Comparison on accelerated carbonation of β-C2S, Ca(OH)2, and C4AF: Reaction degree, multi-properties, and products

Abstract

In-depth understanding regarding the carbonation properties of pure minerals including β-dicalcium silicate (β-C2S), calcium hydroxide (CH), and tetracalcium aluminoferrite (C4AF) was conducted to explore the types, microstructure, crystallinity of products produced during carbonation, thereby developing a tentative microscopic mechanism of the contribution of carbonation to macroscopic properties. An investigation of changes in pH value and Ca leaching of the pure minerals was conducted to explore the effect of dissolution properties to the carbonation. Results showed that the descending order of the ultimate carbonation degrees of minerals was: (i) CH, (ii) β-C2S, (iii) C4AF. The carbonation degrees and rates were not only controlled by the dissolution properties of the minerals, but also the distribution of the produced CaCO3. The order of the contribution of minerals induced by carbonation to the macroscopic mechanical strength was, in descending order: (i) β-C2S, (ii) CH, (iii) C4AF. This difference was the combined effects of the microstructure, crystallinity, and particle size of calcite. Effects of the compact stack and the strong mechanical bond between the calcite particles were observed in carbonated β-C2S samples; In contrast, pronounced defects on the calcite particles were observed in carbonated C4AF samples. Carbonation is an effective way to reduce the density of which mainly contained phases of β-C2S and C4AF, and to store greenhouse gas CO2 permanently. These findings are meaningful for the further in-depth researches of the carbonation mechanism of materials which primarily contain β-C2S, CH and C4AF phases.