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![Material Used
Test Details Test Results Requirement as per IS
3812: 2003 [3]
Colour Light grey -
Specific Surface Area 416.4 m2/kg Min. 320 m2/ kg
Loss of ignition 1.1 % Max. 5 % by mass
SiO2 + Al2O3 + Fe2O3 93.0 % Min. 70 % by mass
SiO2 61.4 % Min. 35 % by mass
Reactive Silica 34.7 % Min. 20 % by mass
CaO < 5%
MgO 1.4 % Max. 5 % by mass
SO3 0.6 % Max. 3 % by mass
Na2O 0.6 % Max.1.5 % by mass
Total Chlorides 0.03 % Max. 0.05 % by mass
Retention on 45
micron sieve
21.1 % Max. 34 % by mass
Pozzolanic Activity
Index
88.2 % Min. 80 % by mass
Test Details Test Results
Colour White
Specific
Surface Area
379 m2/kg
Loss of
ignition
0.6 %
SiO2 36.8 %
Al2O3 10.1 %
CaO 37.0 %
Fe2O3 0.6 %
Glass Content 92.5 %
Retention on
45 micron
sieve
11.0 %
Pozzolanic
Activity Index
90.9 %
Table 1 Chemical Composition of Fly ash Table 2 Chemical Composition of Slag](https://image.slidesharecdn.com/mixturedesignofflyashslagbasedalkaliactivatedconcreteforprecastconcrete-171128070324/75/MIXTURE-DESIGN-OF-FLY-ASH-SLAG-BASED-ALKALI-ACTIVATED-CONCRETE-FOR-PRECAST-CONCRETE-4-2048.jpg)
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MIXTURE DESIGN OF FLY ASH & SLAG BASED ALKALI ACTIVATED CONCRETE FOR PRECAST CONCRETE
The document discusses the design and evaluation of alkali activated concrete using fly ash and slag, focusing on the parameters that affect its compressive strength. Key factors analyzed include the amounts of source materials, molarity of sodium hydroxide, alkaline ratios, superplasticizer dosage, and the impact of extra water. The findings indicate that optimizing these parameters can enhance compressive strength, with results showing a potential strength of approximately 30 MPa after 24-hour oven curing.
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MIXTURE DESIGN OF FLY ASH & SLAG BASED ALKALI ACTIVATED CONCRETE FOR PRECAST CONCRETE
- 1. MIXTURE DESIGN OFFLY ASH & SLAG BASED ALKALI ACTIVATED CONCRETE FOR PRECAST CONCRETE Department of Civil Engineering Institute of Technology Nirma University Prepared By: Prof. Sonal P Thakkar Assistant Professor Daxesh Patel M.Tech Student 33rd National Convention of Civil Engineers, IEI
- 2. Introduction • Davidovits proposedthat an alkaline liquid which can react with the silicon (Si ) and aluminum (Al) in a source material of geological origin or in by product material can be used to produce binders. • Alkali activated concrete constitutes of two main compounds namely source materials and alkaline liquids. Source materials are materials like fly ash, granulated blast furnace slag, rice husk ash, silica fume, red mud, etc. • The alkaline liquids are from soluble alkali metals which are sodium or potassium based. Sodium hydroxide (NaOH) or Potassium Hydroxide (KOH) and Sodium silicate or Potassium silicate are most widely used alkaline liquid.
- 3. Introduction(continued……) • Present investigationattempts to find parameters affecting strength of alkali activated concrete using fly ash and slag as source material. High compressive strength in early period makes it ideal material for precast work in construction industry as it has controlled environment and excellent quality control.
- 4. Material Used Test DetailsTest Results Requirement as per IS 3812: 2003 [3] Colour Light grey - Specific Surface Area 416.4 m2/kg Min. 320 m2/ kg Loss of ignition 1.1 % Max. 5 % by mass SiO2 + Al2O3 + Fe2O3 93.0 % Min. 70 % by mass SiO2 61.4 % Min. 35 % by mass Reactive Silica 34.7 % Min. 20 % by mass CaO < 5% MgO 1.4 % Max. 5 % by mass SO3 0.6 % Max. 3 % by mass Na2O 0.6 % Max.1.5 % by mass Total Chlorides 0.03 % Max. 0.05 % by mass Retention on 45 micron sieve 21.1 % Max. 34 % by mass Pozzolanic Activity Index 88.2 % Min. 80 % by mass Test Details Test Results Colour White Specific Surface Area 379 m2/kg Loss of ignition 0.6 % SiO2 36.8 % Al2O3 10.1 % CaO 37.0 % Fe2O3 0.6 % Glass Content 92.5 % Retention on 45 micron sieve 11.0 % Pozzolanic Activity Index 90.9 % Table 1 Chemical Composition of Fly ash Table 2 Chemical Composition of Slag
- 5. • To increasethe workability of fresh concrete, naphthalene based superplasticizer, Rheobuild was used. Figure 1 Image of NaOH flakes Figure 2 Image of Na2SiO3
- 6. Mixture Design ofAlkali Activated Concrete with Flyash and Slag • In order to evaluate parameters affecting the compressive strength, density of concrete was assumed to be 2400 kg/m3 and variation was done in following parameters: Amount of source material Molarity of sodium hydroxide Ratio of sodium hydroxide to sodium silicate Super plasticizer Dosage Extra water
- 7. Effect of CombinationOf Source Material Table 3 Variation of source material Mix No. GGBS % Fly ash % Mix 1 10 90 Mix 2 20 80 Mix 3 30 70 Mix 4 40 60 Mix 5 50 50 Mix 6 60 40 • For this particular variation following data is considered: Ratio of alkaline liquid to fly ash and GGBS 0.4 Ratio of sodium silicate to sodium hydroxide 2.5 Concentration of sodium hydroxide solution 12M Admixture dosage 1.5% Curing temperature 90 ℃ Curing time 24 hours
- 8. Figure 3 Comparisonof compressive strength (N/mm2) for different mixture proportions 4.5 7.9 9.4 16.2 27 14.2 6.4 11.1 16.4 20.9 31 30.2 0 5 10 15 20 25 30 35 Mix 1 Mix 2 Mix 3 Mix 4 Mix 5 Mix 6 CompressiveStrength Comparison of compressive strength (N/mm2) for different mixture proportions 7th Day Compressive Strength 28th Day Compressive Strength
- 9. Effect of CombinationOf Source Material (Continued…) • It can be observed that with increase in slag content, compressive strength also increases when curing temperature was 90°C for 24 hours. • Higher percentage of slag content lead to decrease in workability and hence mixing became difficulty, therefore equal proportion of slag and fly ash was considered for further studies. Also it can be observed that at equal percentage of source material at 7 days the required compressive strength was obtained.
