Dosagem científica de concretos estruturais contendo agregado miúdo de resíduo de concreto

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 residues are processed to obtain the coarse aggregates, a large amount of fine 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 work aims the mix design of concrete of resistance classes C30 and C60 containing different levels (0, 25% and 50%) of recycled sand obtained from concretes of different origins. The sources of concrete residues for the production of RCAs were: (i) laboratory-produced concrete residue (LAB) and (ii) concrete residue obtained from demolition (D). For the mix design of the concretes the Compressible Particle Packing Model (CPM) was used and adapted to take into account the different water absorption capacities of the FRCAs used. As the FRCAs have different amount of attached paste in their composition, the paste volume was determined by immersion of the aggregates in acid and correlated that volume with the density and water absorption of the particles. The concretes produced with FRCA showed mechanical properties practically equal to the reference concretes. Total and capillary absorption were higher for concretes containing Sand D (higher water absorption). Drying shrinkage and chloride ions penetration were higher for recycled concrete, and the higher the AMRC content in the mixtures (mainly from Sand D), the more expressive the increase. The CPM showed to be quite adequate for the mix design of concrete containing different FRCAs.