High-pressure carbonation of mortar as a model for recycled concrete aggregates

Abstract

Accelerated carbonation is recognized as a possible way to improve the quality of recycled concrete aggregates (RCA) and thus increase the possibilities of their use for concrete manufacturing. This work is a contribution to exploring high-pressure carbonation as a possible technology for carbonation of cement-based RCA. Using mortar powder and cylinders as a model for RCA, the work established that mortar with sufficient water content can be nearly fully carbonated at 138 kg of CO2 per tonne of mortar in less than 30 min with high pressure CO2. The presence of water inside the mortar’s porous structure appeared to be a factor of paramount importance for carbonation of mortar, whereas using water-saturated CO2 was of no benefit. Increasing CO2 pressure and temperature both improved carbonation kinetics of mortar within the range of pressure and temperature conditions tested.