Should Minimum Cementitious Contents for Concrete Be Specified

Minimum cementitious contents are commonly specified in project specifications. The primary focus of this study was to examine the influence of the cementitious content on concrete performance at specific water-to-cementitious materials ratios. The experimental variables included water-to-cementitious materials ratios ranging from 0.40 to 0.55, mixtures containing portland cement only, and mixtures containing 40% slag cement or 25% fly ash. Concrete performance was evaluated through laboratory tests on workability, strength, and durability. The results showed that at a given water-to-cementitious ratio a higher cementitious content results in higher paste volumes and poorer concrete performance. On the basis of these results the value of maintaining minimum cementitious content requirements in project specifications is questioned.