[Geotechnical Engineering]

Zhang, Z. Y., Jin, X. G., Luo, W. Long-term behaviors of concrete under low-concentration sulfate attack subjected to natural variation of environmental climate conditions[J]. Cement and Concrete Research, 2019, 116: 217-230.

Keywords: Long-term Behaviors, Concrete, Durability, Sulfate Attack

Abstract:

Accelerated laboratory tests on resistance of concrete exposed to sulfate attack have generally been conducted in high-concentration solutions or under drastic drying-wetting cycle conditions. However, these accelerated regimes radically alter the nature of sulfate attack mechanisms on concrete under real field exposure. To obtain reliable information on the long-term behaviors of concrete under real field conditions, the behaviors of concrete samples under three different exposure regimes, i.e., full immersion, full immersion with general use drying-wetting cycles and full immersion with natural drying-wetting cycles (field-like condition), were investigated in this research. Meanwhile, three different concentrations of sulfate sodium solutions, i.e., 0 % water for control, 2.1 % for field-like condition and 15 % for high-concentration condition, were considered. Physical and mechanical properties, such as mass, expansion, permeability and compressive strength, were tested at regular time intervals during whole exposure period to describe the associated evolution laws. Results of this study showed that the exposure regime of full immersion with natural drying-wetting cycles can well reproduce the field exposure condition of concrete under certain sulfate-rich environments. Both concentration and exposure type affect the nature of sulfate attack mechanism on concrete, along with the evolution of physical and mechanical properties. A two-stage evolution model was found in the evolution of concrete samples in high-concentration solutions or under general use drying-wetting cycles, while a three-stage evolution model consisting of the enhancement stage, the incubation stage and the degeneration stage, was observed under the field-like exposure condition. Compressive strength was found to be sensitive at the enhancement stage, while permeability is sensitive at the final degeneration stage.