Modeling Concrete Thermal Expansion Based on the Packing Density Theory

Abstract

In this study, the effects of supplementary cementitious materials with changes in the structure of the concrete pores have been examined on the coefficient of thermal expansion (CTE) at different ages. The results indicated a descending trend for the CTE of the reference concrete up to 60 days (diminishing by about 12%), after which it remained constant. In contrast, an opposite trend was observed for the slag-containing concrete, i.e., the descending trend started after 60 days, and its CTE declined by 10% up to 120 days. In the following, two equations are presented for the concrete to estimate the CTE of the concrete during its lifetime based on its CTE at the age of seven days. Across all the concretes, the reduction of CTE was associated with lowered porosity. Moreover, evaluating the distribution of the pore size showed that when the pore diameter decreased, the CTE decreased as well, indicating a strong relationship between the median diameter of the pores and the CTE. Considering the fact that the concrete’s CTE depends on aggregates and the cement paste, a model was presented based on the CTE of the cement paste and its packing density to estimate the CTE of the concrete.