Strength and Durability Properties of Low Calcium Fly Ash Based Geopolymer Concrete

Abstract

With the fast growing infrastructure development, the demand of cement is bound to increase. But in producing 1 tonne of cement, around 1 tonne of carbon dioxide is released. For the changing environment, green house gases such as carbon dioxide, carbon monoxide, etc have been considered as responsible which also enhance the most hazardous environmental problem of global warming. This clearly reflects the inability of cement concrete to fit in the contemporary picture of sustainable development. On the other hand, various industrial by-products such as fly ash, metakaolin, slags, etc have prompted their use as supplementary cementitious material due to their cement like physical and chemical properties. Geopolymer technology utilizes these industrial by-products having high silica and alumina in the production of binders by polymerization reaction. The reaction is activated by hydroxides and silicates of alkalis such as sodium or potassium. The present research work involves the development of low-calcium fly ash based geopolymer concrete. Control geopolymer concrete with 3-day compressive strength of 41.3MPa was developed with fly ash content of 310 kg/m3, alkali solution-to-fly ash ratio of 0.55, sodium silicate-to-sodium hydroxide ratio of 2.5, total aggregate content of 70%, molarity of sodium hydroxide as 10M,fine aggregates-to-total aggregates ratio of 0.35and temperature curingat 80 and#778;C for 24 hours. Further, additional geopolymer concretes were made by partially replacing fly ash with Ordinary Portland cement (OPC) (5-30%). Workability properties such as slump and compaction factor, strength properties such as compressive strength and split tensile strength, and durability properties such as water absorption, porosity sorptivity, chloride permeability and resistance to sulphuric acid solution were performed up to the age of 365 days. For reference, conventional cement concrete of similar 28-day compressive strength was also developed and properties were evaluated.