Unsteady Temperature Fields in the Calculation of Crack Resistance of Massive Foundation Slab During the Building Period

Abstract

The main technological requirement for massive slabs concreting is the continuity of laying at full height. This method is the fastest and most profitable from an economic point of view. In this case, the exothermal reaction of hardening of the concrete mixture leads to the uneven distribution of temperatures in the block, the appearance of tensile stresses on the surface of the structure and the temperature cracks formation. There are a significant number of methods and programs for calculating the thermal stressed state of massive concrete structures in the building period. However, the majority of methods do not consider factors such as the effect of hardening temperature on the thermophysical and deformation characteristics of concrete, the influence of fluctuations in air temperature. Thus, at present, methods for calculating the thermal cracking resistance of massive concrete and reinforced concrete structures are insufficiently developed and remain relevant, and require further development. The article presents a methodology for calculating thermal cracking resistance in a massive concrete structure, with one-dimensional setting, during construction. The developed methodology considers the dependence of heat release and concrete characteristics on the “temperature” history of hardening, using the example of the foundation slab of the reactor compartment of LNPP-2. The task is to select the optimum insulation thickness in terms of providing thermal crack resistance of the plate when calculating by average monthly, average daily and hourly air temperatures. This clearly shows the limits of applicability of the studied methods.