Effect of water-to-binder ratio on chloride ion diffusion in concrete under continuous biaxial compression

Abstract

In practical engineering, chloride ions often attack concrete structures through non-uniform small regions, whose microstructure and stress forms are very complex and are usually influenced by the water-to-binder (W/B) ratio. In this paper, the chloride diffusion in concrete with three different W/B ratios under biaxial compression was tested, and the microstructure characterization and property analysis were carried out using digital image correlation (DIC), mercury intrusion method (MIP), and nanoindentation test. It was found that the chloride diffusion coefficient showed a trend of first decreasing and then increasing with the increase of biaxial compressive load, regardless of W/B ratios. A larger W/B ratio resulted in a larger porosity of concrete, poorer micromechanical properties of the interface transition zone, and a greater sensitivity to microcracks under load, thereby accelerating the chloride diffusion. Finally, a theoretical model considering the biaxial compressive stress level and W/B ratios was developed and effectively validated by the experimental results.