Role of cement content in specifications for concrete durability: aggregate type influences

In this paper, the second of the series, examining the role of cement content in specifying concrete durability, the influences of aggregate characteristics are considered. As for the first paper, the reported work was carried out within a framework of mix adjustments, required to produce practical concretes, that is, with the inclusion of filler and superplasticising admixture. A total of five UK normalweight aggregates and a lightweight aggregate were examined. It is shown that, for a given w/c ratio and aggregate type, reduction in cement and water contents (and the associated mix adjustments) did not adversely affect concrete properties (fresh, bulk engineering, permeation and durability). Indeed, many aspects of concrete performance were enhanced, with the improvements with cement reduction generally being greatest for aggregates having low absorption. Furthermore, the influence of cement content at a given w/c ratio on durability was found to be less significant than that of a change in aggregate type for the range of UK materials tested. The implications of the study for concrete construction practice are discussed.