Experimental study on CO2 curing for enhancement of recycled aggregate properties

• CO2 curing is used to enhance the properties of recycled concrete aggregates (RCA).
• CO2 curing can densify the mortar adhered on RCA to increase the density of RCA.
• CO2 curing can reduce the water absorption and porosity of RCA.
• Factors influencing the CO2 curing process are identified.

In this paper, the results of an experimental program on studying the use of a carbonation process to enhance the properties of recycled aggregates are presented. Hardened concretes prepared by using different water-to-cement ratios in the laboratory, were crushed to produce recycled aggregates with different particle sizes. Before and after the laboratory carbonation process, the physical properties of the recycled aggregate, including water absorption and density were determined. The extent of CO2 curing of the recycled aggregate was quantified by assessing the carbonation percentage of the aggregates. Carbonation resulted in reduction in water absorption values and increase in density and these showed that the properties of recycled aggregate were improved. The factors influencing the CO2 curing process, including curing time, particle size and moisture contents of the recycled aggregate, were investigated.