The article deals with heat liberation of barium cements, which influences the crack formation in mass concrete structures. The results of heat release and physical testing of barium cements with a different content of BaO are presented in this paper. The strength of cement and its setting time will decrease significantly, if the content of BaO in clinker is high (about 47%). This cement is characterized by a low water requirement and heat liberation. Properties of cement with a low content of barium oxide (5.5%) are close to the properties of the standard Portland cement. In this case heat liberation is low in the initial period of hardening, but at the later stage it exceeds the exotherm of a reference sample. A small amount of BaO in cement clinker reduces the exothermic effect and increases the thermal crack resistance of concrete.

The article considers the problem of the formation of temperature and cracks in a reinforced concrete floor in thin 400 mm, connected by reinforcing outlets with internal reinforced concrete walls and the outer ring wall of the core of a high-rise building. During the hardening of the laid concrete, the formation of through cracks in the overlapping, extending from the walls and located across the corridor formed by the walls, was observed. The paper analyzes the possible causes of cracking. Cracking occurs due to the restriction of free temperature and shrinkage deformation of the floor slab by a rigid connection with the walls. The direction of the cracks indicates that tensile shrink stresses act along the walls. Cracks form during the cooling of the concrete floor, when the directions of the vectors of shrinkage and thermal deformation coincide. The work gives recommendations for the care of concrete floor structures.