Thermal Conductivity of Hydrated Paste in Cement-Based Foam Microstructure

This article presents the thermal constants of hydrated cement paste, which constitute the air-void wall of cement-based foam microstructure, and examines its influence on moisture, age, pozzolanic admixture type, and content. Along with the reference mix, containing portland cement only, six other mixes were prepared by replacing cement with fly ash, silica fume, and metakaolin, up to 20% by mass in the binder. The Transient Plane Source, a thermal analyzer that conforms to ISO test standards, was employed to evaluate the thermal constants. Here, the measurements were made at 60, 120, 210, and 300 days. The results revealed that the drop in thermal conductivity for the cement paste was significant in the earlier age but progressively became insignificant as the hydration advanced. It was also found that adding fly ash and silica fume in higher dosages resulted in reducing the conductivity, while metakaolin exhibits a reverse trend. Furthermore, the reduction in the moisture content due to pozzolanic admixture was also noticed. Finally, an empirical formulation was developed to predict the thermal conductivity of the hydrated cement paste, which was also validated against the results of past research.