Mechanical performance and microstructure improvement of soda residue–carbide slag–ground granulated blast furnace slag binder by optimizing its preparation process and curing method

Abstract

To optimize the early mechanical performance of soda residue - carbide slag - ground granulated blast furnace slag (SCG) binder and expand its application scope, the effect of the preparation process and curing method on the performance of SCG binder was investigated. The optimized preparation process and curing method were determined based on the strength evolution trends of specimens under different preparation processes and curing methods, as well as XRD, FTIR, TG-DTG, and SEM characterizations. The results demonstrated that enhanced mechanical performance could be achieved by directly using soda residue and carbide slag slurry to prepare the SCG binder. Compared with specimens prepared by conventional powder + water, specimens' compressive strengths after 3 and 28 days were enhanced by 50.0 and 34.7%, respectively. This can be attributed to the fact that alkali wastes in the slurry accelerated the ground granulated blast furnace slag (GGBS) hydration, promoting the generation of C-S-H gel and Calcium chloroaluminate hydrate (FS) crystals. Curing at 60 ℃ for 12 h was proved to be the optimal high-temperature (HT) curing method: compared to water-cured specimens, it improved the 3-day compressive strength by 66.7%. This improvement can be attributed to the thermal conditions accelerating decomposition and polymerization of GGBS, thus promoting the generation of C-S-H gel and FS crystals and enhancing the structure compactness. The HT curing can also facilitate the generation of Hydrotalcite and Calcite crystals, but its effect on the strength is negligible. Besides, excessive curing temperature (over 60 ℃) and HT curing period (over 12 h) result in late strength degradation by promoting the development of contraction cracks in the C-S-H gel matrix. This study provides a theoretical basis for the wider engineering application of SCG binder.