Modeling concrete thermal expansion based on packing density theory

This study investigated the effects of supplementary cementitious materials with changes to the structure of the concrete pores based on 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 (decreasing by about 12%), after which it remained constant. On the contrary, a different trend was observed for the slag-containing concrete; in other words, the descending trend started after 60 days and its CTE declined by 10% up to 120 days. In the following, two equations for the concrete were presented to estimate its CTE during its lifetime based on its CTE at the age of seven days. In all concretes, the CTE reduction was associated with the reduced porosity. Moreover, the results of evaluating the pore size distribution showed that with a decrease in the pore diameter, the CTE decreased as well, indicating a strong relationship between the median diameter of the pores and the CTE. Given that the CTE depends on the aggregates and cement paste, a model was proposed based on the CTE of the cement paste and its packing density to estimate the CTE of the concrete.