INSPECTION OF A MONOLITHIC REINFORCED CONCRETE SLAB WITH CRACKS

Abstract

Regulatory documents state that the formation of cracks is normal for reinforced concrete structures and should be limited to the level at which the cracks do not affect the proper functioning of the structure or they are acceptable. Cracks is reduced the quality of concrete, its strength and durability, so it is needed to minimize their formation and opening. The occurrence of cracks in reinforced concrete monolithic structures is analyzed in the work. Field inspections of the monolithic slab of the new construction’s third floor of a multi-storey residential building were performed. Visual inspection revealed a number of through cracks in the monolithic floor, which appeared after the rainstorm. During the inspection, a characteristic cracks propagation of force origin on the lower surface of the slabs was noticed, while the crushing of the concrete of the compressed zone was not recorded. The reasons for the occurrence of through cracks could be: a violation of the technology of monolithic reinforced concrete structures; too early loading of a slab by concreting of the next floor is possible; the external temperature is not taken into account when hardening the concrete of the floor slab. In addition to the visual inspection of the structure, the compressive strength of the slab was determined by the non-destructive method with a Schmidt sclerometer (hammer). In the laboratory, concrete samples were tested according to standard methods, the compressive strength of concrete for 6 days was set, which corresponds to class C20/25. It was recommended: 1) to perform point loading with a payload at the characteristic points of the specified floor slab of the 3rd floor with the installation of crack meters and check the deflections of the floor slab in accordance with the requirements of DBN V.2.6.-98:2009 (2.2.2.3) to identify the possibility of its further operation; 2) perform reinforcement of the floor slab of the 3rd floor, the proposed options should be agreed with the design organization.