Alkaline Activation of Ferrous Foundry Sand: A Look at the Effect of Activator Concentration, Liquid-Solid Ratio and Curing Temperature

Abstract

In this study, ferrous foundry slag was used as a precursor for the synthesis of a geopolymer. The effect of NaOH concentration, liquid solid ratio (L/S), and curing temperature on the unconfined compressive strength (UCS) of the synthesized geopolymer was investigated. The optimum concentration was found to be 15 M as it yielded a geopolymer brick with the highest UCS of 8.2 MPa. It was observed that as the concentration of NaOH increases the dissolution of alumina, calcium and silica increases resulting in higher UCS. The SEM results showed zeolite formation in large quantities at 15 M which shows that the geopolymerization reaction was near completion and the calcium, alumina and silicates dissolved in large quantities leading to increased gelling of C-S-H and C-A-H over time filling more pores inside the geopolymer brick. The liquid to the solid ratio that gave the highest UCS of 8.2 MPa was 0.15. The optimum temperature was found to be 80 °C. This increased temperature favoured the dissolution of reactive species and contributed to higher UCS. The results reveal that ferrous foundry sand geopolymers have the potential to be used as a building and construction material.