Mechanical and self-healing performance of rubberized calcium-sulfoaluminate-cement-based ECC for ultra-thin white-topping overlay use

To address the issues of cracks, joints, and vertical displacement caused by the long-term combined effects of aircraft and environmental loads, a novel early-strength Engineered Cementitious Composite (CSA-ECC) with self-healing capabilities has been developed. This composite incorporates recycled crumb rubber (CR) and is designed for use in ultra-thin white-topping overlay applications. The mechanical properties, self-healing behavior, and multi-scale microstructure of CSA-ECC at different curing ages were analyzed through compression, tensile, flexural, and wet-dry cycling experiments, as well as scanning electron microscopy (SEM), using two different CR particle sizes and replacement rates. The feasibility of this material for ultra-thin white-topping applications was investigated. The results indicate that the addition of CR significantly improved the bending deformation capacity of CSA-ECC. At 3 days, the deflection increased by 1.24–1.43 times compared to the reference mixture (M0), which exhibited a deflection of 5.91 mm. Although the incorporation of CR reduced compressive and flexural strengths, the minimum values at 3 days still exceeded the requirements for airport pavements, reaching 32 MPa and 6.43 MPa, respectively. Furthermore, the inclusion of CR reduced crack widths and improved strain capacity by 80 %. These improvements contribute to the high ductility and crack resistance required for seamless pavement applications. In addition, after 15 wet-dry cycles, small cracks in the CR-containing CSA-ECC mixtures were almost completely sealed, with the healing products primarily consisting of dense crystals of C-S-H and CaCO₃. These findings suggest that CSA-ECC with CR is highly suitable for ultra-thin white-topping applications in airport pavements, and the study holds significant implications for promoting sustainable airport pavement construction and the development of CSA-ECC materials.