Hydration and carbonation of monoclinic C2S and C3S studied by Raman spectroscopy

We present a micro-Raman study on the hydration and carbonation of the main silicate phases of Portland cement, i.e. monoclinic dicalcium silicate (C2S) and monoclinic tricalcium silicate (C3S). We investigate the reaction products and the loss of crystallinity induced by hydration on these two compounds. In the CO2-contaminated pastes we find that calcite, aragonite, and vaterite are inhomogeneously formed. We study sample cross sections to evaluate the maximum depth at which CaCO3 is formed. We find that carbonation is limited to the first 500-1000 mu m from the surface in the C3S pastes, while in C2S pastes CaCO3 is formed well beyond this depth. Our results show the great potential of Raman spectroscopy in the study of the chemistry of cements. Copyright (c) 2006 John Wiley & Sons, Ltd.