (on the alkaline environment). < 1 - -Glimer cation which bound with 6 hydroxyl ion(OH 3+ cation which bound with 4 oxygen atom. While octahedral layer consists of Al 4+ According to Bergaya (2006), Montmorillonite (Mt) that is found in bentonite consists of 2 two tetrahedral layerand one octahedral layer.

2.7. Chemical Structure of Montmorolinite

  Figure 2. Chemical structure of Montmorollonite 3 2 O 7.2 % 7.22 % H 2 O 0.4 % 0.55 % K 2 O 2.2 % 0.50 % MgO 1.3 % 3.30 %Na 3.9 % 5.30 %CaO 0.6 % 3.68 % 2 O (Source: Li 1995) 19.8 % 17.33 %Fe 3 2 O Al 2 61.3 – 61.4 % 62,12 % SiO Table 2.

2.8. Autogenous Healing Concrete using Geomaterial

  A comparison X-Ray mapping between self healing zone and original zoneSource: Ahn and Kishi (2009) According to Ahn and Kishi (2009), alkaline activator 2 of geomaterial A in presence of Ca(OH) which is resulted from hydration reaction led to form amorphous CalciumAluminosilikat gell, which have same characteristics with Figure 2.8 geopolimer gell in high alkaline environment. The self healing process in term of cracks width is analyzed by  index which iscalculated based on ratio between decreasing of crack width at time t and the initial crack width.

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 hydraulicproperties. 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.

I). This fact is contributed by amount of Ca (OH)

  As the composition of a CEM III cement is similar to the composition of the mixture where 85% of the cementweight is replaced by blast furnace slag, it can be expected that both heat production curves follow the same coursewhich is also observed Figure 2. 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 Figure 2.21, closure rate.

CHAPTER II I 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.

3.1. Literature Riview

  Spesific gravity of fine material is defined as the ratio of its particle weight to thetotal volume of particles. Fill the empty pycometer with kerosene until volume capacity marking of pycnometer and thenmeasure weight of pycometer + kerosene and record the weight (C).

3.3.2. Method to Determine Density

  Determine the mass of the measure and sample content (A), and the measure alone (B), and thenrecord to nearest 5 gram. Calculate value of unit weight using equation in poin c and the calibration factor Shoveling Procedure 6 Fill the measure to overflowing by means of shovel or scoop discharging the materials samplesfrom 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 thenrecord 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 3procedure include rodding, jigging and shoveling procedure. Density for each procedure is calculatedbase on following formula: ………..………..

3.3.3. Method to determine SAI

  [ 5 ] Where: sat w : Total saturated water cotent (%) 3  w: Density of water, 1 gram/cm 3 d  : Dry density of sample (gram/cm )Gs : Spesific gravity of sampleWeigh water according to saturated water content 3.of each testing material and hydrated lime material. Each layer should be scarified to a depth of 6 mm before thenext layer is compacted in order to assure a good bond between the layers.

a. Apparatus 1

  Cut off the mortar to a plane surface flush with the top of the mold by drawing the straightedgeor the edge of the trowel with a sawing motion across the top of the mold. Wipe, clean and dry the table top, and remove carefully any water from around the edge of theflow mold.

8. Mesure the diamater of the cement paste above flow table, and record the result

  Measuring flow diamater of cement paste The flow is defined as average of minimum 2 diamater from different point measurement ofdiameter. The flow is calculated based on following equation : ......…………..……...

3.3.5. Particles Size Analyze

  Thisfour series are set up to analyze influence of bentonite, blast furnace slag, and combination both of them to the selfhealing ability of cement paste, and compare to normal cement paste (B0S0). Specimens Series For each series, 3 kinds of specimens are employed, dogbone/briquet specimen is analysed for direct tensileregain and visual crack closure, cracked prisms 10 cm x 10 cm x 40 cm is used to quantify visual crack closure, depth ofcrack, and flexural regain, and cylinder specimens with dimension 10 cm in diameter and 8 cm in thickness.

3.5.3. Cylinder Specimens

  Detail specification of specimens are shown in Figure 3.8. Then, specimens were put in pipe and put waterprof on top and bottom ofcylinder specimen only put on circumference line of cylinder specimen ( see Fig. 3.9.(b) ).

3.6. Specimens Casting

  Specimen used in this research is cement paste incoporating some material such as bentonite and BFS aspartial cement replacement. Procedure for specimen casting is described as follow: 2.

b. Procedures

  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 minutesuntil the mixtures homogen. 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 beam10 x 10 x 40.

3.7. Curing Condition

  All of the specimens were cured in wet curing condition until introducing artificial crack. 1 day before introducing artificial crack on 28 agedays after casting, specimens were removed from wet curing condition, and then dried by using air condition.

3.8. Introducing Artificial Crack

  Water Imersion Curing After all of specimens have been cracked, then the all of specimens are cured again by immersing specimens inwater. Self Healing Evaluation Five kinds of testing and measurement are carried out to evaluate self healing behavior of the cement pastespecimens, including ultrasonic pulse velocity testing, microscopic investigation, direst tensile testing, andflexural testing.

