Concrete heat liberation in thermal stressed state analysis

This paper presents the results of numerical studies of the temperature regime and the thermal stressed state of the reinforced concrete wall of the nuclear power plant foundation block during the construction period with continuous concreting at full height. Calculations were done both using the dependence of the change in heat liberation over time on the hardening temperature, according to the theory of I.D. Zaporozhets, as well as the experimental data. It is established that if Zaporozhets equation is used in calculations, the correction of heat release values should be performed in the first 45 hours of concrete hardening. In order to correct the theoretical values of the specific heat, the last one should be multiplied by the correction factor. The dependence of the factor on the time within the range of 4 to 45 hours is approximated with sufficient accuracy by the obtained fifth degree polynomial. The crack resistance of the structure was determined using a deformation criterion, taking into account the change in the ultimate elongation of concrete over time. In this particular case of concreting a structure it is shown that when the correction function is introduced into the calculation program there is no need to use thermal insulation. The direct economic effect, as well as the indirect one associated with the decrease in the construction period, allow avoiding the rise of the construction costs. It is proposed to use the developed methodology in practical calculations of thermal crack resistance of massive concrete and reinforced concrete structures during the construction period.