Influence of the pre-saturation of recycled coarse concrete aggregates on concrete properties

Abstract

The properties of structural concrete which incorporates recycled coarse concrete aggregates (RCCA) may be affected by the RCCA's properties, especially in terms of water absorption, if no technological control methods are adopted in its production. Based on the knowledge of RCCA's water absorption behaviour, this research is aimed at determining the influence of the pre-saturation of the RCCA method on concrete's fresh and hardened properties, compared with a conventional concrete and a recycled aggregates concrete produced using the mixing water compensation method. Both methods can be easily adopted at concrete plants or construction sites. For the establishment of the pre-saturation method procedure, RCCA absorption was thoroughly characterised. A reference concrete and three mixes with replacement ratios of 20%, 50% and 100% of natural coarse aggregates by RCCA were produced, for each method. Tests were performed to determine slump, density, compressive strength, elasticity modulus, shrinkage, water absorption by immersion and capillary water absorption; the surfaces of the mixes were also observed with a magnifying glass. Results showed that mixes produced with the pre-saturation method exhibited slightly worse fresh and hardened properties, and therefore it is concluded that both the pre-saturation method and the mixing water compensation method can be adopted.