Evaluation on relationship between accelerated carbonation and deterioration of concrete subjected to a high-concentrated sewage environment

Abstract

Performance of concrete with different carbonation degrees subjected to a high-concentrated domestic sewage environment was studied to explore the relationship between concrete carbonation and concrete degradation. An accelerated carbonation method was adopted to obtain concrete specimens with various degrees of carbonation. The properties of the corroded concrete, including surface appearance, mass loss, mechanical strength and pH value as well as microstructure, were evaluated. It was found that the pH value of the carbonated concrete had an exponential function along with the carbonation depth, which can be considered as an index to present the change in the carbonation degree. Although concrete carbonation played a role to increase its compressive strength, the decrease in surface alkalinity of concrete accelerated the concrete deterioration when exposed to the sewage environment. With the increase of the carbonation degree, the strength loss of the corroded concrete increased gradually due to the seriously deteriorated microstructure. The sharp decrease in the content of element Ca on the surface layer of the carbonated concrete also indicated that the carbonation promoted the decalcification of hydration products and the generation of bio-acids. Furthermore, both the corrosion depth and the mass loss of concrete increased with the decrease of their surface pH values after exposure to the sewage, and there was a power function between the surface pH value and sewage attack extent of concrete.