The effect of fine crushed concrete aggregate on the durability of structural concrete

The specification of crushed concrete aggregates (CCA) is increasing, particularly for low-grade applications, where quality is of less importance. In higher value applications, such as structural concrete, further research is required to understand the effect of CCAs on mechanical and durability performance. One disadvantage of using CCA is that the fine material (0-4mm) is often removed, which is not efficient. This research investigated the effect of fine CCA and its combination with coarse CCA in PC/GGBS structural concretes. The resistance to water and chloride ingress in terms of surface resistivity, sorptivity and rapid chloride migration were evaluated, together with compressive strength to determine compliance with characteristic and target mean strengths. From this limited study of CCA which forms a wider research project, the results indicate that a higher proportion of CCA, both fine and coarse, is detrimental to the resistance to water and chloride ingress, possibly due to the higher water absorption characteristics of the recycled material. The incorporation of GGBS however, significantly improves the durability performance, therefore making structural concrete with fine and coarse CCA a viable option.