Mechanical properties and hydration of fly ash-based geopolymers modified by copper slag

Abstract

Copper slag (CS) is mostly used as concrete aggregate due to its low activity, which limits its application. Although CS can exhibit high activity in geopolymer systems, the mechanical properties of high-volume CS geopolymers are still poor, which limits the utilization of CS and the application of geopolymers. In this paper, CS and fly ash (dry grinding fly ash (DFA) and wet grinding fly ash (WFA)) were used to prepare geopolymers with high-volume CS, and the effects of CS on the mechanical properties, microstructure and hydration of fly ash-based geopolymers were investigated. The results showed that the addition of CS could effectively improve the compressive strength of fly ash-based geopolymers. Compared with geopolymer samples without CS, 40 % CS can increase the 7d and 28d compressive strength of dry grinding fly ash-based geopolymers by 37.8 % and 33.6 %, respectively; 50 % CS can increase the 7d and 28d compressive strength of wet grinding fly ash-based geopolymers by 59.2 % and 49.2 %, respectively. The addition of CS can promote the formation of N(C)-A-S-H and Fe-rich gels, and then improve the mechanical properties and microstructure of fly ash-based geopolymers.