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The effective mechanical properties of matrices healed by embedded microcapsules were investigated using Eshelby theory based on the microscale healing mechanisms, referring to the mechanical properties of the adhesive and the proportion of cracks that could be healed. This was determined by measuring the water absorption and vacuum saturation of precracked matrices. The microcapsules or cracks should not exceed 4 vol.% to ensure that approx. 90% of the modulus is retained even if the cracks cannot be reattached at all. Both the healed cracks and unhealed cracks contribute to the anisotropy, with a greater contribution from the unhealed cracks. The elastic modulus of the adhesive has a more significant influence on the anisotropy as the applied load increases. The measured stiffness recovery indicates that the cracks were only partially healed. This value corresponds to a healing efficiency index of 0.2–0.4 for the present conditions. [ABSTRACT FROM AUTHOR]

The effects of the addition of minerals of various compositions (i.e., silica-based materials, chemical expansive agents, swelling minerals and crystalline components) on the self-healing performances of cementitious materials were investigated. The self-healing capabilities were assessed by performing water permeability tests, quantifying the widths of the surface cracks and studying the water absorption of mortars that were pre-cracked by either splitting or compression. The results showed that the cracks that appeared early on healed more efficiently when they were cured in still rather than flowing water. High pHs and high temperatures accelerate crack healing. The healing efficiency can be further improved by utilizing a combination of minerals rather than a single mineral. A self-healing mechanism was discussed by combining these results with micro-observations. The precipitation of calcium carbonate, which is aided by higher pH values and higher calcium ion contents, was found to be the main contributor to the healing of surface cracks. [ABSTRACT FROM AUTHOR]

Highlights • The self-healing capability of steam-cured mortar was investigated for the first time. • AE signals can distinguish damage stage between healing products and host matrix. • The amount and energy of healing products can be qualitatively assessed by AE signals. Abstract The objective of this work is to investigate the self-healing performances of steam-cured mortars with mineral additives (e.g., calcium-based materials, chemical expansive agents and crystalline components). The self-healing capabilities of crack was evaluated by transport tests and acoustic emission (AE) analysis for cracked mortars. The two representative AE parameters, i.e., amplitude and energy, were used to reveal the characteristics of healing products. The results showed that the improvement of transport properties of cracked steam-cured mortars were more effective compared to standard-cured mortars. The healing efficiency can be further improved by utilizing mineral additives. The differences of damage stage between healing products and host matrix can be distinguished by AE signals. Upon reloading of steam-cured mortar with mineral materials, the number of amplitude were much larger and the cumulative energy was much higher compared to other mortar. It indicated that the steam-cured mortar with mineral materials possessed larger amount and much higher energy healing products in the crack to some extent, which were well consistent with that of transport properties and microscopic observation. [ABSTRACT FROM AUTHOR]