This document presents a study on the effect of different molarity of alkaline activator on fly ash based concrete. It includes an introduction to geopolymer concrete and its benefits over ordinary Portland cement concrete. The objectives are to study the compressive and tensile strengths of geopolymer concrete with alkaline activators of 8M, 10M and 12M molarity. The results show that both compressive and tensile strengths increase with curing age and molarity. Geopolymer concrete with 12M alkaline activator achieved the highest strengths. The conclusion is that fly ash concrete can replace cement while achieving similar or better strengths through the geopolymerization process.

1. EFFECT OF DIFFERENT MOLARITY OF
ALKALINE ACTIVATOR ON FLY ASH BASED
CONCRETE
(SUBMITTED AS A PARTIAL REQUIREMENT FOR THE DEGREE OF MTECH
IN CIVIL ENGINEERING)
Submitted By: Under the guidance of :
Umesh Chakraborty (1411029) Prof. Sunny Jaiswal
Reg No. 14281835110
SCHOOL OF CIVIL ENGINEERING
KIIT DEEMED TO BE UNIVERSITY

2. CONTENTS
 INTRODUCTION
 LITERATURE REVIEW
 OBJECTIVES
 METHOD AND PROCESS
 RESULTS
 CONCLUSION
 REFERRENCE

3. INTRODUCTION
 Cement is the typical binder material used for manufacturing
concrete.
 The production of cement produces a total of 21% of CO2 of the
total global carbon emission from various industries.. For every
1000kg of cement produced, CO2 produced is nearly 927 kg.
 Globally, concrete production and usage is increasing at a rate of
5% annually.
 India alone produced 502 mtpy in 2018, which is estimated to reach
550 mtpy by year 2020.
 This instigates the requirement of usage of material that would
replace cement while retaining similar properties but reduce
environmental degradation.

4. GEOPOLYMER
 Geopolymer is an amorphous
alkali alumino-silicate substance
activated by alkali base materials.
 Geopolymer concrete can be
produced by polymerizing the
Alumino-silicates present in Fly
ash(FA), Metakaolin (MK),
Slag(SG), Rice husk ash(RHA),
Ground granulated blast furnace
slag(GGBS) with alkaline
activators such as sodium
hydroxide/sodium silicate.
GGBS

5. SALIENT FEATURES OF GEO-POLYMER
CONCRETE:
 GPC is ecofriendly concrete.
 In geopolymer concrete, partial to 0 % OPC
is used, thus reducing the emission of CO2.
 Curing of geopolymer concrete can be done
in an oven at a certain temperature, thus
reducing the usage of water.
 The mechanical properties of certain
Geopolymer concrete are advanced than
nominal concrete.
Rice husk
ash

6. Geopolymers are manufactured from
industrial wastes. The most used are:
Fly ash: it is the by-product
from thermal or coal industry.
GGBS: it is the residual waste
from iron and steel industry.
Being industrial by-products, they are
treated such that the pollutants present
in them is reduced, as well as price is
lower than to Ordinary Cement.
Fly ash

7. - When mixed with alkali
activators, they show binding
properties similar to OC.
- Curing temperature of
Geopolymer is 60-70⁰C, while
OPC can be cured at normal
temperature in the presence of
abundant/excessive water.
- Durability property of
Geopolymer concrete mix is
higher than the nominal
concrete mix.

8. S No. AUTHOR YEAR SUMMARY
1 Dr. C. Antony
Jeyasehar et al.
(2013) Studied the polluting effect
of conventional cement
and the CO2 emission from
cement manufacturing
2 Mohammed Asim
Ahmed et al.
(2017) Studied the different alkali
activators and their effect
on geopolymer concrete
LITERATURE REVIEW

9. S No AUTHOR YEAR SUMMARY
3 Nguyen et al. (2015) Studied and gave a
report of the physical
properties of
geopolymeric binders.
4 Shankaraiah
Srinivas et al.
(2017) Studied the nature of
alkali activators and
reported the optimal
activator is NaOH and
Na2SiO3

