© 2019 JETIR February 2019, Volume 6, Issue 2 www.jetir.org (ISSN-2349-5162)

JETIRAB06130 Journal of Emerging Technologies and Innovative Research (JETIR) www.jetir.org 688

Effect of Concentration of Sodium Hydroxide

Solution on

Compressive Strength of Geopolymer Concrete

Ravi Sanker Reddy .Battu 1, Dr.D.V.Prasada Rao2

[1]Research Scholar, Civil Engineering Department, S.V.University College Of Engineering, Tirupati, India, [2] Professor,Civil Engineering Department, S.V.University College Of Engineering, Tirupati, India

[1] batturaviii@gmail.com, [2] dvpr@rediffmail.com

Abstract— This paper contains results of the tests carried out to find the effect of different concentrations of sodium hydroxide

solution on the strength of the geo-polymer concrete. Now a days, a big problem facing by the world is carbon dioxide. The

production of Ordinary Portland cement causes emission of Co2 which leads to environmental pollution. Supplementary material like fly ash can be used in place of ordinary Portland cement to reduce Co2. The Concrete made by activation of Fly ash with

highly alkaline liquids is known as geo-polymer concrete. The alternative material which is sustainable and eco-friendly to Portland cement concrete is Geo-polymer concrete (GPC). Highly alkaline liquids like Sodium Hydroxide (NaOH) and Sodium

Silicate (Na2SiO3) are used in this investigation for the polymerization process. Different concentrations of sodium hydroxide solution i.e. 8M, 10M, 12M, 14M and 16M were taken in preparing different GPC mixes and the compressive strength of each mix

were obtained .The size of specimen used for testing is 100mm X 100mm X 100mm.Oven curing was adopted in this investigation and cubes are kept in an oven for 1 day,3 days,7 days and 28 days and then GPC specimens were tested for Compressive strength..

The result shows that compressive strength of GPC increases with increase in molarity of Sodium Hydroxide solution.

Index Terms— Alkaline Solution, Concentration, Fly ash, Geo-polymer concrete, Sodium hydroxide, Sodium silicate,

Molarity. INTRODUCTION

The main problem to the human beings is the environmental pollution. Adding impurities to the nature is nothing

but polluting the environment. Concrete is widely using globally next to the water. In the construction industry, Cement is

one of the major components used in the production of concrete. Production of 1 ton of cement releases nearly about 1 ton

of CO2 into the atmosphere. Burning of fossil fuels to operate the kiln and the chemical process of burning limestone

releases CO2. Cement production requires huge amount of raw materials like lime stone, clay and other minerals. One ton of

cement production requires nearly 1.6 tons of raw materials. Quarrying of raw materials also leads to lack of sustainability.

The contribution of green house gas emission from cement industry is about 7% of the total greenhouse gas emissions to the

earth’s atmosphere. Day by day demand for concrete is increasing, thereby increase in production of cement which leads to

increase in environmental pollution and global warming. The geo-polymer concrete concept was introduced by Joseph

Davidovits in 1970’s. He proposed a method in which an alkaline liquid such as sodium hydroxide or sodium silicate

solution was used to activate industrial by products like fly ash or Ground granulated blast furnace slag (GGBS) to produce

binders [1]. The green house gases like CO2 alone causes 65% of total global warming. Some of the industrial by products

like fly ash, GGBS and rice-husk ash can also be used as source material [2].

Many efforts were in progress to supplement the use of cement concrete with GPC in order to reduce the global

warming. It includes the utilization of industrial byproducts like fly ash, metakaolin, ground granulated blast furnace slag and

rice-husk ash as an alternative binder to Ordinary Portland cement. Almost all the states in India are producing fly ash

abundantly as a byproduct in their thermal power plants. Highly alkaline solutions like sodium hydroxide and sodium silicate

are cheap and easily available [3]. In this respect, the geo-polymer technology plays an important role in the application of

concrete industry. Global warming caused by the cement industries can be reduced significantly by adopting geo-polymer

concrete. Initially applications of the fly ash based geo-polymer concrete was attempted as fly ash is abundantly available.

