Wet-carbonation-based Mineral Extraction and CO₂ Sequestration Using Concrete Waste Fines at a Low Temperature

Abstract

This study investigates the wet carbonation of concrete fines with CO 2 and natural air gas bubbling in a carbonation system at low temperatures. After the air-and CO 2 -wet carbonations, the properties of a solution and hydrated cement paste powder are determined. In the air and CO 2 -wet carbonations, more Ca is extracted into the solution at a low temperature of 5°C. This high Ca concentration in the solution through air-wet carbonation primarily originates from the portlandite and unhydrated phases of the cement paste. Even in solutions with high pH values, the rehydration process and C-S-H decomposition occur simultaneously in air-wet carbonation. Moreover, CO 2 -wet carbonation indicates that the decalcification of C-S-H occurs rapidly, even in the presence of portlandite. Air-wet carbonation presents a potential method for the direct air capture of CO 2 using concrete waste fines in a short period.