Chloride corrosion resistance of manufactured sand reinforced concrete prepared in plateau environment

Abstract

The durability of manufactured sand concrete prepared in a simulated plateau environment was investigated. Several factors, such as preparation environment of the specimens, concrete strength and corrosion rate of steel bar, were considered in this study. In these experimental investigations, the accelerated corrosion test on specimens exposed to a chloride salt solution and thereafter the static tensile test on corroded steel bars retrieved from these specimens were carried out. The durability of different specimens was compared by analyzing the surface crack development on the concrete surface, the corrosion morphologies of embedded steel bars, the degradation of mechanical properties of steel bars, and the concrete microstructure. In addition, the differences observed in the crack development of concrete and the degradation of mechanical properties of corroded steel bars between plateau and normal exposure environments were quantified. The results show that the steel bars embedded in the specimens prepared in a simulated plateau environment are prone to non-uniform corrosion attack, especially for the specimens with low concrete strength. The preparation environment of specimens and concrete strength have little influence on the degradation of mechanical properties of steel bar when subjected to a theoretical corrosion rate less than 6 %. Compared with the specimens prepared in a normal environment, the yield strength, ultimate strength and elongation of corroded steel bars subjected to a theoretical corrosion rate in the range 2∼10 % in specimens prepared in a plateau environment decrease by 2.99 %, 4.44 % and 14.78 % on average, respectively. For the specimens prepared in a plateau environment the decreased durability of concrete is explained by insufficient hydration and low compactness inside concrete, so that it is easier for chloride ions to penetrate into concrete, resulting in early corrosion. As a result, the variation of average crack width of concrete with actual corrosion rate and the variation of nominal yield and ultimate strengths of steel bars with their maximum section loss rates no longer satisfy the linear relationship for the specimens prepared in plateau environment, which is different from the specimens prepared in a normal environment. Moreover, the protective effect of concrete on embedded steel bar can be significantly enhanced by improving the strength of concrete produced in a plateau environment.