Corrosion risk assessment of structural concrete with coarse crushed concrete aggregate

Abstract

Crushed concrete aggregates (CCA) are an increasingly popular replacement for natural aggregates (NA) in structural concrete due to industry demands for more recycled, low carbon footprint and responsibly sourced materials. There is uncertainty regarding chloride-ion ingress, which can ultimately cause deterioration of reinforced concrete. This is reflected in European and British concrete design standards, which currently exclude CCA in chloride environments. Structural concretes with up to 60% coarse CCA (and CEM I, CEM II/B-V and CEM III/A binders) were exposed to aggressive chloride environments and monitored with electrochemical techniques and subsequent destructive testing to determine their risk of corrosion initiation. The results showed that CEM II/B-V and CEM III/A concretes with up to 60% coarse CCA outperformed the control CEM I concrete with 100% NA, and had a lower risk of corrosion initiation. It is recommended that further monitoring is required over longer periods to determine the corrosion-initiation risk. Supplementary cementitious materials had a beneficial effect on the chloride-ion ingress resistance, significantly increased the predicted time to corrosion initiation beyond the 50-year design life and largely outweighed any observed detrimental effects from an increased coarse CCA content, suggesting that limitations imposed by existing design standards are conservative.