Roles of particle packing and water coating thickness in carbonation and strength of γ-dicalcium silicate-based low carbon materials

Abstract

In this work, a low carbon material of γ-dicalcium silicate (γ-C2S) was examined, with an emphasis on the properties influenced by its particle packing and water coating thickness (WCT). Differences in morphology and reactivity from that of cement particles render γ-C2S particles have different particle packing behavior and water film surrounding each particle. However, limited research has been conducted on it to deepen the understanding of γ-C2S-based materials. To fill this gap, the wet packing density of γ-C2S particles was measured and the WCT was varied at different water to solid ratios. At each WCT, the carbonated γ-C2S samples were characterized by techniques of X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) consistently. Experimental results revealed little early strength gain when the WCT exceeded a certain value. Moreover, a critical carbonation depth was identified. Below the critical depth, the amounts and characteristics of carbonation products dominated, whilst above the critical depth, the strength gain was influenced by CO2 diffusion rate. An optimal WCT exists for achieving the highest strength and CO2 uptake. This work shall advance the development of low carbon γ-C2S-based materials from the perspective of particle packing.