Smart cement composites for durable and intelligent infrastructure

The self-healing and self-sensing performances of Engineered Cementitious Composite (ECC) mixtures developed recently at Heriot-Watt University are presented. In the first series of experiments, fifteen dog-bone shaped ECC samples were preloaded to known strains and then left to heal outdoors under a natural environment. Ultrasonic pulse velocity measurements were then undertaken periodically to determine the rate and extent of healing in these samples. It was found that the samples were able to heal micro-cracks and show a recovery in UPV after two loading events over a six month outdoor exposure. In another series of experiments, the effectiveness of incorporating milled carbon (MC) fibers into an ECC mix, with the aim of enhancing the self-sensing functionality of ECC, is demonstrated for the first time. The MC-ECC mix exhibited equivalent tensile response compared to the control ECC mix and displayed a strong relationship between tensile strain and the fractional change in resistivity. The inclusion of MC fibers at 0.75% by volume was found to exhibit high sensitivity to micro-cracks formation, with gauge factor two orders of magnitude larger than that of an ordinary strain gauge, albeit less than that of the control mix. It is envisaged that the use of ECC can create an intelligent infrastructure able to sense and repair damage and monitor the recovery extent.