What innovations allow concrete to self-heal minor cracks outdoors?

Concrete is a fundamental material in construction, but cracks can compromise its durability. Recent innovations have introduced self-healing concrete technologies that autonomously repair minor cracks outdoors, extending the lifespan of structures. Key methods include:

1. Bacterial Healing: Microorganisms like *Bacillus subtilis* are embedded in concrete. When water enters cracks, these bacteria produce limestone, sealing the gaps.

2. Encapsulated Polymers: Tiny capsules containing healing agents (e.g., epoxy) break upon cracking, releasing the material to bond cracks.

3. Shape Memory Alloys: Embedded wires contract when heated, closing cracks mechanically.

4. Carbonation: Exposure to CO₂ triggers calcium carbonate formation, filling micro-cracks naturally.

These advancements reduce maintenance costs and enhance sustainability, making self-healing concrete a game-changer for outdoor infrastructure.