This study evaluates polyurethane-shelled microcapsules containing a commercial water-repellent agent as an autonomous self-sealing system for concrete in aggressive environments. Microcapsules were synthesized via membrane emulsification and interfacial polymerization, yielding a D50 of 77 μm and sufficient integrity for concrete incorporation. An optimization study identified 2 by weight of cement (bwoc) % as the optimal dosage, balancing hydrophobic performance and mechanical properties. Cracked (100 and 300 μm) and uncracked specimens were exposed to freeze–thaw cycles with de-icing salts, artificial seawater, and a chloride-rich solution. Capsule rupture upon cracking hydrophobized the crack walls, resulting in sealing efficiencies of up to 96% for 300 μm cracks. Freeze–thaw exposure reduced scaling by up to 74%, while marine exposure lowered chloride ingress through cracks by up to 37%. Limited effects were observed under chloride-only conditions, highlighting exposure-specific performance. Overall, polyurethane microcapsules act as an effective self-sealing system, enhancing concrete durability in an environment-dependent manner. The graphical abstract illustrates how polyurethane microcapsules embedded in concrete rupture when a crack (100–300 μm) forms, releasing a water-repellent agent that hydrophobizes the crack surfaces. The cracked concrete is then exposed to freeze–thaw with de-icing salts, marine, and chloride-rich environments. The released agent promotes crack sealing and strong hydrophobic behavior (contact angle >100°), enhancing the concrete’s durability under these aggressive conditions. • Polyurethane microcapsules enabled autonomous crack sealing under aggressive exposures. • Crack-triggered release of water repellent reduced moisture uptake and frost salt scaling. • Microcapsules limited crack-driven chloride ingress in marine and freeze–thaw conditions. • Self-sealing performance depended mainly on crack width and exposure conditions.
Cappellesso et al. (2026) studied this question.