Experimental and Numerical Analysis of Interfacial Cohesive Parameter Sensitivity in Self-healing Concrete: Optimization of Microcapsule Size and Dosage

The advancement of finite element technology has facilitated the numerical simulation of interfacial behavior in self-healing concrete. Although the cohesive zone model (CZM) has been introduced in previous studies, most rely on empirically assigned parameters and lack systematic sensitivity analyses of the cohesive properties at the microcapsule–cement interface. This study focuses on self-developed polyvinyl alcohol - shelled microcapsules, which were integrated into a three-dimensional mesoscale finite element model using cohesive zone theory and a random packing algorithm to simulate uniaxial compression. For self-healing concrete containing 10% microcapsules (2.36–3.20 mm), cohesive parameters were calibrated through orthogonal testing and identified normal and tangential traction as the dominant factors affecting mechanical performance. Subsequent single-factor analysis identified 1.5 MPa (normal) and 6 MPa (tangential) traction as the optimal parameters, leading to a 21.7% increase in cracking load and a 14.2% reduction in crack area relative to the initially calibrated values. Additional analysis showed that smaller capsules formed thicker shells under identical spraying conditions, enhancing bonding with the cement matrix. Combined simulation and experimental results confirmed that both particle size and dosage negatively correlate with compressive strength. Optimal performance was achieved at 5%–10% dosage with 1.6–2.36 mm capsules, whereas excessive dosage (>30%) severely degraded structural integrity. These findings provide valuable insights for the modeling and design of self-healing concrete.