Potential of sodium sulfate solution for promoting the crack-healing performance for strain-hardening cementitious composites

Abstract

Strain hardening cementitious composites (SHCCs) have been shown to have promising self-healing ability. Nevertheless, reliable healing performance only occurs for micro-cracks in relatively young SHCCs and requires several months of moisture exposure. To overcome these criteria for effective healing, this study explored the feasibility of using sodium sulfate solution to promote the healing performance of medium-term SHCCs. For this purpose, cracks were induced in SHCC specimens at the age of 180 days followed by a 28-day exposure to high sulfate ion concentrations. Four SHCC mixtures with different ratios of cement replaced by pozzolans were tested. In particular, the performance of the SHCCs containing an extremely high volume of granulated blast-furnace slag (GGBS) was studied. The healing behavior of the SHCCs was evaluated via multiple means, including uniaxial tensile tests, monitoring of the crack width, scanning electron microscopy, and energy dispersive x-rays. The results indicated that short-term exposure to sodium sulfate solution effectively promoted the healing performance of cracked SHCCs, especially for cracks with relatively larger widths. It was found that the newly formed healing precipitation within the cracks primarily consisted of calcium carbonate, calcium silicate hydrates, and ettringite. In addition, the SHCCs with 71% replacement of cement by GGBS had the highest recovery in terms of crack width and tensile response.