- 10. Effect of Molarityof Sodium Hydroxide Figure 4 Comparison of compressive strength(N/mm2) for different molarity 9.63 16.44 24.74 13.8 21 28.89 0 5 10 15 20 25 30 35 3 day 7 day 28 day CompressiveStrength Curing Time Compressive Strength(N/mm2) comparison for 24 hour oven cured samples 10 M 12 M
- 11. Effect of Molarityof Sodium Hydroxide (continued…..) • Two molarities 12 M and 10 M were taken to study the effect on compressive strength. Figure 1 shows effect of molarity on compressive strength when curing was done for 24 hours in oven. • Increase in molarity will lead to addition of more amount of sodium hydroxide quantity which will lead to having more amount of alkaline activator to react with cementitious material. • It can be observed that with increase in molarity from 10 M to 12 M compressive strength increases to 29 MPa from 25 MPa at 28 days.
- 12. Effect of AlkalineRatio Figure 5 Comparison of compressive strength(N/mm2) for different alkaline ratio 13.8 21 28.89 15.5 20.89 29.78 0 5 10 15 20 25 30 35 3 day 7 day 28 day CompressiveStrength(N/mm2) Curing Period 24 hours Oven Cured Ratio 2 Ratio 2.5
- 13. Effect of AlkalineRatio (continued…..) • Alkaline ratio of sodium silicate to sodium hydroxide was varied as 2.0 and 2.5 and specimen were subjected to one day oven curing as shown in Figure 2. • It was observed that there is slight increase in compressive strength with increase in alkaline ratio.
- 14. Effect of SuperplasticizerDosage Figure 6 Comparison of compressive strength(N/mm2) for different dosage of superplasticizer 13.8 21 28.89 16.9 25.3 32.44 0 10 20 30 40 3 day 7 day 28 day CompressiveStrength Curing Period Compressive Strength(N/mm2) comparison for diiferent dosage of superplasticizer 1% 1.50%
- 15. Effect of SuperplasticizerDosage (Continued…..) • Two different dosage of plasticizer of 1% and 1.5% was taken to evaluate it’s effect on compressive strength. As seen in figure 3, with increase in dosage of superplasticizer, compressive strength also increases, but it was observed that beyond 2% dosage of superplasticizer lead to decrease in compressive strength. Also increase in super plasticizer will lead to increase in cost and hence its dosage is restricted.
- 16. Effect of ExtraWater 15.1 23.9 30.96 17.3 25.19 32.15 0 5 10 15 20 25 30 35 3 day 7 day 28 day CompressiveStrength Curing Period 10% extra water added Extra Water Content 24h 48h Figure 7 Comparison of compressive strength for 10% extra water for 24 and 48 hours
- 17. Effect of ExtraWater (continued…..) • In order to increase workability of concrete, extra water was added. Similar to water cement ratio, addition of more water in concrete will lead to decrease in compressive strength. • Lesser addition of water leads to difficulty in compacting and thereby decreases strength. As workability increases with extra water, increase in compressive strength to a certain extent was achieved.
- 18. Conclusion • It canbe concluded that when oven curing for 24 hours was done approximately strength of 30 MPa could be achieved and approximately 25 MPa to 27 MPa strength could be achieved at 7 days depending upon parameters of mix design. • Also increase in molarity and alkaline solution ratio leads to increase in compressive strength. • Increase in dosage of super plasticizer and water content has direct effect on workability parameter and hence strength increases.
- 19.
- 20. References: • Malhotra V.M.(2002) ,“ Introduction: Sustainable development and concrete technology”, ACI Concrete International, 24(7). • Davidovits J.,(1994),“ Properties of geopolymer cements”, First international conference on alkaline cement and concretes, Ukrain, page:131-149. • IS: 3812 –2003, Specification for fly ash for use as pozzolana and admixture, Bureau of Indian standards, New Delhi. • IS: 383-1970, Specification for coarse and fine aggregate from natural sources of concrete Bureau of Indian Standards, New Delhi • Hardjito D., Rangan B.V.(2005)“ Development and properties of low- calcium fly ash based geopolymer concrete”, Research Report GC1, Faculty of engineering, Curtain University, Perth, Australia.
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