Influence of Mineral Admixture on Early-Age Concrete Cracking

The research described in this paper is based on the theory of linear elastic fracture mechanics (LFEM) using the standard three-point notched bending beam for the double-K model. In this model, the value of initial fracture toughness and unstable fracture toughness are taken as the two key parameters to analyze the fracture process of concrete. These two parameters were obtained from the three-point bending tests employing the beams with initial notch to depth ratio of 0.3 at the ages of 1d, 3d, 7d and 28d. The results gotten from the test and analysis indicate that these two parameters of fly ash concrete are slightly lower than those of pure cement concrete. The two parameters of concrete with two kinds of mixture proportions increase observably as the age increases. The influence of fly ash on the initial fracture toughness and unstable fracture toughness are not such obvious as that on the compressive and tensile strength. The research results can provide a valuable reference in construction engineering.