International Journal of Engineering Science Invention Research & Development; Vol. II Issue XII, June e-issn:

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1 EFFECT OF FIBRES ON MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE P R ADIK 1,G A GUND 2,N A SHAH 3,S P DATTA 4,Y R LALAI 5 Department of Civil Engineering, MIT College Of Engineering,Savitribai Phule Pune University 1 pratikadik@gmail.com, 2 girishgund100@gmail.com, 3 niravashah1994@gmail.com, 4 rock.kartik2@gmail.com, 5 yashlalai93@gmail.com ABSTRACT- Geopolymer concrete, deemed by the researchers as the new age concrete is considered as a potential replacement for its conventional counterpart portland cement concrete. Already a lot of research work has gone into development and opportunities for Geopolymer concrete or cementless concrete as they call it. Everyone is now vary of the environmental impact of usage of cement and still it is worldwide the most broadly used constituent for almost all construction purposes. Geopolymer concrete uses pozzolans and other cementitious materials to replace completely the portland cement that is used on a large scale for producing concrete. Apart from water it uses solutions known as alkali activators to react with the source materials to form geocement through a process called geopolymerization. This geopolymer concrete has been studied vastly by many researchers in the past decade and these studies suggest that geopolymer concrete is supreme to the conventional cement concrete from the structural as well as durability point of view. But it still suffers from some major drawbacks like being weak in tension just like its conventional counterpart and also that it requires accelerated curing for its high early strength gain. In this research work of ours we have tried to study the effect of introduction of various types of fibres on the mechanical properties of geopolymer concrete. Keywords- Geopolymer Concrete, Fibre Reinforcement, Sodium Silicate, Sodium Hydroxide, Fly Ash I.INTRODUCTION Geopolymer concrete is the name given to concrete where the binder is entirely replaced by an inorganic polymer formed between a strong alkaline solution and an aluminosilicate source. The ratio and quantity of alkaline solution used can affectamongst other factors the concrete strength and curing time. Aluminosilicate sources are not limited to red-mud, fly-ash, blast furnace slag and kaolin. The variability of geopolymer binders and activators increase the difficulty of manufacturing a homogenous and universal geopolymer concrete standard. Currently, geopolymer concrete exhibits as good as, and in some areas superior engineering properties to normal concrete.carbon emissions can be significantly reduced by using aluminosilicate geopolymer binders instead of Portland cement (which releases 1 t of CO2 per tonne of production). Compared to Portland cement, fly-ash based geopolymer concrete can reduce carbon emissions by 80% which has the potential to reduce global emissions by approximately 2.1 billion tonnes a year. This is equivalent to taking two thirds of global traffic off the roads each year. Geopolymer is essentially cement free concrete. This material is being studied extensively and shows promise as a greener substitute for ordinary Portland cement concrete in some applications. Research is shifting from the chemistry domain to engineering applications and commercial production of geopolymer concrete. The project undertaken has included studies on geopolymer concrete mix design, structural behavior and durability. This project presents the results from studies on mix design development to enhance workability and strength of geopolymer concrete. The influence of factors such as, curing temperature and régime, aggregate shape, strengths, moisture content, preparation and grading, on workability and strength are presented. The report also includes brief details of some recent applications of geopolymer concrete. II.EXPERIMENTAL PROGRAMME We carried out trials on conventional as well as geopolymer concrete with same proportion of various types of fibres in the mix. The aspect ratio of fibres was also kept constant. The mix design for conventional concrete and its casting process has not been discussed in this paper as it very well known. However the mix design, preparation, casting and curing of GPC has been discussed in detail in the coming sections. A. MIX DESIGN P R ADIK,G A GUND,N A SHAH, S P DATTA and Y R LALAI ijesird, Vol. II Issue XII June 2016/745

