Synthesis and characterization of a new polymeric microcapsule and feasibility investigation in self-healing cementitious materials

•PF/DCPD microcapsules were prepared via in situ polymerization.•The mean diameter and size distribution of microcapsules could be controlled.•The microcapsules possess good chemical stability in cementitious materials.•XCT was used to visualize the distribution and rupture process of microcapsules.•The microcapsules have a good dispersibility and trigger sensitivity to the cracks. This paper presents work towards development of a new type of polymeric microcapsule with phenol–formaldehyde (PF) resin as shell and dicyclopentadiene (DCPD) as healing agent for self-healing microcracks in cementitious materials. The PF/DCPD microcapsules were synthesized via in-situ polymerization and characterized by means of optical microscope (OM), scanning electron microscope (SEM) and thermal analysis (TGA). The chemical stability of synthesized microcapsules and the trigger performance were studied respectively in simulated concrete pore solution and hardened cement paste specimens. The results revealed that the synthesized microcapsules possessed excellent stability in both simulated pore solution and real cement environment. X-ray computed tomography (XCT) was applied to observe the status and fracture behavior of microcapsules inside cement paste matrix. Further segmentation and 3D rendering of the reconstructed data obtained from XCT showed that the microcapsules had a good dispersibility with desired trigger sensitivity. The OM investigation of a fractured surface of a cement paste incorporated with microcapsules confirmed that the self-healing function of the microcapsules could be triggered by cracking and the healing agent could be released simultaneously to heal the cracks.