10. S No AUTHOR YEAR SUMMARY
5 A.M. Izzat et al. (2011) Studied the chemical
properties and the
reactions taking place in
the process of
polymerisation of GPC
6 P Visintin et al. (2017) Compared the durability
evaluation of OCC and
GPC.
7 Ali & Abdullah (2014) Studied the effect of
admixture and reported
that 0.8-1.5% results in
best GPC

11. OBJECTIVE
 Cast OCC of grade M25 and record the compressive
strength and tensile strength to be used as reference.
 Cast GPC at different molarity of activator solution
and study the compressive strength and tensile
strength.
 Compare the test results of OCC and GPC, and
determine the proficiency and usability of GPC over
OCC.
 Study the change in strength at different ages of the
concrete moulds.

12. METHODS AND PROCESS
 Alkaline activator solution induces the Si and Al atoms in
Geopolymers to react.
 The application of heat, assists in the formation of gel.
 The gel formed binds all the ingredients together to form
the concrete.
 Applying heat during the process of curing helps in the
polymerisation of the concrete mix.
 Different chemicals can be used to prepare the solution,
but prior studies have shown that sodium hydroxide
(NaOH) and sodium silicate(Na2SiO3) gave the best
result.

13. REACTIONS TAKING PLACE DURING
POLYMERISATION
 The Si and Al present in fly ash reacts with the activator solution.
Al2O3+3H2O+2OH- 2[Al(OH)4]-
SiO2+H2O+OH- [SiO2(OH)2]2-
The total reaction occurring is:
2SiO2Al2O3+3OH-+3H2O 2[Al(OH)4]- + [SiO2(OH)2]2-
The final chemical structure of fly ash based cement is:
HO O
HO Al O Si OH
HO O

14. MOLARITY
 Molarity is the number of moles of solute (the material
dissolved) per litre of solution.
- To prepare 1 molar solution of NaOH, molar mass of
NaOH is needed which is 40 grams (23 for Na, 16 for O,
and 1 for H), then dissolve these 40 grams of solid NaOH in
solvent such that total volume of final solution is one litre.
M = no.of moles
liters of solution
 Geopolymer concrete moulds of alkaline solution of
molarities 8, 10 and 12 will be prepared.

15. ADMIXTURE
 Admixtures are additives which provide special properties to fresh
or hardened concrete. Admixtures may enhance the durability,
workability or strength characteristics of a given concrete mixture.
 The most often used admixtures are air-entraining agents, water
reducers, water-reducing retarders ,accelerators and SPs.
 The admixture Super plasticizer (MasterGlenium SKY 8233) was
added to the concrete mix at 0.8-1.5% to improve the quality of the
concrete mould.
 The addition of SPs reduce the water requirement by 12-30%.
 Since admixtures enhances the workability of the mortar, the
amount of admixtures and water must be calculated accordingly,
otherwise after a certain point, the strength will be decreased.

16. Sodium
silicate
Sodium
hydroxide
Water
required
precursor
Fly ash
Aggregate
(fine+coarse)
Solid mix
Geopolymer
concrete

17. SPECIFIC GRAVITY
SPECIFIC GRAVITY VALUE
CEMENT 3.15
FA
(Size= 4.75mm)
2.64
CA
(Size=20mm) 2.84
FLY ASH 2.31

18. PROCESS OF PREPARATION OF GPC MOULDS
 AAS content was fixed at 200 kg/m3. GPC developed using this AAS was
found to be effective with better strength, workability and economy.
 Using AAS/FA ratio 0.5, FA was found to be 400 kg/m3.
 Ratio of Na2SiO3 and NaOH employed was 1.5.
 NaOH to be used is 80 kg/m3 and Na2SiO3 is 120 kg/m3
 Total Water Content in the mix was calculated to be 122.2kg/m3
 Total Aggregates to be used is 0.654 m3.
 From that mass of fine aggregate was calculated 619kg/m3.
 Coarse aggregate used were: 10mm, 20mm.