3.10.1. Ultrasonic Pulse Velocity Testing

  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 ). Second measurement poin is measured 10 cm from crack lineposition, both for transmitter poin in the right side of crack line position and receiver poinin the left side of crack line position.

3.10.2. Microscopic Investigation

  measurements were perfomed after 0, 3, 7, 28, 56 days after introducing artificial crack. The methodsto determine healing efficiency index are described as follow: 1.

b. Investigation Procedure

  Specimens are put under of camera, and make sure that surface of specimen forinvestigation is clean and in dry condition. [ 9 ] A : The area covered by initial crack width (The area under L(0) line)A t : The area covered by crack width after ceratain healing time (The areaunder L(T) line) A -A t : The difference in area between these two as highlighted bydiagonal line shown in figure 3.8 Figure 3.

d. Measuring crack width

  Show the crack width result of 10 measurement by using measurementproperties button. Crack width of one observation point is average from 10 measurement of crack widthresult as shown in Fig.

e. Measuring Crack Area

  22 Determine crack position 2. Draw poligon line in the certain crack point by using poligon menu button indinolight software Figure 3.

3.10.3. Four Point Bending Test

  This test is conducted to determine the self healing properties of each series in term of flexuralstrength regain. Apparatus and testing procedure is described as follow: 1.

b. Procedure

  Rate of Increase in Net DeflectionBeam 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/min150 by 150 0.035 tp 0.10 0.05 to 0.30 by 500 mm mm/min mm/min 4. [ 10 ]Where: f : the strength, MPa P : the load, N L : the span length, mmb : 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. Thistest is conducted according to CRD-C 260-01.

1. Direct tensile testing machine

  The bearing surfaces of the clips shall be clean and free of sand, and the roller bearingsshall be well oiled and maintained so as to ensure freedom of turning. Keep the stirrups supporting the clip free of accumulations, and keep the pivots in properadjustment so that the clips may swing freely on the pivots without binding in the stirrups.

5.10.5. Measuring pH of Specimens

  This test is conducted to analyze self healing process which occur for each mixtures. Phmeasurement was conducted for four mixtures, include inside specimens and inside cracks.

a. Apparatus 1. Digital balance with 0.1% in precision

  Baker glass with 50 mL in volume capacity3. pH meter 4.

b. Sample/material

  Make cement paste suspension by dissolving 100 gram cement paste powderwith 500 mL free water ion (ratio between the powder and water are 1 : 5) 1. 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 afterhealing process. Then, specimens were put in pipe and waterprof was introduced on thebottom side of cylinder specimens.

b) Specimens were submerged in NaCl solution

  To determine cloride penetration of each specimens, 4 location were choosen for cloride ionpenetration test. 4 location were choosen 2 cm, 4 cm, and 6 cm from top side for crack area, and 4cm from top side for non crack area.

5.10.7. XRD Analysis

  This XRD analysis is used to verivy the healing mechanism occurred in the specimen byidentify mineral closing crack gap. Beside that from this method, the dominant effect of selfhealing mechanism in cracked cement paste can be analyzed.


  General IntroductionIn this chapter, it will be described about testing and observation result, both for raw materials used in thisresearch and cement paste, especially for healing properties of the cement paste. Testing Result of The Raw MaterialsSome testing of raw material, such as specific gravity, density, SAI, XRD, XRF, particle size, and flow ability wereconducted to support self-healing property's data of the cement paste.

4.2.1. Spesific Gravity of Material

  Spesific Gravity Test Result of BFSTrial Unit Weight Value 1 2 Weight of Pycno + Kerosene (C) gram 524.50 562.50Weight of Pycno + Kerosene + Sample (B) gram 619.00 651.00 Weight of pycno + sample (W pm ) gram 243.00 274.20Weight 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 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. Density Test Result of OPCWeight for each procedures Trial Unit Rodding Jigging Shoveling 1 2 1 2 1 2 W chamber (B) gr 1.07 1.07 1.07 1.07 1.07 1.07chamber and sample W (A) gr 3.63 3.60 3.56 3.56 3.30 3.30W sample (A – B) gr 2.57 2.54 2.49 2.49 2.24 2.233 V chamber (V) cm 2.00 2.00 2.00 2.00 2.00 2.00 Dry density for each3 gr/cm 1.28 1.27 1.25 1.24 1.12 1.12procedure ([A-B]/V) Dry density for each3 gr/cm 1.28 1.25 1.12 procedure3 Dry density gr/cm 1.21 Table 4.

4.2.3. Strenght Activity Index

  SAI Test Result of Some Raw MaterialsMaterial SAI Cov Fc on 7 age days (Mpa) Average (Mpa) 1 2 3 OPC 22.92 25.47 23.43 23.94 1.00 1.55 %Bentonite 3.85 3.74 3.74 3.78 0.16 1.59 % BFS 17.83 17.83 16.8117.49 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. According to SNI 03 – 6815 – 2002, varians coefficient of testing in the laboratory isclassified into five parts, that are excellent, very good, good, enough, less with the varians coefficients in range of0 – 3.0, 2.0 – 3.0, 3.0 – 4.0, 4.0 – 5.0, and greater than 5.0 respectively.

