Reaction of Calcium Silicates with Carbon Dioxide and Water

摘要

The reaction of five calcium silicates with CO2 water were investigated. The calcium silicates differed in Ca/Si ratio or polymorphic type. Reaction kinetics were dependent on the Ca/Si ratio of the initial calcium silicates. Activation energy for the carbonation reaction ranged from 9.8 kcal/mole for Ca3SiO5 to 22.9 kcal/mole for CaSiO3. The reaction products were calcium carbonate (CaCO3) and a calcium silicate hydrate of variable stoichiometry. The Ca and H2O content of the calcium silicate hydrate product decreases with degree of reaction. This results in the final stable reaction products consisting of calcium carbonate and a highly polymerized hydrous silica gel which is insoluble in HCl. Calcite forms during the carbonation of Ca3SiO5, beta-Ca2SiO4, and gamma-Ca2SiO4 if free water is present. Aragonite forms in the absence of free H2O and in the carbonation of CaSiO3. The carbonation reaction decreases rapidly at CO2 pressures <0.12. At pressures from 0.12 to 54 atm the carbonation reaction increases, but at a slow rate. Temperature and relative humidity have significant influences on the rate of carbonation. (Author)