2 For the design of geopolymer concrete generally some performance criterion are selected. Some guidelines for the design of low calcium fly ash based geopolymer concrete have been proposed.(hardjito et.al. 2005, Rangan 2008, Sumajouw 2007). The performance criteria of a geopolymer concrete mixture depend on the application. For simplicity, the compressive strength of hardened concrete and workability of fresh concrete are selected as the performance criteria. In order to meet this criteria, the alkaline liquid to fly ash ratio by mass, water to geopolymer solids by mass, the heart-curing temperature and time are selected as the parameters. To obtain a strength of 40 Mpa we designed the mix for M45 grade. The density of geopolymer concrete assuming aggregates are in Saturated Surface Dry condition is 2400kg/m 3. The combined mass of aggregates is taken as 77% of the mass of concrete ie equal to 0.77 x 2400 = 1848 kg/m 3. The aggregates were taken to match the standard grading curves used in design of portland cement and were somewhat modified by trial and error to get a uniform and workable mix. We took the ratio of coarse to fine aggregates as 1.20 and hence Fine Aggregates = 1848/(1+1.2) = 840 kg/m 3 ; and Coarse aggregates = 1008 kg/m 3. The mass of low calcium fly and alkaline liquid = = 522 kg/m 3. Using Alkaline liquid to fly ash ratio by mass as 0.35(recommended values by previous researchers range from 0.30 to 0.45), the mass of fly ash = 552/1.35 = 408 kg/m 3 and the mass of the alkaline liquid = = 144 kg/m 3. From the recommendations of the previous researchers the ratio of Sodium Silicate solution to Sodium Hydroxide solution by mass is taken as 2.5. Therefore the mass of Sodium Hydroxide solution = 144/(1+2.5) = 41 kg/m 3. Hence, mass of sodium silicate solution = = 103 kg/m 3. The alkali activator solutions used were bought from the local market. Locally available sodium silicate solution with Na2O = 13.72%, SiO2 = 34.16% and H2O = 52.12% by mass was used. The sodium hydroxide dry pellets with 97% purity were used. 8 Molar NaOH solution was prepared by adding water to the dry pellets in the laboratory. This solution comprises about 26% NaOH pellets and 74% water. To adjust the water to geopolymer solids ratio the following calculations are done: (i) In sodium silicate solution, amount of water = 103 x 52.12/100 = kg/m 3 ; and solids = kg/m 3. (ii) In 8M sodium hydroxide solution, amount of water = 41 x 74/100 = kg/m 3 ; and solids = = kg/m 3. Thus, total water = = kg/m 3 & Geopolymer solids = = kg/m 3. Hence water to geopolymer solids ratio = 84.02/ = But according to the design chart we need a water to geopolymer solids ratio of 0.19 for a compressive strength of 45Mpa. Thus the total water needed = x 0.19 = kg/m 3. Thus extra water required to be added = = 4.33 kg/m 3. From workability considerations, no loss of compressive strength resulted with use of superplasticizer upto 4% by mass of the source material. Hence, taking superplasticizer about 2% by weight of fly ash = 408 x 2/100 = 8.16 kg/m 3. B. PREPARATION OF ALKALINE SOLUTION 320 grams of dry sodium hydroxide pellets when dissolved in 1 litre of water give 8 Molar sodium hydroxide solution. The sodium hydroxide solution was prepared 24 hours prior to the casting so as to allow it to completely react with water and the reaction being exothermic in nature, releases a lot of heat. Just about 30 minutes prior to casting, sodium silicate solution was added to the sodium hydroxide solution and stirred well. Table 1- Final Mix Proportions for GPC Sr. No Materials Quantity(kg/m 3 ) 1 Course Aggregates Fine Aggregates Fly Ash M NaOH solution 41 5 Sodium Silicate solution Extra water 4.33 P R ADIK,G A GUND,N A SHAH, S P DATTA and Y R LALAI ijesird, Vol. II Issue XII June 2016/746

