Effect of Carbonation Curing on the Performance of Concrete Containing Recycled Aggregates from Returned Concrete

The stringent quality control measures on the properties of concrete result in the production of a large quantity of returned concrete in many countries. Waste management strategies include extracting the aggregates from this returned concrete to reduce the consumption of natural aggregates. This study aims to extract and characterize the recycled coarse aggregates (RCAs) obtained from returned concrete by using superabsorbent polymer (SAP) additives (RCA-SAP), and by washing (RCAW), and to compare the properties with local specification for recycled aggregates. Furthermore, the comparative performance of the concrete containing those two types of differently treated recycled aggregates as partial replacements for natural aggregates (NCAs) under accelerated carbonation and water curing was analyzed through strength, water absorption and gas adsorption tests. Quality testing revealed that RCA-W outperforms RCA-SAP in terms of water absorption and abrasion resistance. RCA-W showed a water absorption of 1%, compared to a value of 4.5% for RCASAP. Also, a Los Angeles abrasion value of lower than 30% was observed for RCA-W, indicating better abrasion resistance compared to RCA-SAP. The concrete containing polymer-modified recycled aggregates at a 30% replacement showed a maximum strength of 60.44 MPa under carbonation curing and 51.93 MPa under water curing, indicating 16.4% higher strength under carbonation curing. In summary, it was confirmed that carbonation curing enhances the concrete performance with polymermodified recycled aggregates.