EFFECTS OF SILICA FUME ON CRACK SENSITIVITY

The sensitivity of concrete to cracking is a complex interaction between structural geometry and several material properties during the hardening process. This paper describes an investigation that was conducted to assess the crack sensitivity of high-performance concretes with different silica fume contents (0%, 5%, or 10%). First, the material properties, including heat development, coefficient of thermal dilation, autogenous shrinkage, mechanical properties and relaxation behavior of these concretes, were determined under isothermal and semiadiabatic conditions. This data was then used to rate crack sensitivity by calculating the ratio of self-induced stress to strength over time under a variety of external conditions. Results show that the effects of variations in silica fume content are of minor importance compared with other factors such as cement type, water-cementitious materials ratio, structural configuration, degree of insulation, and environmental conditions. No single concrete property should be used to assess cracking risk since, in practice, the interaction between several properties over time defines the risk.