Main reasons of reduction and determination of concrete foundations strength by methods of destroying and nondestroying control in buildings' construction and operation
The article is devoted to the main reasons of decreasing the bearing capacity and concrete' strength of buildings' foundations. The main defects and damages of foundation structures are given the reasons of which are: improper execution of construction and installation works, contravention of design solutions, contravention of the requirements for the maintenance of concrete during its hardening, increase in the load on the foundation until it reaches the design strength of concrete, not taking into account climatic conditions, lack of incoming control material. The main ways to eliminate these defects during scheduled repairs are to prevent the rapid growth of small cracks in concrete structures, to exclude the formation of corrosion in reinforcement, and to increase the protective characteristics of concrete. The article presents the main ways of determination of concrete foundations strength by destructive and non-destructive methods, as well as advantages and disadvantages of these methods. Presented classification of non-destructive methods and a modern instrument base for determining the strength characteristics of concrete foundations, also are given methods that are at the stage of experimental use. It is concluded that non-destructive testing methods have some advantages over destructive ones, as exclude the damage of structures, make it possible to track the process of concrete hardening, however, this methods have a high measurement error. The most accurate non-destructive testing methods are based on changing the ultrasound permeability in concrete or changing the amount of rebound of the striker from the concrete surface.