Design of structural concrete mixtures containing fine recycled concrete aggregate using packing model

Abstract

Studies are being carried out around the world aiming at the reuse of Construction and Demolition Waste (CDW). Special attention has been given by the researchers to the coarse fraction of Recycled Concrete Aggregates (RCA). However, when the concrete wastes are processed to obtain the coarse particles, a large amount of Fine Recycled Concrete Aggregate (FRCA) is generated depending on the origin of the residue. As the studies on the use of FRCAs in structural concrete are scarce, the present paper aims to analyses the extension of the Compressible Particle Packing Model (CPM) for the mixture proportioning of normal- and high-strength recycled concrete (i.e., C30 and C60) containing different levels (i.e., 0%, 25% and 50%) of recycled sand obtained from different origins of concrete waste. The concretes produced with FRCA showed mechanical properties similar to the reference mixtures produced with natural aggregates. Total and capillary absorption were higher for concretes containing demolition residues, due to higher water absorption. Drying shrinkage and chloride ions penetration were higher for recycled concrete, and the higher the FRCA content in the mixtures, the more expressive is the increase. The CPM showed to be quite adequate for the mix design of concrete containing different FRCAs, as the method did not affect mechanical behaviour and the durability performance.