Technical noteDevelopment of rubberized geopolymer concrete: Strength and durability studies
Introduction
Global development of infrastructures and constructions to cope with the mushrooming world population is driving to a gigantic exigency of concrete. Concrete has been revolutionized since Romans and its use is highest as a construction material on the earth [1], [2], [3]. It requires essentially Ordinary Portland Cement (OPC) as a binder and hence, the demand for OPC is also pushy. However, the production process for OPC is quite in the wrong as it not only takes place at elevated temperature consuming high energy in form of burning up of natural restricted mineral coal resources but also emits CO2 into atmosphere bringing bad news of heating the earth and polluting of air. CO2 is a primary Green House Gas (GHG) responsible for world concerning gigantic dilemma of global warming [4], [5], [6], [7], [8]. The aggregates sought-after for manufacturing concrete and mortar and raw materials for OPC are also degrading day by day due to haphazard mining and no stringent rules for it in some countries. These altogether forms the core reasons to twist the arm of researchers, scientists and engineers to search for alternative construction materials that should be essentially sustainable, durable, user and eco-friendly and more significantly economically affordable.
A solution to all these predicaments is hopefully lies with innovative Geopolymeric construction materials. Geopolymers are an inorganic materials produced at low temperature in alkali medium through the process of Geopolymerization – a synthesis which is as analogous as geo-synthesis of natural rocks, whereby Aluminium and Silicates rich precursors react in an exothermic way with alkali activators to give rise to Geopolymers [4], [5], [6], [7], [8], [9]. They not only exhibit excellent thermal, fire, and freeze thaw resistance but also consume six times less energy and nine times less CO2 emissions. That means, no high energy and high temperature reactions are essential any more through providing 21st century modern construction materials of Geopolymeric origin. Not only that, they devour diverse profuse waste, otherwise filling landfills creating health hazards, making it more economical [10], [11], [12]. Therefore, this present era researchers are inclined towards this user and eco-benign construction technology. Beforehand, crumb rubber was utilized as partial replacement of fine aggregate in geopolymer composites [13], [14], [15], [16]. For instance; Bashar et al. [13], have produced rubberized geopolymer interlocking bricks by employing crumb rubber as fine aggregate. Moreover, Wongsa et al. [14] have reported the mechanical and thermal properties of lightweight geopolymer mortar integrating crumb rubber as fine aggregates. Yahya et al. [15] have explored the seawater resistance of fly ash based geopolymer concrete incorporating crumb rubber as coarse aggregates. Not merely that, Park et al. [16] have also investigated the compressive strength of rubberized fly ash-based geopolymer concrete using crumb rubber as partial substitute of fine aggregate.
A variety of wastes having diverse origin will get a systematic solution for their disposal management through their incorporation with Geopolymer concrete manufacturing which would otherwise contaminating air, soils, surface and sub surface waters in landfills. As we are all aware that the tyres of vehicles and carts are thrown away by automobile and transporting agencies in a titanic quantity in either open spaces filling fertile land as complex wastes responsible for different pollutions and root cause for diseases. An estimated 1000 million tyres reach the end of their useful lives every year and 5000 millions more are expected to be discarded in a regular basis by the year 2030. According to the EUROSTAT report, 1,246,447 tonnes End of life vehicles waste was generated in UK in 2016. Every year, End of life vehicles generate between 8 and 9 million tonnes of valuable waste in the Community. [6], [17], [18]. Roughly, 0.6 million tonnes of scrapped tyres are reported to have been in landfills. Their burning up also creates toxic smell and emissions of lethal gases with restrictions of law in some of the countries.
What’s more, their complex structure is a challenge to their bio-degradation. Consequently, their systematic consumption for good cause is only the best way for this colossal waste management. Analogously, piles of enormous Fly ash are also plentifully accessible as industrial by-products from thermal power stations. It is cementitious pozzolonic material which is useful to develop diverse Geopolymer mortars and concretes. It is found o fill fertile spaces causing great trouble to health of mankind and environments too. Global coal ash production totals more than 390 million tons per year. Out of which, merely 15% is currently utilized. Therefore, its consumption in a systematic way will lend a hand to its management.
The scope of present manuscript is to develop rubberized geopolymer concrete and to comply the performance evaluation of strength studies such as Compressive Strength, Flexural Strength, Split Tensile Strength, Modulus of elasticity, Pull off strength and durability parameter like abrasion resistance of fly ash based rubberized geopolymer concrete and compared the results with OPC rubberized concrete.
Section snippets
Materials
Class-F Fly ash complying with IS 3812 [19] was used as a precursor. The specific surface area 428 m2/g was found. Fig. 1, Fig. 2 and Table 1 shows energy dispersive spectrometer (EDS), The X-ray diffraction patterns (XRD) and chemical composition of fly ash [6], respectively. The texture of fly ash demonstrated in Fig. 3 [6].
River sand was used as fine aggregate to prepare fly ash based rubberized geopolymer concrete. The fineness modulus, specific gravity and water absorption were of 2.56,
Manufacturing process for geopolymer concrete
The key divergence among mixing geopolymer concrete and OPC concrete is of binder material. In the first one, fly ash that is rich in silicon and aluminium oxides reacts with the alkaline solution to produce geopolymeric bonds between the aggregates and other unreacted materials. In the mix design of geopolymer concrete, the total aggregates constituted 75% by mass of the concrete, which is similar to OPC concrete, i.e. 75–80%. Fine aggregates cover 35% of the total aggregate content. The
OPC concrete mix design
The proportions for the OPC concrete mix were calculated based on IS 10262-2009 [21]. The volume of aggregate used in the OPC concrete was in the range 75–80% by mass. The fine aggregate was employed as 35% of the total aggregate. The mixture proportion of OPC concrete is listed in Table 2. Waste rubber tyre fibres were used in concrete as a partial replacement for the fine aggregate. The mixture proportions of OPC concrete are analogous to those of the geopolymer concrete mixture, except for
Strength properties
After heat curing of the geopolymer specimen, strength properties were appraised according to Indian standards. Comprehensive details of the testing program are described below.
Compressive strength test
The compressive strength of geopolymer concrete measured at 3, 7, 28, 90, and 365 days is shown in Fig. 14. It can be seen that, as the percentage of waste rubber tyre increases from 0 to 30%, the compressive strength decreases at all ages. Decline in compressive strength is ascribed to lesser stiffness of the alternative material as compared to the adjacent fine aggregate. In fact, as the rubber fiber contents increased, the voids are generated due to lesser bonding between rubber fiber
Conclusion
From the results reported in this Research, the following conclusions can be drawn:
- 1.
As the percentage of waste rubber fibres increases, the compressive strength decreases at all ages. Geopolymer concrete, gain 95% compressive strength only in 7 days. The compressive strength of OPC concrete is less than that of geopolymer concrete.
- 2.
The geopolymer concrete exhibits higher tensile strength than OPC concrete because of the good bonding between the geopolymer paste and aggregate.
- 3.
The tension
Conflict of interest
None.
Acknowledgments
The authors gratefully acknowledge the financial support for this research by the Department of Science and Technology, New Delhi, under the Women Scientist scheme (sanction number SR/WOS-A/ET-1016/ 2015) and Material Research Centre (MRC), Malaviya National Institute of Technology, Jaipur for their support in conducting X-ray diffraction, FTIR, TGA/DTA and SEM and XRF analyses respectively.
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