Accelerated carbonation of recycled concrete aggregate in semi-wet environments: A promising technique for CO 2 utilization

YN Gao and Y Jiang and Y Tao and PL Shen and CS Poon, CEMENT AND CONCRETE RESEARCH, 180, 107486 (2024).

DOI: 10.1016/j.cemconres.2024.107486

The practical implementation of accelerated carbonation for recycled waste concrete is impeded by sluggish carbonation efficiency. In contrast to previous carbonation enhancement schemes using high-pressure gas and/or complex pre -/post -processing, this study introduces a novel semi -wet carbonation method that achieves highefficiency carbonation of recycled concrete aggregates (RCA) in a practically simple way. A noteworthy carbonation degree of 10.6 % was achieved within 30 min at room temperature and ambient pressure, which enhanced the RCA by reducing the water absorption rate and porosity by 3.6 % and 20 % respectively. The formed CaCO 3 is primarily in calcite form with poorer crystallinity and smaller grain size and the formed silica gel features a lower polymerization degree compared with those formed in wet carbonation. It is due to that the carbonation reactions for the semi -wet scenario happen at the spatially confined water film of the solid -liquid interface. Moreover, the addition of sodium bicarbonate significantly accelerated the semi -wet carbonation, which is due to the weak alkaline environment lowering the CO 2 speciation free energy as revealed by reactive molecular dynamics simulations. The proposed semi -wet carbonation method provides a promising way of pushing industrial CO 2 capture and utilization.

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