Mechanical and Durability Studies of Fly Ash and Bottom Ash Based Geopolymer Concrete at Ambient Temperature

Abstract

Concrete is most used material after water on the planet. Ordinary Portland cement (OPC) is used as the binder material for producing the concrete. Due to increase in demand of infrastructure facility, use of concrete is increasing day by day. Production of cement requires not only lot of natural resources but it also produces of lots of gases such as carbon dioxide. One ton cement production requires 2 tons of shale and limestone and releases 1 ton CO2 , 3 kg NO and airborne particulate matter that is harmful to the respiratory tract when inhaled. Hence the Ordinary Portland cement (OPC) is not environmental friendly. One alternative material for the Ordinary Portland Cement (OPC) is inorganic alumina silicate polymer called geopolymer. It uses industrial waste materials like fly ash, bottom ash, and slag as source material. By exploring use of the fly ash based geopolymer concrete two environment related issues are tackled i.e. the high amount of CO2 released into the atmosphere during production of OPC and utilization of fly ash. Experimental work was carried out to develop mix design using fly ash and bottom ash as source material. Parametric study was done to evaluate the effect of variation of different parameters on compressive strength of geopolymer concrete with fly ash and bottom ash as source material. Variation was done in proportion of fly ash and bottom ash, molarity of alkaline solution, ratio of alkaline solution, ratio of cementitious material to alkaline solution, amount of extra water. Ambient curing technique was adopted in place of heat curing technique so that it becomes practically feasible to implement the mix design. Mix design was finalized for optimum content of fly ash and bottom ash for M 25 grade of concrete. Determination of durability of geopolymer concrete with fly ash and bottom ash combination was done by performing various test like sulphate resistance, acid resistance, chloride attack, water absorption, sorptivity, accelerated corrosion test, RCPT, carbonation test and high temperature resistance test. Results were compared with control concrete of M 25 grade to determine change in behaviour. For sulphate, acid and chloride performance of the concrete evaluated based on visual appearance, change in mass and change in compressive strength. Water absorption and sorptivity test were carried out in order to evaluate amount of water absorption in concrete due to voids and due to capillary action. Accelerated corrosion test performed to evaluated corrosion resistance property of geopolymer concrete. Effect of high temperature was evaluated by conducting the test at three different temperature such as 500° C, 700°C and 900°C . Residual compressive, split tensile and flexural strength was evaluated and compared with normal concrete. For reinforced geopolymer concrete specimen, load carrying capacity, load-defection relationship, mode of failure and crack pattern observed. Bottom ash and fly ash combination can be used in equal proportion for M 25 grade of concrete and geopolymer concrete prepared from it possess good durability compared to ordinary concrete. Also behaviour of reinforced concrete specimen was similar to OPC concrete beam specimen. This shows that Sodium based alkaline activators can be used for manufacture of geopolymer concrete with fly ash and bottom ash combination in equal proportion.