Development of Self-Healing Ultra-High- Performance Concrete Using Smart Nanocapsules for Enhanced Structural Resilience

Abstract

Ultra-high-performance concrete (UHPC) is widely recognized for its superior mechanical strength and durability; however, its susceptibility to microcrack formation under mechanical and environmental loading poses a critical challenge to long-term structural resilience. This study presents the development of a self-healing UHPC system incorporating smart nanocapsules encapsulating a sodium silicate–based healing agent. The nanocapsules are synthesized using an in-situ polymerization technique and uniformly dispersed within the UHPC matrix without compromising workability. Mechanical performance, crack-healing efficiency, permeability resistance, and microstructural evolution are evaluated through compressive and flexural strength tests, water absorption measurements, scanning electron microscopy, and X-ray diffraction analysis. Experimental results indicate that the self-healing UHPC exhibits up to 85% recovery in flexural strength and significant crack closure for cracks up to 300 µm. The presence of nanocapsules enhances durability by reducing chloride penetration and water permeability. Microstructural observations confirm the formation of calcium silicate hydrate gels within healed cracks. The proposed smart nanocapsule-enabled UHPC demonstrates strong potential for autonomous damage mitigation, reduced maintenance requirements, and extended service life of critical infrastructure, contributing to sustainable and resilient construction practices.