Factorial effects of mix design variables on the coefficient of thermal expansion of concrete mixtures

The coefficient of thermal expansion (CTE) is one of the most critical parameters for concrete pavement design. Concrete paving mixtures with high CTEs are generally subjected to temperature-related stresses and deterioration. In this study, a 2(k) design of experiment was applied to evaluate the effects of concrete mix design variables on the CTE of resultant concrete mixtures. Laboratory experiments were conducted by controlling six mix design variables, each at two levels, including aggregate type (granite or dolomite), fine sand type (manufactured or natural), fly ash type (Class C or Class F), cement content (314 or 273kg/m (3)), coarse aggregate content (1246 or 682kg/m (3)), and air content (3% or 6%). The respective and collective effects of these factors on the CTE were analysed. It showed that the type of coarse aggregate, fine sand, fly ash, and their respective contents are significant in explaining the variance of the lab-measured CTEs. The minimum CTE is a result of the concrete mixture consisting of low content of granite and cement in combination with high content of manufactured sand and Class F fly ash. To generalise the results, a parsimonious model was formulated and is capable of explaining over 92% of the total variance of the CTE and predicting it in a reasonably accurate manner.