Effects of limestone powder on CaCO3 precipitation in CO2 cured cement pastes

The concept of using limestone powder as supplementary materials to accelerate cement hydration has been explored widely. There have also been interests in using CO2 curing to enhance the early strength of concretes. This study investigated the effects of incorporating limestone powder on CO2 curing of cement-based materials. The results showed that using limestone powder to partially replace cement could significantly increase the CO2 curing degree of the cement pastes. QXRD analysis showed that calcite was the major reaction product, accompanied by amorphous calcium carbonate. The mass ratio of poorly crystallized calcium carbonate to highly crystallized calcium carbonate (DC/HC ratio) formed was affected by both the applied CO2 pressure and the use of limestone powder. At low pressure, incorporating limestone powder led to an increase in the DC/HC ratio. However, a reversed trend was observed in the case of high CO2 pressure. (C) 2016 Elsevier Ltd. All rights reserved.