Mechanical behavior and self-healing mechanism of force-chloride ion triggered double-walled microcapsule/cement-based composites

•The force-chloride ion triggered double-walled microcapsules were prepared by interfacial polymerization method.•The mechanical self-healing properties of the cementitious composite were studied.•The microcapsule has a force-chloride complex response mechanism.•The critical stress of inner core and outer core of double-wall microcapsule is 9.2 MPa and 8.4 MPa respectively. The force-chloride ion triggered microcapsules with PbSO4 embedded on the wall material were successfully synthesized by a two-step interfacial polymerization method. The structure and properties of the microcapsules were characterized, and the self-healing properties of cementitious composites were studied from the aspect of mechanical properties. The results showed that the microcapsules synthesized are suitable in morphology, the average particle size being 53.8 μm. Fourier Transform Infrared Spectrometer (FT-IR) showed that the structure of the microcapsule with double-core and double-walled has been formed. Scanning Electron Microscopy (SEM) and Energy Dispersive Spectrometer (EDS) confirmed that PbSO4 was successfully embedded on the capsule wall, and the microcapsules were suitable in the performance triggered by force-chloride ion. Moreover, the strength recovery rate of cementitious composites with 3% microcapsules could gain up to 84%. The microcapsules can survive in the cement mixing process and be evenly distributed in the matrix. Digital Speckle Correlation Method (DSCM) was used to track the deformation behaviors of self-healing cementitious composites during the loading procedure, obtaining the self-healing mechanism based on filling cracks, limiting cracks’ development, and healing cracks from the variation of stress–strain, distribution of strain field and eigenvalue StC and Sts.