Sustainable development and preservation of environment for future generation are the need of the hour. It is very much essential to have an alternative to cement due to its disadvantage of large emission of carbon dioxide into atmosphere and highly energy-intensive process. Geopolymer concrete is an alternative to conventional concrete. This paper presents a study carried out on the combination of industrial waste fly ash and slag as source materials and the factors affecting the compressive strength of oven cured specimen. The ratio of alkaline liquid to source material was kept at 0.4, the rest period at 1 day and temperature at 90 °C. The density of geopolymer concrete was kept approximately equal to 2400 kg/m3 equivalent to conventional Ordinary Portland Cement (OPC) concrete. It was found that compressive strength of geopolymer concrete increased with increase in curing duration. Increase in strength was also observed with increase in molarity and increase in alkaline solution ratio. Also, if dosage of superplasticizer increased, workability also increased, and it led to increase in compressive strength.

It is a well-known fact that usage of concrete is second only to water. Concrete is the most widely used construction material which is made of cement, sand, crushed stone and water. Of all these materials, cement is the chief ingredient, the demand for which is increasing by leaps and bounds due to the tremendous growth in infrastructure and rapid industrialization. For sustainable development, cement industry today faces two important challenges: reduction of particle matter and gas emissions. It is a known fact that one ton of cement production emits one ton of carbon dioxide, besides using the lean natural resources present. Globally, it is assumed that by 2025, the cement industry will be emitting CO2 at the rate of 3.5 billion tons/year, more or less equal to the total emission made by ‘transport and energy sector’ of today’s Europe (Caijun et al., 2011). Malhotra (2002) discussed how cement production, being an excessively energy-intensive process, raises serious environmental concerns. Also, durability of Ordinary Portland Cement (OPC) concrete structures is a very serious concern. With the rise in power consumption and industrial growth, waste disposal from these industries is also an issue to be looked into. Today, the effective use of fly ash is a big challenge. To address the above issues, there is a serious need to find a viable alternative to cement and one of the promising research areas has been alkali-activated concrete.

Geopolymer concrete or alkali-activated concrete uses waste products from different industries like fly ash, granulated blast furnace slag, etc. as a binder and relies on alumina silicate rather than calcium silicate hydrate for structural integrity. Davidovits (1994) proposed that an alkaline liquid which can react with the Silicon (Si) and Aluminum (Al) in a source material of geological origin or in any by by-product material can be used to produce these binders. Since chemical reaction is a process of polymerization, he termed it as ‘Geopolymer’. The alkaline liquids are from soluble alkali metals which are sodium or potassium-based. Sodium hydroxide (NaOH) or potassium hydroxide (KOH) and sodium silicate or potassium silicate are most widely used alkaline liquids. Hardjito et al. (2004) studied fly ash-based geopolymer concrete and compared it to OPC, and indicated that its resistance to acid attack and permeability characteristic is better compared to OPC.

Structural Engineering Journal, Fly ash, GGBFS, Alkaline liquid, Compressive strength