3 7 Super-Plasticizer 8.16 temperature of test was kept constant equal to 60 C for determining the effect of curing time on compressive strength. Fig.1-8 Molar Sodium Hydroxide solution Fig.2 Sodium Silicate Fig. 3- Effect of curing time on compressive strength (Hardjito and Rangan, 2005) C. MIXING AND CASTING PROCEDURE Initially the dry contents including the fine and coarse aggregates and the source material flyash were dry mixed for about 2-3 minutes in a mixer. After dry mixing the alkali activating solutions along with the superplasticizer were added in 2 to 3 installments and the wet mixing was carried out for about 4-5 minutes. The concrete after mixing was quite uniform and stiff and it was a bit tougher to handle compared to conventional concrete.it was then filled into the standard 150mm well oiled cube moulds in three layers and compacted 60 times per layer (as per recommendations of Hardjto et.al., 2005) using the standard 16mm dia. tamping rod. The surface was finished well with the help of a trowel and the specimens were then allowed to rest in ambient atmosphere for a period of 24 hours.after the so called 'rest period' of 24 hours we found that the concrete was still not completely set and so the specimens along the cube moulds were placed in the oven for curing. Fig.4 Geopolymer concrete cubes (bottom left) placed for curing in the oven along with the moulds D. CURING Heat curing of geopolymer concrete is generally recommended. Both curing time and temperature influence the compressive strength of geopolymer concrete. The effect of curing time is illustrated in figure 3(Hardjito and Rangan, 2005). The P R ADIK,G A GUND,N A SHAH, S P DATTA and Y R LALAI ijesird, Vol. II Issue XII June 2016/747

4 III.TESTS, RESULTS AND DISCUSSIONS Fig.5 shows comparison of compressive strength of Conventional concrete without fibres to compressive strength of Geopolymer concrete without fibres. From Fig.5, we can see that the conventional cement concrete gains strength gradually upto 28 days whereas geopolymer concrete shows high strength gain in the initial stages upto 7 days after which the strength gain is almost insignificant. We can thus see that the strength gained by geopolymer concrete in 7 days is almost equal to the 28 days strength of conventional cement concrete. Fig.5 Graph Showing comparison of Geopolymer concrete and Conventional concrete without fibre Fig.6 Graph Showing comparison of Geopolymer concrete and Conventional concrete with Polypropylene Fibres Fig.6 shows comparison of compressive strength of Conventional concrete with Polypropylene fibres to compressive strength of Geopolymer concrete with Polypropylene fibres. From Fig.6 we can conclude that there is rapid increase in strengths during 3 days to 7 days in Geopolymer Concrete and Conventional Concrete keeps on attaining the strength after 7 days where as Geopolymer Concrete slows down in attaining strength after 7 days, not much of difference is noticed in strengths of 7 days and 28 days in Geopolymer Concrete even after using Polypropylene fibres. P R ADIK,G A GUND,N A SHAH, S P DATTA and Y R LALAI ijesird, Vol. II Issue XII June 2016/748

5 Fig.8 Graph Showing comparison of Geopolymer concrete and Conventional concrete with Glass Fibres Fig.7 Graph Showing comparison of Geopolymer concrete and Conventional concrete with Steel Fibres Fig.7 shows comparison of compressive strength of Conventional Concrete with Steel fibres to compressive strength of Geopolymer concrete with Steel fibres. From Fig.7 we can conclude that there is rapid increase in strengths during 3 days to 7 days in Geopolymer Concrete and Conventional Concrete keeps on attaining the strength after 7 days where as Geopolymer Concrete slows down in attaining strength after 7 days, not much of difference is noticed in strengths of 7 days and 28 days in Geopolymer Concrete even after using Steel fibres. There is a slight difference in 7 days strengths of both concrete using Steel fibres. The 7 days strength in Conventional Concrete is slightly