Effect of the source concrete with ASR degradation on the mechanical and physical properties of coarse recycled aggregate

Knowing the aggregates' properties is fundamental for the correct design and performance prediction of concrete. The incorporation of coarse recycled aggregate (CRA) in concrete requires a deep understanding of CRA's capacity and limitations. CRA properties are mainly conditioned by the type of natural aggregates (NA), the interstitial transition zone (ITZ), and the adhered mortar's quality. All these conditions are restricted by the chemical, physical, and mechanical properties of the source concrete (SC). The potential alkali reactivity of CRA raises the alkali-silica reaction (ASR) issue when CRA incorporation in concrete is an option. The heterogeneity of CRA affects the reactive silica and alkali content present in NA and in the adhered mortar, respectively, depending on the characteristics of the SC. This makes it difficult to analyse the influence of CRA's heterogeneity when ASR-effected SC is used. This work intends to investigate modifications of CRA properties due to ASR level in the SC. For this purpose, several tests including ASR evaluation, particle size distribution, density and bulk density, water absorption, shape index, flatness index and fragmentation resistance were performed on NA (fine and coarse) and CRA under natural and accelerated aging conditions. The results shown that the use of ASR-effected CRA does not change its mechanical and physical properties. In fact, these properties are more dependent on the corresponding characteristics of NA, ITZ, and the adhered mortar than on the ASR level in the SC.