Visual and quantitative evaluation of crack bonding rate of self-healing mortars based on volumetric strain analysis

Self-healing concrete is an effective and environmentally friendly means of repairing concrete cracks and can effectively reduce carbon emissions. However, the crack bonding rate after self-healing has rarely been addressed due to the limitation of existing testing means. Therefore, this paper proposes an analysis method based on outputs from digital volumetric correlation (DVC) to visually and quantitatively evaluate the crack bonding rate of self-healed mortars. The method was applied to study the crack bond rate of mortars with different water-to-cement (W/C) ratios. The study showed that apart from strength recovery and crack sealing rates, the proposed scheme can effectively quantify the crack bonding rate that cannot be achieved by other methods. It was also found that the mortars with a higher W/C ratio had a higher crack bonding rate as more calcium hydroxide and carbonates were formed. In addition, the crack bonding rate (24.93%, 26.74% and 31.5%, respectively) was lower than the crack filling rate (37.3%, 38.4% and 45.4%, respectively) due to weak bonding behavior of some self-healing products.