19.  Total Coarse Aggregate = 1148.91kg/m3
 Using cube mould of 150*150*150mm, and cylindrical mould of 150mm
diameter, 300mm length for the tests, the values of different materials were
found to be:
COMPONENTS VALUES
(Kg)
BINDER CONTENT
(FLY ASH)
6.96
NaOH 1.392
Na2SiO3 2.088
WATER 2.13
COARSE AGGREGATE 14.69
FINE AGGREGATE 6.99

20. RESULTS
COMPRESSIVE STRENGTH OF CUBES
DAYS MOLARITY
OCC 8M 10M 12M
7 27.08 25.55 28.26 29.60
14 29.98 26.23 29.35 32.21
28 32.06 27.05 30.32 36.31

21. COMPRESSIVE STRENGTH FOR 7 DAYS
0
5
10
15
20
25
30
35
OCC 8M 10M 12M
COMPRESSIVESTRENGTH(MPa)
COMPRESSIVE STRENGTH AT 7 DAYS

22. 14 DAYS ANALYSIS
0
5
10
15
20
25
30
35
OCC 8M 10M 12M
COMPRESSIVESTRENGTH(MPa)
COMPRESSIVE STRENGTH AT 14 DAYS

23. 28 DAYS ANALYSIS
0
5
10
15
20
25
30
35
40
OCC 8M 10M 12M
COMPRESSIVESTRENGTH(MPa)
COMPRESSIVE STRENGTH AT 28 DAYS

24. COMPRESSIVE STRENGTH COMPARISON
7 DAYS 14 DAYS 28 DAYS
OCC 27.08 29.98 32.06
8M 25.55 26.23 27.05
10M 28.26 29.35 30.32
12M 29.6 32.21 36.31
0
5
10
15
20
25
30
35
40
COMPRESSIVESTRENGTH(MPa)
COMPRESSIVE STRENGTH

25. COMPARISON OF COMPRESSIVE STRENGTH ON
THE BASIS OF MOLARITY
25.55 26.23
27.05
28.26
29.35
30.3229.6
32.21
36.31
0
5
10
15
20
25
30
35
40
7 DAYS 14 DAYS 28 DAYS
CHANGE IN CS DUE TO DIFFERENT MOLARITY
8M
10M
12M

26. SPLIT TENSILE STRENGTH OF CYLINDRICAL
MOULDS
DAYS MOLARITY
OCC 8M 10M 12M
7 2.45 3.18 3.54 3.84
14 3.17 3.27 3.59 4.18
28 3.53 3.38 3.80 4.71

27. 7 DAYS ANALYSIS
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
OCC 8M 10M 12M
TENSILELOAD SPLIT TENSILE LOAD AT 7 DAYS

28. 14 DAYS ANALYSIS
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
OCC 8M 10M 12M
TENSILELOAD SPLIT TENSILE LOAD AT 14 DAYS

29. 28 DAYS ANALYSIS
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
OCC 8M 10M 12M
TENSILELOAD SPLIT TENSILE LOAD AT 28 DAYS

30. OVERALL COMPARISON OF SPLIT TENSILE
STRENGTH
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
7 DAYS 14 DAYS 28 DAYS
OCC
8M
10M
12M

31. COMPARISON OF SPLIT TENSILE
STRENGTH ON THE BASIS OF MOLARITY
3.18 3.27
3.38
3.54 3.59
3.83.84
4.18
4.71
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
7 DAYS 14 DAYS 28 DAYS
CHANGE IN SPLIT TENSILE STRENGTH DUE TO
DIFFERENT MOLARITY
8M
10M
12M

32. CONCLUSION
 Compressive strength of flyash concrete at 8M, 10M and 12M alkaline
activator solution increases compared to ordinary concrete. However it
is observed that compressive strength increases with increment in
molarity.
 The split tensile strength also increases with age and molarity. It is
observed that with increase in molarity the strength increases.
 Hence, there is window of opportunity to replace cement with flyash
for preparing concrete for construction purpose.
 It was found that the range of admixture to be added is 0.8-1.2%,
which was previously quoted at 0.8-1.5%. The increase in the amount
of admixture increases the workability, which factors in the loss of
strength.

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35. Thank you