Assessment of impact resistance recovery in Ultra High-Performance Concrete through stimulated autogenous self-healing in various healing environments

Ultra High-Performance Concrete (UHPC) is widely acknowledged for its remarkable mechanical properties, owing to its compact microstructure. The response of UHPC to impact forces plays a vital role in ensuring the safety and longevity of structures, specifically in protective buildings, high-performance pavements and offshore concrete structures. In this context, this paper reports on an experimental investigation aimed at assessing the effects of stimulated autogenous self-healing of UHPC on the recovery of its performance under impact loadings. Drop weight tests were performed on UHPC slabs, with a 10 kg heavy impactor dropped from the height of 1 m on the centre of the specimens. Specimens were pre-cracked by repeated impacts up to 40% of their predetermined capacity. Pre-cracked specimens were exposed to different healing conditions, water submersion, 95% +/- 5% RH, and wet/dry cycling (12/12 h) either in water or in a NaCl solution. Self-healing was evaluated through rebound height, elastic stiffness recovery, natural frequency, and laser displacement measurements. High-speed cameras and Digital Image Correlation were used to capture rebound height and crack formation. Performance was assessed at time 0, pre-damaging, 1, 2, and 4 months. After the healing period, all specimens were tested to failure. Specimens exhibited an increasing healing efficiency when moving from 95% +/- 5% RH, over wet/dry cycling, to submerged conditions. Specimens healed continuously under submerged conditions exhibited a complete closure of surface cracks (50-150 mu m) and an 80% recovery in natural frequency. Furthermore, they showed a more than 10% increase in stiffness and energy dissipation capacity after four months of healing.

Automated summary

This paper investigates the effects of stimulated autogenous self-healing on the performance recovery of UHPC under impact loadings. Experimental results show that specimens healed continuously under submerged conditions exhibit the highest healing efficiency, with complete closure of surface cracks and over 80% recovery in natural frequency. After four months of healing, there is a significant increase in stiffness and energy dissipation capacity.