Using calcium carbide residue to prepare ecological alkali activated slag composites: Effect of anion type

Abstract

Activator is a critical component of alkali activated materials. In the present work, a by-product calcium carbide residue is used to prepare mixed alkali activators combined with sodium carbonate and sodium sulfate, and the properties of alkali activated slag (AAS) pastes versus different activators have been analyzed. The results of the investigation show that the mixed alkali activators with two sodium salts represent different characteristics but better performance compared to single sodium hydroxide. The addition of mixed activators can effectively relieve the rapid hardening and concentrated exotherm of hydration. Meanwhile, mixed activators substituting sodium hydroxide properly enhance the mechanical properties of AAS paste, and change the type and content of hydration products slightly. Further, the SEM testing result indicates that the early shrinkage and calcium-losing are overcome by using mixed alkali activators. These testing results prove the economy, environment, and practicability of mixed alkali activator developed by calcium carbide residue.