High-Performance Self-Stratifying Fiber-Reinforced Mortar for Airport Pavement Thin-Layer Repair: OPC-SAC Hybrid System Optimization

Concrete airport pavements are prone to surface damage under the coupled effects of environmental exposure and mechanical loading, where thin-layer repair can rapidly restore operational capacity. Inorganic repair materials based on ordinary Portland cement and sulphoaluminate cement (OPC-SAC) suffer from excessively rapid initial setting and inadequate deformation resistance. This study developed a novel self-layering fiber-modified OPC-SAC repair mortar that combines high fluidity, high early-age strength, appropriate setting time, and stratified fiber distribution. Results demonstrate that polycarboxylate superplasticizer (PCE) and sodium gluconate (SG) effectively regulated mortar fluidity and setting time. A CaO dosage of 3 wt% produced the highest 2 h flexural and compressive strengths of 7.0 and 40.0 MPa, respectively, corresponding to increases of 62.8% and 81.8% compared with the CaO-free mortar. Although fiber incorporation reduced fluidity, increasing the proportion of steel fibers in the hybrid system alleviated this reduction and improved the mechanical properties and toughness. At a total fiber volume fraction of 1.5% and a PP-to-steel-fiber ratio of 1:3, the mortar maintained a fluidity of 285 mm and achieved 28 d flexural and compressive strengths of 13.8 and 103.1 MPa, respectively. This mixture also exhibited a favorable combination of stiffness, toughness, and strain-hardening behavior, together with a self-stratifying fiber distribution. The optimal mixture was therefore determined as 0.4 wt% PCE, 0.13 wt% SG, 3 wt% CaO, and 1.5 vol% total fibers with a PP-to-steel-fiber ratio of 1:3. This research provides a high-performance material solution for rapid airport pavement repair.