Comparative study of geopolymer and alkali activated slag concrete comprising waste foundry sand

Abstract

Abstract Concrete industry and current construction practices are highly unsustainable from the standpoint of energy consumption and their high dependence on natural resources. Using alternative binders to conventional cement such as geopolymers and alkali activated slags (AAS) can be one alternative. Besides, reusing industrial by-product and waste materials in construction industry can also be emphasized. These measures can substantially lower the carbon emissions and embodied energy of concrete along with solving the problem of industrial waste disposal. The current study reports the influence of inclusion of waste foundry sand (WFS), a by-product from foundry industries, on strength, permeability and microstructure of low calcium fly ash geopolymer concrete (GPC) and ground granulated blast furnace slag (GGBS) based alkali activated slag (AAS) concrete, both cured in ambient conditions. The mix proportions for both the concretes were kept same. The natural sand was replaced by WFS in the range of 0% to 100% at an interval of 20%. Tests on hardened concretes, to study, compressive strength, split tensile strength, capillary suction, SEM and EDS analysis, were conducted to assess the strength, permeability and microstructure of both types of concretes. Addition of WFS lowered the workability of GPC and AAS concretes and the effect was abrupt beyond 40% WFS replacement level. Strength and sorptivity of both concretes improved upto 60% WFS replacement in GPC, whereas, upto 20% replacement in AAS concrete mixes, besides more than 45% of strength of reference concretes (0% WFS) was achievable at 100% replacement by WFS.