more than Geopolymer Concrete using Steel Fibres. Fig.8 shows comparison of compressive strength of Conventional concrete with Glass fibres to compressive strength of Geopolymer concrete with Glass fibres. Fig.8 we can conclude that there is rapid increase in strengths during 3 days to 7 days in Geopolymer Concrete and Conventional Concrete keeps on attaining the strength after 7 days where as Geopolymer Concrete slows down in attaining strength after 7 days, not much of difference is noticed in strengths of 7 days and 28 days in Geopolymer Concrete even after the use of Glass fibres. There is a slight difference in 7 days strengths of both concrete using Glass fibres. The 7 days strength in Conventional Concrete is more than Geopolymer Concrete using Glass fibres. Fig.9 shows comparison of Split Tensile Strength of Conventional concrete with various fibres at 28 days to Split Tensile Strength of Geopolymer concrete with various Fibres at 28 days. Fig.9 we can conclude that the Split Tensile Strength of Geopolymer concrete at 28 days is more as compared to Conventional Concrete. The difference between the strengths is almost constant (i.e. with less variation) in comparison of all types of fibres. It can be seen from the chart that use of steel fibres are giving considerable increase in compressive strength even in Geopolymer concrete (about 40%). P R ADIK,G A GUND,N A SHAH, S P DATTA and Y R LALAI ijesird, Vol. II Issue XII June 2016/749

6 Fig:- 9. Column Chart shows comparison of Split Tensile Strength of Conventional concrete with various fibres to Split Tensile Strength of Geopolymer concrete with various Fibres Fig.10 Graph showing effect of fibres on Compressive strength of Geopolymer concrete Fig.10 we can see the comparison of compressive strength of geopolymer concrete with different types of fibres at 3, 7 and 28 days. We can see that use of glass fibres is giving considerable increase in compressive strength compared to other fibres. Using glass fibres is leading to an increase in compressive strength by about 10%. IV.CONCLUSIONS 1. Water to geopolymer solids ratio for geopolymer concrete is analogous to water cement ratio in cement concrete and is the main parameter governing the strength of geopolymer concrete mix. 2. Geopolymer concrete is quire susceptible to climate changes (temperature and humidity especially) while carrying out the mixing process. Hence, care must be taken while experimental work, to carry out the casting at locations where there is not much variation in temperature and humidity with change in atmospheric conditions. 3. The final setting time for geopolymer concrete is quite long. Even after 24 hours of exposure to ambient atmosphere (about 27 C) it did not set completely. 4. The commonly used super-plasticizers for cement concrete (like ether based or naphthalene formaldehyde based super plasticizers) are not as effective for Geopolymer concrete. 5. The process of geopolymerization is quite faster than the hydration of cement concrete and almost total design strength of the mix is achieved in 7 days after which the gain in strength is insignificant. 6. Another very important parameter affecting the strength gain of the geopolymer concrete is the curing regime. Utmost care must be taken to keep the samples in oven for curing upto predetermined time period and temperature only. 7. The mechanical properties of cement concrete and geopolymer concrete are affected in similar manner by the use of various kinds of fibres. 8. Just like cement concrete, even geopolymer concrete is relatively weak in tension. The indirect tensile strength obtained is only about 10% of the compressive strength. A. RECOMMENDATIONS FOR FUTURE RESEARCH Many researchers call geopolymer concrete as the concrete of the new age and consider as a potential replacement for the conventional cement concrete due to its reduced environmental impact. But there are still many major limitations to implementing wide use of geopolymer concrete in practice. The main drawback is that geopolymer P R ADIK,G A GUND,N A SHAH, S P DATTA and Y R LALAI ijesird, Vol. II Issue XII June 2016/750

