CARBONIZATION OF CONCRETE AND CORROSION OF REINFORCEMENT OF REINFORCED CONCRETE STRUCTURES OF UNDERGROUND SEWERAGE SYSTEMS

Abstract

The process of carbonization of concrete with different ratio of water to cement (W/C) was studied, and the influence of the environment on corrosion damage of reinforced concrete reinforcement was studied. The results of the study of carbonization of concrete on specially prepared model samples of concrete with a size of 250x250x250 mm with an exposure period in NACE solution for 500 days without external load are presented. Measurements of corrosion damage of reinforcing rods, which were placed inside concrete cubes, were performed. The method of estimating the amount of carbonization of concrete and corrosion of reinforcement is described in detail in known scientific papers. The obtained data testify to the active carbonization of concrete during the whole exposure period of the samples in NACE solution, however, concrete prepared at the ratio W/C = 0.5 and 0.6 is particularly significant in terms of carbonization intensity. Concrete with a ratio of W/C = 0.7 is less susceptible to damage. Moreover, a similar trend is observed for corrosion of fittings. This is due to the fact that the increase of the aqueous medium in the concrete mass facilitates diffusion processes of delivery to the reactive zone of chemically aggressive ingredients such as carbon dioxide, chloride ions, hydrogen, sulfur, sulfate ions, various types of bacteria and the like. The kinetics of concrete carbonization and corrosion of reinforcing bars in chemically aggressive NACE medium depending on the exposure period of the samples in the model solution was experimentally studied. It is established that with the increase of the water-cement ratio W/C from 0.5 to 0.7, the depth of carbonization and the layer thickness of corrosion products increase sharply. The flooding of the surface layers of the reinforcement and their strong embrittlement in the process of long-term operation of the reinforcement in the structure of reinforced concrete, which causes a decrease in crack resistance in general of reinforced concrete structures. The degradation of reinforcing steel during long-term operation in aggressive environments, which leads to premature corrosion damage to the reinforcement with subsequent destruction of the structure, was investigated experimentally with the involvement of high-precision metallographic equipment.