A Molecular Velcro Self-Healing Cement

Cement, a fundamental component in concrete infrastructure, is inherently susceptible to cracking and degradation. Conventional self-healing strategies—whether intrinsic or extrinsic—often suffer from limited healing agent availability, reduced mechanical integrity, and high cost. In this study, we present a novel, trace-concentration (<0.15 wt%) polymer-modified cement that exhibits robust, multi-cycle autonomous healing capabilities without the use of expensive encapsulation or microchannels and without compromising initial mechanical performance. This material operates via dynamic, reversible chemical interactions between the cement matrix and an engineered polymer complex, mimicking the behavior of a 'molecular Velcro'. The polymer actively senses, migrates to, and heals cracks through a combination of electrostatic and hydrogen bonding between polymer-polymer and polymer-cement interfaces. Mechanical testing revealed recovery of compressive and tensile strengths of up to 62% and 59%, respectively, as well as sustained recovery exceeding 40% and 25% across multiple damage-healing cycles. Critically, this high-performance healing is achieved with negligible impacts on workability, setting time, and hydration dynamics. The integration of a spontaneous, vascular-like, polymer delivery mechanism with reversible chemical bonding offers a transformative pathway toward cost-effective, durable, and sustainable infrastructure materials.