Most of the previous studies on geo-polymer concrete are based on curing by heating. The rate of polymerization is very fast at

60oC to 90

oC temperature . Most of the states in India come under tropical region where the temperature during summer is

above 30oC. Geo-polymer concrete, which is cured naturally or at room temperature, can be treated as GPC cured at ambient

temperature [4]. Longer curing time increases the polymerization reaction, thus resulting in higher compressive strength. This

might be due to relatively fast chemical reaction process in the geo-polymer concrete [5]. Dissolution of silica and alumina

from Fly ash starts when it comes in contact with highly alkaline solution. The type and molarity of alkali solution affect the

dissolution of fly ash. Leaching of Alumina and Silica ions are high with sodium hydroxide solution than potassium hydroxide

solution [6].

.

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JETIRAB06130 Journal of Emerging Technologies and Innovative Research (JETIR) www.jetir.org 689

I. MATERIALS USED

2.1 Fly ash: - Fly ash is collected from Rayalaseema Thermal Power Plant, Kadapa, Andhra Pradesh, India.

2.2

Table 1: Fly Ash Properties

Parameters Experimental

Value in %

Silica 56.6

Aluminium Oxide 22.26

Iron Oxide 8.14

Calcium Oxide 12.14

Magnesium Oxide 1.17

2.2 Aggregates: - Coarse aggregate used was locally available. Sizes of coarse aggregates used are 20 mm and 12mm.

The Specific gravity of coarse aggregate used was 2.61 and fineness modulus was 5.41. The coarse aggregate used in this

investigation was surface dry condition. Fine aggregate used in this investigation is collected from Swarna Mukhi river, Tirupati, Andhra Pradesh, India. The

Specific gravity of fine aggregate used in this study is 2.63 and fineness modulus was 2.61. Fine aggregate used in this

study was surface dry condition.

2.3 Alkaline Solution: - Mixture of Sodium Hydroxide (NaOH) and Sodium Silicate (Na2SiO3) was used as an alkaline

activators. Sodium hydroxide used in this study was of commercial grade and is in the form of pellets collected from Astrra

Chemicals, Chennai, India. Sodium hydroxide solution was prepared by dissolving the pellets in water one day prior to the cast.

Sodium silicate solution, collected from Astrra Chemicals, Chennai, India, has the mass ratio of SiO2 to Na2O of 2.2 (SiO2 = 33%, Na2O

= 15% and water = 52%). Alkaline solution was prepared by mixing both of these solutions.

2.4 Water: - Drinking water was used in this study for making GPC. III. MIX PROPORTIONS

In this study, single grade of geo-polymer concrete with five different molarities of sodium hydroxide solution

(8M, 10M, 12M, 14 M and 16M ) were prepared. GPC was designed for characteristic cube compressive strength of 20

MPa . Activation of industrial by products like fly ash with highly alkaline solutions like sodium hydroxide solution and

sodium silicate solution needs heat curing for the formation of geo-polymer binder. The GPC specimens along with mould

were kept in oven for one day at 600C temperature. After one day of oven curing specimens were demoulded and cured in

an oven at 600C temperature for the period of 3 days, 7 days and 28 days.

Figure 1: Alkaline Solution In this paper, the compressive strength of GPC is obtained for the mixes of various concentrations of Sodium

Hydroxide (NaOH). Sodium Hydroxide is prepared with different concentrations of 10M, 12M, 14M and 16M as shown in

Table-2. The ratio of Na2Sio3 to NaOH used in this study is 2.0.

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Table 2: Weights of NaOH Pellets

Concentration Sodium Hydroxide

in gms

8M 320

10M 400

12M 480

14M 560

16M 640

3.2 Mixing, Casting and Curing:

The density of geo-polymer concrete was assumed to be 2400 Kg/m3. No code provisions are available for the mix

design of geo-polymer concrete. Other calculations are done by considering the density of concrete. The total volume

occupied by Coarse and fine aggregates was assumed to be 75%. The alkaline liquid to binder ratio was taken as 0.5.

Quantities of all ingredients were kept constant and are given in table 4 except the molarity of NaOH in the each mix. IS

code method (IS-10262(2009)) used for making of conventional concrete is also adopted to prepare GPC [7]. Fly ash and

fine aggregate are mixed in dry condition and coarse aggregate was then added to this mixture and then the alkaline solution

was added to this dry mix. The mixing was done about 4-5 minutes. After mixing, the cubes were cast in three layers and

given proper compaction by using table vibrator. Sizes of the cubes used are 100mm X 100mm X100mm. The cubes were

cured in oven at 600 C. The cubes with moulds were placed in an oven for 1 day and then demoulded and tested. Remaining

cubes were placed in an oven until testing (i.e 3 days,7 days and 28 days). The quantities of various materials used for

preparation of geo-polymer concrete is given in table 3.