7 concrete requires elevated temperature for curing without which it does not set and gain strength soon enough. The challenge for the coming generation would be finding a way to eliminate this drawback so that geopolymer concrete can find an even wider application base like use for construction of buildings and other large structures rather than only road construction and repairing purposes. There are a lot of waste materials other than fly ash which posses cementitious properties and they can be put to use in creating geopolymer concrete. Also the costly alkali activator solutions may be replaced by combinations of some other chemicals to cut the cost of the concrete. Coming to the mix design aspect, many researchers have worked over the years on developing a rational mix design process for geopolymer concrete. But still the results do not resemble the actual design and still a lot of research work is needed to be carried out. In a country with a hot climate like India geopolymer concrete can be used advantageously and the most appropriate place for its application would be precasting industry. Unfortunately there is no standard code developed for Geopolymer concrete, but if encouragement is to be given for use of such eco friendly concrete, efforts will be required to put forward code of practice for design and usage of Geopolymer concrete. REFERENCES [1]. Micheal A. Nisbet, Medgar L. Marceau, Martha G. VanGeem; Environment Life Cycle Inventory of Portland Cement Concrete; Portland Cement Association, July 2002; PCA R&D Serial NO. 2137a. [2]. Djwantoro Hardjito, Steenie E. Wallah, Dody M.J. Sumajouw, B. Vijaya Rangan; On the Development of Fly Ash-Based Geopolymer Concrete; ACI Materials Journal; November- December 2004; Vol:101, NO.6, MS No [3]. N.A Lloyd and B.V.Rangan; Geopolymer concrete with Fly-ash; Second International Conference on Sustainable Construction Materials and Technologies, June 28 to June 30, 2010, Italy; ISBN [4]. Raijiwala D.B, Patil H.S; Geopolymer Concrete: A Concrete of Next Decade; Journal of Engineering and Research, January-March 2011; eissn: [5]. N.A Lloyd and B.V.Rangan; Geopolymer concrete: A review of development and opportunities; 35 th Conference on Our World in Concrete & Structures August 2010, Singapore; Article Online Id: [6]. K.A. Anuar, A.R.M. Ridzuan, S. Ismail; Strength characteristics of Geopolymer Concrete containing Recycled Concrete Aggregate; International Journal of Civil & Environmental Engineering, February 2011; [7]. D.B Rajiwala and H.S. Patil; Geopolymer Concrete : A concrete of next decade; Journal of Engineering Research and Studies, March 2011;E-ISSN [8]. M.I. Abdul Aleem and P.D. Arumairaj; Geopolymer Concrete - A review; International Journal of Engineering Sciences & Emerging Technologies, Feb 2012;ISSN: [9]. Matthew Kambic, Joshua Hammaker; Geopolymer Concrete: The Future of Green Building Materials; University of Pittsburgh, Swanson School of Engineering; March 2012; Reference No:2099 [10]. Ganpati Naidu, A.S.S.N. Prasad, S. Adiseshu, P.V.V. Satayanarayana; A Study on Strength Properties of Geopolymer Concrete with Addition of G.B.B.S; International Journal of Engineering Research and Development, July 2012; eissn: X [11]. B.J. Mathew, M. Sudhakar, C. Natarajan; Strength, Economic and Sustainability Characteristics of Coal Ash - GGBS Based Geopolymer Concrete; International Journal of Computational Engineering Research, January 2013; ISSN [12]. Prof. More Pratap Kishanrao; Design of Geopolymer Concrete; International Journal of Innovative Research in Science, Engineering and Technology, May 2013; ISSN: [13]. M.C.M. Nasvi, P.G. Ranjith, J. Sanjayan; Effect of different mix compositions on apparent carbon dioxide permeability of geopolymer: Suitability as well cement for sequestration wells; June 2013; ISSN: [14]. S.H. Sanni, R.B. Khadiranaikar; Performance of Alkaline Solutions On Grades of Geopolymer Concrete; International Journal of Research in Engineering and Technology, November 2013;eISSN: P R ADIK,G A GUND,N A SHAH, S P DATTA and Y R LALAI ijesird, Vol. II Issue XII June 2016/751