Reaction kinetics, microstructure and phase evolution of alkali-activated Si-Mn slag during early age

Alkali-activated material with Si-Mn slag (SiMnS) as precursor is regarded as an efficient way of resource uti-lization in large-scale and green mode. This study aims to investigate the reaction kinetics, microstructure, and phase evolution of alkali-activated SiMnS during the early age. The reaction kinetics of SiMnS activated by water glass with different modulus was studied by isothermal calorimetry, the phase and the microstructure evolution of reaction products from alkali-activated SiMnS at typical alkali activation reaction (AAR) times (15 min, 30 min, 1 h, 3 h, 12 h, and 24 h) were studied by XRD, FTIR, SEM, BET, and thermogravimetric experiments. Reaction kinetics analysis showed that alkali-activated SiMnS exhibited two main exothermic processes attrib-uting the generation of Si-rich gel (mainly C-S-H) and Al-rich gel (mainly C(N)-A-S-H) respectively. The alkalinity and existence form of polymeric silicate of alkaline activator (AA), which depend on the modulus of AA, determined the intensity of AAR and the characteristics of AAR process respectively. Characterization results of samples indicated that alkali-activated SiMnS could be divided into three steps: formation of Si-rich gel, for-mation of Al-rich gel, increase of gel polymerization degree, and maturation, respectively. SiMnS can be an alternative raw material in the alkali-activated application.

Automated summary

This study investigates the reaction kinetics, microstructure, and phase evolution of alkali-activated Si-Mn slag (SiMnS) as a precursor. The results show that alkali-activated SiMnS exhibits two main exothermic processes, the generation of Si-rich gel and Al-rich gel. The alkalinity and the existence form of the alkaline activator determine the intensity and characteristics of the alkali activation reaction. SiMnS can be used as an alternative raw material in alkali-activated applications.