Durability performance of structural concrete made with coarse recycled concrete aggregates

There is often a poor perception of the durability of concrete made with recycled concrete aggregates (RCA), as well as concerns regarding performance variability and contamination of the source material. Additional research regarding the addition of RCA in structural concrete is therefore required to more clearly determine the limits of its suitability. The influence of RCA on the mechanical properties of concrete has been well investigated; the effect on durability however, is less well understood. Chloride ions can be particularly detrimental to the durability of reinforced concrete and BS 8500 currently allows RCA in strength classes up to C40/50 for structures unlikely to be exposed to de-icing salts and marine environments during their design life. This research investigated the effect of coarse RCA in combination with supplementary cementitious materials on the resistance to chloride ingress of concrete in terms of surface resistivity, sorptivity and rapid chloride migration testing. Compressive cube testing was conducted to determine compliance with characteristic and target mean strengths. The results indicate that a higher replacement of natural aggregates with RCA causes a reduction in the resistance to water and chloride ingress, possibly due to the higher water absorption characteristics of the RCA. PFA and GGBS reduced the rate of water and chloride ingress compared to Portland cement concretes for all coarse RCA increments tested.