Self-healing features in cementitious material with urea–formaldehyde/epoxy microcapsules

• A microcapsule designed for mechanics/permeability self-healing in concrete.
• Crack in concrete is filled by healing agent releasing from the microcapsules.
• Influence on the healing effect of mechanical properties/permeability is analyzed.

Urea–formaldehyde/Epoxy microcapsule is designed and prepared for the crack recovery of cementitious materials, using epoxy resin E-51 as a healing agent. The obtained microcapsules have an excellent surface texture (such as the roughness), suitable size and remarkable thermal stability. The viability of microcapsule during mixing process is investigated first. The breakage of microcapsules upon cracking and the crack-healing results are verified by SEM/EDS. Self-healing capacity is evaluated by crack-healing effect and mechanical property as well as chloride permeability. The experimental results reveal that the crack-healing ratios are in the range of 20.71–45.59%, indicating that the system actually work on the crack-healing. In addition, the healing ratio of compressive strength and impermeability is about 13% and 19.8%, respectively.