ABSTRACT
In a recent Concrete Society technical report (No.29, 1987) it was pointed out that changes in cement properties had resulted in the strength of standard concrete mixes tested at the BRE increasing from ~30 MPa in 1950 to ~45 MPa in 1980. This implies that concretes designed to specified strengths will currently have lower cement contents and higher water/cement ratios than they did in 1950. It has been argued that the improvements in cement strengths may thus have led to the production of less durable concrete. The Concrete Society report identified an increase in cement C3S content as the most notable change in the physical and chemical properties over the same period. This historical link between increasing cement C3S content and a perceived decrease in concrete durability has resulted in the development of the idea that high cement C3S content leads directly to reduced concrete durability.
