Durability performance of sustainable structural concrete: Effect of coarse crushed concrete aggregate on rapid chloride migration and accelerated corrosion

The increasing use of crushed concrete aggregates (CCA), formerly referred to as recycled concrete aggregates (RCA), has led to research into the effects of coarse CCA in higher value structural applications. Concerns exist regarding the effect on chloride ion ingress which ultimately can cause deterioration of reinforced concrete. This concern is reflected in existing European and British concrete design standards as limitations prevent their use in environments where chlorides may be present. The rapid chloride migration coefficient and rate of accelerated corrosion of structural CEM I and CEM III/A CCA concretes was measured to determine the effect on chloride ion ingress. Three sources of coarse CCA were evaluated; results show that coarse CCA generally had a detrimental effect on the chloride ion ingress of structural concrete. However, these effects can be mitigated by the inclusion of GGBS to produce structural CEM III/A concretes, thus allowing higher proportions of coarse CCA. It is recommended that the GGBS and coarse CCA content be limited to 50% and 60% respectively as this reduces the risk of a significant detrimental effect on chloride ion ingress. The results also suggest that the limitations in existing European and British standards are conservative and sustainable structural CEM III/A concrete with the inclusion of coarse CCA could be a viable option for future responsibly sourced projects, provided that a reliable and consistent source of CCA can be obtained. This is a positive outcome for the wider implementation of coarse CCA into structural concrete applications.