Abstract
There are limited studies about the effect of nanocomposite cementitious capillary crystalline waterproofing material (CCCW) on the self-healing properties of cementitious materials in different environments. Compressive strength recovery ratio(CSRR) test, electrochemical impedance spectroscopy (EIS) test, and macroscopic cracks healing observation test were adopted to study the self-healing properties of pure mortar specimens, mortar specimens mixed with CCCW, and nanocomposite CCCW respectively under three kinds of curing conditions. The self-healing mechanism of nanocomposite CCCW was analyzed using thermogravimetric analysis and differential scanning calorimetry (TG-DSC), mercury intrusion porosimetry (MIP), and scanning electronic microscope and energy dispersive spectroscopy (SEM-EDS) techniques. It was found that the curing condition significantly influenced self-healing performance, with touching water curing condition having the highest impact, followed by soaking water curing condition and natural curing condition. Nanocomposite CCCW promoted the healing performance of damaged specimens and significantly increased the CSRR. Under touching water curing condition, the CSRRs of the mortar groups with 3% nano-SiO2, 3% nano-CaCO3, and 2% nano-MgO were 26.1%, 11.5%, and 8.6%, respectively, higher than the CSRR of the single-doped CCCW group. After 28 days of touching water curing, change in charge transfer resistance before and after specimen healing (∆Rct) of the groups with 3% dosage of nano-SiO2, 3% dosage of nano-CaCO3, and 2% dosage of nano-MgO were 5.2, 1.8, and 2.7 times, respectively, higher than that of the single-doped CCCW mortar group. Throughout the healing process, the addition of the three nanocomposite CCCWs accelerated the hydration reaction to generate C-S-H gel, CaCO3, Aft, etc., improved the internal pore structure, reduced the size of the most probable pore diameter (MPPD) of the mortar specimens, and ultimately promoted the self-healing properties of the cementitious materials.
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