Thermal Modeling of Mass Concrete Volumes Exposed to Cold and Hot Climates

Utilization of the high strength massive structures has recently increased. This naturally may lead to considerable thermal stresses which in turn create thermal cracks and reduce service life of the structures. Although many attempts, numerically and experimentally, have been to prepare a convenient solution for this problem however no agreement was obtained until now.
In the present research, slag and silica fume were used as a partial replacement for cement in the massive mixtures. Temperature history of the 10 concrete mixtures, with 0.44 water cement ratio, was determined via a semi adiabatic system. Concrete columns with 800 and 1200 mm dimension were modeled and a finite elements analysis was carried out to predict thermal stresses and risk of cracking during early stage. Furthermore, the concrete mixtures were examined under water-penetration test.
The results declare that using slag as partial replacement for cement diminished hydration peak temperature whereas, silica fume have no serious effect on this parameter. The lowest thermal gradient related to samples containing 50 and 65 percent slag with or without silica fume. The minimum risk of cracking were corresponded to the silica fume specimens. In conclusion using silica fume in concrete containing slag improve behavior of fresh and hardened concrete. The results of the present study showed that simultaneous usage of 35% slag with 10% Silica fume is considered as the best proportion in both strength, permeability and thermal properties