Ensuring thermal crack resistance of the bridge pier structure

Abstract

Introduction. In conditions of negative temperatures or in the absence of the possibility to optimize the composition of concrete during the period of strength gain of concrete monolithic reinforced concrete structures, the formation of thermal cracks is possible, the repair of which requires significant additional costs that are not provided before the start of work.The aim of the work is to reduce the cost of repairing these manufacturing defects in the form of pre-operational temperature-shrinkage cracks.Materials and methods. Cost reduction was achieved by assigning several options for concrete care, calculating the thermally stressed state of structures for each of the assigned options and choosing the optimal option for concrete care, providing minimal tensile stresses leading to the appearance of temperature-shrinkage cracks in structures, with the least amount, width of opening and depth of crack propagation.The calculation was carried out using modern calculation programs according to the methodology used in the NIIZHB named after A.A. Gvozdev, JSC Research Center of Construction.The features of the construction conditions were: concreting at a negative ambient temperature, the use of a concrete mixture with a cement consumption of 440 kg/m3; concreting the structure with sections 2.25–5.05 m high with an interval of 12 days between divisions; ensuring heat exchange of the structure with the environment in the initial period of 2–3 days after concreting and regulating the cooling rate of the structure using thermal insulation materials.Results. According to the results of the work, it was possible to practically eliminate the appearance of the defects in question and the cost of repairing cracks.Conclusions. The cost of work and repairs turned out to be about 10 times less than the estimated cost of repairing cracks that usually occur in similar structures and construction conditions.