Study on heat resistance of carbonated γ-C2S binder: Strength, phase and microstructure evolution

Abstract

The dissimilarity of composition and microstructure in hydration and carbonation binders induces different performances. In this study, the heat resistance of carbonated γ-C2S binder subjected to elevated temperature were investigated by evaluating the residual mechanical strength, composition and microstructure evolution. The results show that the carbonated γ-C2S binder can endure the heating of 600 ℃. Moreover, heat treatment at 500 ℃ improves 60 % of the compressive strength of the carbonated γ-C2S binder, while heating of 700 ℃ leaves only 22 % of the strength. XRD pattern analysis indicates that the enhanced crystallinity of calcite from 400 to 500 ℃, accompanied by the transformation from aragonite to calcite, is the key factor that strengthened the matrix. The cliff-like drop of compressive strength at 700 ℃ is caused by the decomposition of calcium carbonate and silica gel, which disconnects the grains and generates pores and cracks among the particles.