0.73. This value is smaller than OPC but greater than Bentonite. This fact is inline with XRD result in Fig. 4.3.

  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 latent hydraulic reaction. 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.

4.11. Ca-Bentonite used in this research contains Quartz

  Since the Montmorillonitecontent in bentonite increase, it will be followed by incrrease in swelling capacity of bentonite. Because of the amount of Montmorillonite in Ca Bentonite 9,21% (Table 4.11), thus the swelling capacityis smaller than Na Bentonite used by Kishi (2009) with montmorillonite content almost 76%.

4.2.5. XRF

  Chemical Compound of BentoniteNo Parameter Unit Test Result 1 SiO 2 % weight 56,13 2 Al 2 O 3 % weight 21,57 3 Fe 2 O 3 % weight 5,31 4 K 2 O % weight 1,29 5 MgO % weight 0,95 6 TiO 2 % weight 0,87 7 CaO % weight 0,58 8 Na 2 O % weight 0,23 9 Cr 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 inBentonite are SiO 2 , Al 2 O 3 , and Fe 2 O 3 with precentage56.13% , 21.57% , and 5.31% respectively. 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 withprecentage vaeried between 60% – 66%, 19% – 25%, 3% – 8 % , 1% – 5% , and 4% respectively.

2 O) are limited ,5% max and (0.60% – 0.90%)

2 O + 0.658 K

  Based on XRF result in Table 4.8, the amount of sulfida oxide is 0.45 %. The total amount of totalalkalies oxide in BFS is calculated according to ASTM C989-05 as follow : 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%.

ASTM C989-05

4.2.6. Particles Size Distribution

  It means that almost 7,42% of the BFS particle belongs to fineaggregat, because the particle diameter is greather than 75 µm and smaller than 4,78 mm (maximum diameter is 125µm). Based on the PSA result of Bentonite and BFS, the amount of BFS particle passing 75 µm is gretaher thanbentonite.

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. Specificsurface area is defined as total surface area of particle, which has correalation with reactivity properties As wideas Spesific surface area of powder material, it will be followed by increasing reactivity of the powder material.


  2 57.70 2881.26 2933.79 61.30 2969.783 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 2and Bentonite are 2933.79 cm /gram and 1996.17 2cm /gram respectively. Based on particle size data, the amount of BFS particle passing 75 µm is gretaher than bentonite.

4.2.8. Flowability of The Cement Paste Mixture

  The floawability was measured by determining average of minimum 2 diameter of the cement pastemixture on the flow table after the table is dropped 25 times in 15 s. Flowability of the cement paste mixtureUtilization of bentonite and BFS as partial cement replacement can decrease flowability of the cementmixture with contant water/binder ratio.

4.3. Testing Result of Self Healing Evaluation

4.3.1. Crack Width

  The objective of this process is to obtain microscopic pictures of the crackevolution over time, the decreasing crack width over time, and the β index over time for each mixture. Theseparameter are used to evaluate self healing process, where β index is healing effectiveness of cement paste mixturesover 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 thespeciment at the time 0 and t days respectively after introducing artificial crack.

1.67 Si

  However, it has difference in rate of healingefficiency, where rate of healing for the large initial crack width is lower than small initial crack width. But this result is very excited, that maximum crack width could heal completely bycontinued hydration of BFS is greather than the maximum crack width reported by Edvardsen (1999) and Li et al (2007).

4.3.2. Crack Depth

  Crack depth also is used to evaluate self healing process, and to ensure that self healing process is not onlyoccur in the surface of crack, but also occur inside of the crack. 24 Decrease in crack depth over time for each mixturesBased 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 pulsevelocity.

4.3.3. Direct Tensile Regain

  Each specimen was subjected to the direct tensile test on 28age days after casting to introduce artificial crack and to determine tensile strength properties for each mixture on28 age days after casting. After 56 age curing period, specimens were removed from specimen holder andsubjected to the direct tensile test again to proof that self- healing process occur, in terms of tensile regain.

B0FS30 B0FS00 B5FS30

B5FS00 15492

  This iscaused by the bentonite was dominated by crystalline mineral and the reactivity of Bentonite is very low (0.15), as explainedin reactivity test result and XRD result. It is noticedthat tensile strength of B0S30 and B5S30 are higher than tensile strength of B0F0 and B5S0 respectively.

4.3.4. Flexural Recovery

  Flexural stifness before (B) and after (A)healing process for different mixtures Self-healing process in terms of flexuralstiffness regains of some mixtures are shown in Figure 4.36. It has been shown by crack depth measurement that the maximumrates of healing of all mixtures are around 0.35, in terms of crack depth.

4.3.5. Alkalinity

  Ph of the specimens inside the crack was lower than insidespecimens. Ph of the cement paste was influenced 2+significantly by Ca ion, which is come from Ca((OH) 2 .

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