Table 3: Ingredients and the Quantities of Geo-polymer Concrete

IV.RESULTS The compressive strength test was carried out on geo-polymer concrete mixes after the curing age of 1 day, 3 days, 7 days

and 28 days in compressive testing machine and compressive strength was determined [8]. The results obtained are given in

Table 4.

From experimental Results, it is concluded that the Compressive Strength of GPC is increased with increase in

concentration of sodium hydroxide solution. Also the rate of increase in Compressive Strength of GPC is very low after 3

days of curing and 90% of compressive strength was achieved at 3 days of curing. This property of earlier gaining

Table 4: Experimental Results

Grade of

Concrete Molarity

1 Day

Compressive

Strength (Mpa)

3 Days

Compressive

Strength (Mpa)

7 Days

Compressive

Strength (Mpa)

28 Days

Compressive

Strength (Mpa)

M 20

8M 9.16 17.75 19 21

10M 11.875 20.5 21.16 22.33

12M 13.25 21.33 21.83 23

14M 18.75 21.75 22.33 23.83

16M 19.18 22.16 22.83 24.33

Ingredients (Kg/m3) Quantities

Fly Ash 372

Fine Aggregate 501.5

Coarse

Aggregate

20 mm 603.9

12mm 402.6

Sodium Silicate Solution 124

Sodium Hydroxide Solution 62

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Figure 2

Figure 3

Figure 2 & 3 : Compressive Strength of M 20 Grade GPC mixes at the curing age of 1 day,3 days,7 days and 28days for

various molarities of NaOH Solution

strength allows the usage of GPC mixes in areas where earlier strength is required. It was also observed that increase in the

concentration of NaOH causing the GPC mix more viscous with rapid setting.

V. CONCLUSION

1) Compressive strength of GPC is increased with increase in the concentration of sodium hydroxide solution.

2) The rate of increase in Compressive Strength of GPC is very low after 3 days of oven curing.

3) 90% of the compressive strength of GPC was achieved in early age (i.e at 3 days of oven curing). Hence, this property

of early gaining strength allows the usage of GPC mixes in areas where earlier strength is required.

4) Increase in molarity of NaOH causes GPC mixes more viscous with rapid setting. Hence proper compaction is not

possible at high concentrations of NaOH. Hence compressive strength decreases.

Acknowledgements

The authors were gratefully acknowledge the support of Rayalaseema Thermal Power Plant and Astrra chemicals for

providing the fly ash and chemicals used in this study. The help of the concrete laboratory staff of Sri Venkateswara

University, Tirupati, India is gratefully acknowledged.

REFERENCES

[1] Shivaji S. Bidwe(2015), Effect of different molarities of Sodium Hydroxide solution on the Strength of Geo-polymer

concrete American Journal of Engineering Research (AJER), e-ISSN : 2320-0847 p-ISSN : 2320-0936 ,Volume-4,

Issue-3, pp-139-145

[2] Rangan, B.V., (2010), Fly ash based geo-polymer concrete, Proceedings of the International Workshop on

Geo-polymer Cement and Concrete, Allied Publishers Private Limited, Mumbai, India, December 2010.

[3] Rangan, B.V., (2008), Mix design and production of fly ash based geo-polymer concrete, Indian Concrete.

[4] Songpiriyakij S., (2005), Effect of temperature on compressive strength of fly ash based geo-polymer mortar,

http://www.smith-kmitnb.com/publication/NCC2_6.pdf on 20.11.2013

[5] Madheswaran C. 2013, Effect of molarity in geo-polymer concrete, International Journal Of Civil And Structural

Engineering ,Volume 4, No 2, 2013,ISSN 0976-4399 .

[6] Ubolluk Rattanasak (2009), Influence of NaOH solution on the synthesis of fly ash geo-polymer, Minerals Engineering

22 (2009) 1073–1078.

[7] IS-10262(2009), Guide lines for concrete mix design proportioning, Bureau of Indian Standards, New Delhi.

[8] IS-516(1959), Method of tests for strength of concrete, Bureau of Indian Standards, New Delhi.

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