Influence of Various Soluble Carbonates on the Hydration of Portland Cement studied by X-ray Diffraction

The effect of limestone on the hydration of Portland cement has been studied by many researchers. However, a possible influence of adding more soluble carbonates was not explained. Therefore we executed a qualitative and quantitative research on the influence of slightly soluble (CaCO 3 , MgCO 3 , dolomite), medium soluble (Li 2 CO 3 ) and highly soluble (K 2 CO 3 and KHCO 3 ) carbonates on the hydration. Blending of Portland cement with differently soluble carbonates was found to influence the hydrate assemblage of the hydrated cement. With the help of the Rietveld analysis, the study indicated that the amount of reacted carbonate in cement hydration at a 15% addition of slightly or medium soluble carbonates does not exceed 5% and is not affected by their solubility; at a 15% addition of the highly soluble carbonate K 2 CO 3 the amount of reacted carbonate was around 6%. An increase in temperature (25 to 40 °C) gradually affects the rate of hydration and the quantity of stable phase assemblage.