Evaluation of compressive strength of hardening silica fume blended concrete

Silica fume (SF) is a byproduct of induction arc furnaces and has long been used as a mineral admixture to produce high-strength and high-performance concrete. Owing to the pozzolanic reaction between calcium hydroxide and SF, compared with Portland cement, the hydration of concrete containing SF is much more complex. In this paper, by considering the production of calcium hydroxide in cement hydration and its consumption in the pozzolanic reaction, a numerical model is proposed to simulate the hydration of concrete containing SF. The degree of hydration of cement and degree of reaction of SF are obtained as accompanied results from the proposed hydration model. Furthermore, on the basis of the volume stoichiometries, mixing proportions and the degree of reactions of cement and SF, the gel-space ratio of hydrating blended concrete is calculated. Finally, the development of compressive strength of SF blended concrete is evaluated through Powers' strength theory considering the contributions of cement hydration and SF reaction. The proposed model is verified through experimental data on concrete with different water-to-cement ratios and SF substitution ratios.