Thermal Diffusivity of Concrete as a Composite Material

Concrete can be regarded as a composite material composed of cement paste or mortar as a matrix and gravel as an aggregate. Thermal diffusivity is a measure of material's ability to undergo a temperature change. In this study, the thermal diffusivity of concrete was measured and the results were examined from the viewpoint of a composite material.When both of the fine and the coarse aggregates are of the same rock type, the diffusivity of the concrete shows a tendency to increase with increasing the aggregate content. When they are different, however, such tendency no longer exists. Hence the rock type is one of the most important factors which determine the diffusivity of concrete.Since the exact value of diffusivity of aggregate is generally unknown, a model coarse aggregate was made of the mortar of known diffusivity and was used to make concrete samples. The measurement of the diffusivity on these samples showed that the diffusivity of concrete can be expressed in terms of the diffusivities and the volume fractions of the constituent materials. This result can be used to estimate an unknown diffusivity of aggregate, mortar or concrete when two of these three quantities are known.