Encapsulation of aliphatic amine TEPA for self-healing cement paste

Cracks are inevitable during the service of cement-based facilities. The application of microcapsule technology to cementitious materials has realized the self-healing of cracks. In this research, tetraethylenepentamine (TEPA) was successfully encapsulated with polyethylene glycol (PEG)/polyurea shell by integrating melting-dispersion-condensation and interfacial polymerization method. The average diameter of final microcapsules prepared at 300 RPM was 666.9 ± 345.8 μm and the shell thickness was 45.5 ± 1.6 μm. The final microcapsules demonstrated good dispersibility and thermal stability. The normalized strength of the final microcapsules ranged from 0.6 MPa to 1.0 MPa. Moreover, the final microcapsules could remain stable completely both in ambient water and saturated calcium hydroxide (Ca(OH) 2 ) solution for 12 h. Additionally, the final microcapsules remained integral structure during mixing with fresh cement paste and were uniformly dispersed in the hardened cement paste. When microcapsules dosage was 3.0 wt%, the compressive strength of 28 days exceeded 50 MPa and the self-healing rate of compressive strength reached the highest, up to 27.5%. After self-healing, specimens containing microcapsules exhibited excellent resistance to water penetration. The single microcrack of self-healing cement paste with hydration ages of 7 days, 28 days, or even 56 days could be repaired to varying extent and the maximum repairable microcrack width was 145.6 ± 21.6 μm.