Application of Double-Coated Recycled Concrete Aggregates for Hot-Mix Asphalt

Bituminous mixtures made with recycled concrete aggregates (RCAs) exhibited inferior properties than those containing natural aggregates only. This is mainly because the old cement mortar attached to RCA surfaces and other impurities such as bricks and tiles. In this study, new state of the art coating technique was developed to improve the behaviour of RCA-asphalt mixtures. The technique was based on combining two treatments: coating and heating. It was therefore referred to as a double coating technique (DCT). Mixes made with 0%, 20%, 40%, and 60% of double coated recycled concrete aggregates (DCRCAs) were evaluated through Marshall parameters, indirect tensile strength (ITS), tensile strength ratio (TSR), and indirect tensile stiffness modulus (ITSM) tests. The results indicated that the DCT improves strength, and stripping resistance of bituminous mixes. The DCRCA-asphalt mixtures, had a lower wet tensile strength and TSR in comparison with control mix. The DCRCA-mixtures, however, exhibited better tensile strength, higher resistance against moisture, and higher resilient modulus compared to those made with uncoated RCAs. Asphalt mixtures made with DCRCAs also achieved better stiffness than control mix up to 40% granite aggregates substitution. Although the results obtained are satisfactory, other mechanical properties (Fatigue life, rutting and dynamic modulus) of HMA made with DCRCAs require further evaluation.