Clinker-free binder based on kaolinite-rich coal gangue powder, slag, calcium carbide residue and soda desulfurization residue: Rheology, mechanical performance and hydration property

Ordinary cement is often reported to cause high carbon emission, and it is essential to develop an ecological and high performance binder. This study introduced a new clinker-free binder performing excellent mechanical performance. Calcium carbide residue (CCR) and soda desulfurization residue (SDSR) were invited as activators, and ground granulated blast-furnace slag (GBFS) with calcined coal gangue powder (CCGP) were treated as precursors. The rheological, mechanical and hydration properties of pastes were investigated respectively. The results showed that the rheological properties of pastes fitted well with Herschel-Bulkley model and exhibited shear thinning behavior. The incorporation of CCGP increases the yield stress and inhibits shear thinning phenomenon. The compressive strengths indicated that the optimal CCGP content was 20 wt%, and its incorporation restricted hydration reaction rate and autogenous shrinkage, resulting in a denser microstructure. Metakaolin within CCGP produced typical hydration products of ettringite, C-A-S-H and N-A-S-H, and prompted hydration reaction from alkali activated materials to geopolymer cement. This study reported a clinker-free binder utilizing solid wastes and confirmed its feasibility in construction applications.