Re-evaluation of Strength and Stiffness Relationships for High-strength Concrete

It has been generally accepted that the tensile strength and elastic modulus of concrete is proportional to the square-root of its compressive strength. This relationship, however, may not be applicable for high-performance concrete. The study presents data on strength and stiffness of concretes containing a laboratory produced metakaolin and commercial silica fume as cement replacement materials, with water-to-cementitious materials ratio of 0.27 to 0.33. Approximately 750 specimens were tested and compressive strength of up to 110 MPa at 90 days were reported. Analysis of the best-fit relationships for tensile-compressive strength and stiffness-compressive strength found that the square-root function recommended by most codes of practice is inadequate when applied to concretes of higher strength, particularly in the case for tensile strength prediction.