Alkali-aggregate reaction in recycled aggregate concrete

Using recycled concrete aggregate (RCA) to substitute original aggregate (OA) is of significance for sustainable development of construction materials. However, uncertainties remain with respect to the longterm durability of concrete containing RCA. This review article focuses on alkali-aggregate reaction (AAR) of RCA concrete and provides a comprehensive overview of the progress of this subject. The review includes comparison of AAR between RCA and OA concretes; the factors influencing the AAR in RCA concrete; the mitigation measures and the applicability of different test methods for assessing the alkali reactivity of RCA. The reactivity of OA and the remaining reactive component available for secondary AAR in RCA play the essential role in influencing the AAR in concretes containing RCA. In contrast to OA, it is more complicated to assess the AAR potential of RCA due to the variations of the residual mortar (RM) content. (C) 2020 Elsevier Ltd. All rights reserved.