Improved chloride resistance of high-strength concrete amended with coal bottom ash for internal curing

•Chloride resistance of high-strength concrete was improved by using coal bottom ash aggregates.•Chloride did not readily diffuse to the cement paste in the vicinity of bottom ash.•Bound chloride per total chloride in the mortar was decreased when bottom ash was applied. The present work studies a chloride resistance of high-strength concrete incorporating bottom ash aggregates for internal curing. The chloride diffusion in concrete was evaluated by measuring the diffusion distance through steady-state and rapid-state penetration tests. The acid-soluble and water-soluble chloride contents in concrete were measured to evaluate the total and bound chloride concentrations in concrete. To detect the crystalline phase of hydration products that can bind chloride, a thermal analysis and an X-ray diffraction (XRD) analysis were carried out. In addition, the path of chloride penetration in concrete was analyzed by using an electron probe microanalyzer (EPMA). The results showed that, although there was no significant effect on the diffusion length, bottom ash in high-strength concrete can significantly reduce the amount of chloride diffusion.