Effects of Magnesia Expansive Agents on the Self-healing Performance of Microcracks in Strain-Hardening Cement-based Composites (SHCC)

Abstract This contribution presents the self-healing performance of cracks in strain-hardening cement-based composites (SHCCs) containing different amounts of magnesia expansive agents (MEAs) with different reactivities. Specimens were preloaded under a four-point bending test to induce cracks and then exposed to water fog curing conditions. The changes in the crack width before and after curing were measured with a digital microscope, and a water absorption test was also performed to measure the sealing ability of the cracks. The test results show that three reactive MgO expansive agents can significantly improve the crack healing efficiency of SHCC under water fog curing conditions. However, the self-healing effect of the 10% dosage was not as good as that of the 5% dosage when the reactivity of the MEA was the same, and the MgO expansive agent with a reactivity value of 110 s shows the most promising effect on crack healing. Moreover, it should be noted that the 10% dosage was too high for the 110 s MgO expansive agent, resulting in poor volume stability.