High temperatures effect on mechanical and physical performance of normal and high strength recycled aggregate concrete

In recent years several studies analysed the influence of recycled aggregates obtained from concrete debris (Recycled Concrete Aggregates, RCAs) on the durability performance of structural concrete produced with them (Recycled Aggregate Concretes, RACs) and, within this, also the influence of high temperatures has been investigated. In most cases, the concrete strength has not been considered as a key control parameter for the comparison between RACs and ordinary concrete performance. In this context, starting from a fundamental characterization of the raw materials under high temperatures, this paper presents a comprehensive experimental study on normal- and high-strength RACs mixtures designed with the Compressible Packing Model, with the aim of investigating their residual mechanical and physical performance when subjected to high temperatures (up to 650 °C). This approach allows a generalized analysis by considering the overall amount of attached mortar (AM) that represents the key parameter characterizing RCAs. In fact, since one of the main issues related to the possible use of RCAs in concrete is their significant unknown heterogeneity depending on their original source, the identification of a fundamental parameter such as the AM, allows to extend the conclusion obtained herein for RAC mixtures produced with RCAs derived from different origins.