Strengthening of reinforced concrete structures by composite materials taking into consideration the carbonization of concrete

One of the main causes for deterioration of reinforced concrete structures in modern construction is corrosion of reinforcement. Corrosion leads to decrease of adhesion between reinforcement and concrete, formation of cracks and destruction of the protective layer of concrete. All this reduces the load-bearing capacity of reinforced concrete structures. The structures of sludge reservoirs exposed to carbon dioxide were used as an object of the study. The characteristic defects and damages revealed by visual inspection were described. The verification calculation of the considered construction depending on the pH of the medium was performed on the basis of the results of technical inspection and study. The degree of carbon dioxide impact on the considered structures was determined by the phenolphthalein test method, which is based on the color change of acid-base indicator solution on the surface of concrete and reinforced concrete depending on the pH value of its medium. The phenolphthalein test revealed that pH of the medium is less than 8 for the depth more than the thickness of the concrete protective layer. A verification calculation of the considered structure was performed on the basis of the technical inspection results and the conducted research. According to the calculation results, a variant of beam reconstruction and strengthening using external reinforcement based on carbon fibers FibARM 230/150 was proposed. The reconstruction was carried out with account of the carbonized concrete layer.