Crack-Bridging Mechanisms in Elastic Polymer Coatings for Concrete Structures

Abstract

Crack formation in concrete structures is inevitable due to shrinkage, thermal movement, and structural loading. The ability of polymer coatings to bridge cracks without losing integrity is a critical performance indicator in construction applications. This white paper analyzes crack-bridging mechanisms from a polymer structure and morphology perspective.

Crack Formation and Stress Concentration

Concrete cracks introduce localized stress concentrations that rapidly propagate failure in rigid coatings. Conventional brittle polymer films fracture once strain exceeds a narrow tolerance window,  water ingress and accelerated degradation.

Polymer Design for Crack Bridging

Effective crack-bridging polymers share several structural characteristics:

• High elongation at break combined with elastic recovery

• Low glass transition temperature (Tg) for flexibility at service temperatures

• Controlled crosslink density to prevent permanent deformation

Ruico achieves these characteristics through butadiene-based elastomer segments, polyurethane soft segments, and optimized copolymer architectures.

Morphology and Film Formation

Crack bridging is not solely a function of bulk elasticity. Polymer particle packing, inter-particle coalescence, and interfacial adhesion to concrete surfaces are equally critical. Controlled emulsion morphology ensures uniform stress distribution across the film.

Construction Applications

• Roof waterproof coatings

• Bridge deck protective systems

• Exterior wall crack-resistant coatings

Conclusion

Crack-bridging performance must be engineered at both the molecular and morphological levels to ensure durable protection of concrete structures.

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