HEAT DISSIPATION AT CEMENT HARDENING

Abstract

During the construction of concrete structures of small cross-sections, the release of heat during cement hardening has no harmful effects. With the increasing temperature of the hardening cement mass, the rate of cement hydration increases. This increases the rate of release of its heat of hydration of cement. The consequence of the accelerated process of hydration of the binder is a more intensive increase in the strength of cement stone than in the case of hardening under normal conditions. This fact is widely used in practice for the intensification of the hardening of concrete. When structures with small cross-sections are being built, the heat released during hardening is relatively quickly transferred to the surrounding space and does not cause a significant increase in temperature. In structures made of massive concrete (with a large cross-section), this heat is stored in the interior of the array for a long time, which causes a rather large rise in temperature and its slow drop. This is due to the fact that heat transfer to the external environment is hampered here by the considerable thickness of the massif and the rapid rate of concreting, mechanized laying of large masses of concrete. As a result, a temperature difference is created between the internal and external parts of the structure and harmful internal stresses arise that can cause cracking in the hardened concrete. This leads to a violation of its solidity. The faster cement hydrates, the sooner and more heat is released. The types of cements with a high content of tricalcium silicate and aluminate emit more heat and rather than types of cement with a high content of dicalcium silicate and tetra-calcium aluminoferrite. However, the latter has a lower strength. The increase in strength resulting from the hydration process is inevitably associated with the release of heat into the environment.