Influence of incorporating fine green foundry sand waste in the production of geopolymers: study of physical and mechanical properties

Abstract

The aim of this article was to evaluate the physical and mechanical properties of a geopolymeric material developed by replacing metakaolin, a conventional precursor, with fine green foundry sand waste (FGFSW). Substitution ratios of 0% (reference specimen), 5%, 10%, 15% and 20% were used, as well as molar ratios of SiO2/Al2O3 equal to 3.0 and 3.5. The specimens were cured at 7, 14 and 28 days and then tested for compressive strength, water absorption, void ratio, dry density and saturated density. In addition, the specimens were subjected to macrographic tests to assess the geopolymer material. The results showed a reduction in compressive strength as substitution increased. There was also a decrease in density as the substitution increased, as well as an increase in porosity and water absorption in the geopolymer matrix. These effects were attributed to the presence of FGFSW grains which did not take part in the geopolymerization reaction, having a low density and contributing to the reduction in mechanical strength. Finally, incorporating the waste into the production of geopolymers appears to be a possible alternative for disposing of green foundry sand waste.