Dual Self-Healing Mechanisms with Microcapsules and Shape Memory Alloys in Reinforced Concrete

Abstract

This paper presents an evaluation of dual self-healing mechanisms in concrete, with a focus on the application of microcapsules and shape memory alloy (SMA). To achieve this objective, the study evaluated the self-healing effectiveness of calcium nitrate microcapsules in concrete beams reinforced with steel and SMA. The undamaged stiffness, damaged stiffness, peak strengths, and deformations were measured and compared with postcuring time values. Further, crack monitoring coupled with an energy-dispersive X-ray (EDX) spectroscopy analysis was used to evaluate crack healing over time and to characterize the healing components in the cracked areas. Experimental results suggest that microcapsules caused a direct effect on decreasing the flexural strength of concrete beams, attributing the results to the presence of high air content when the microcapsules are used. Although microcapsules tended to lower the flexural strength of the beams, the stiffness recovery values were higher for those specimens prepared with microcapsules. An image analysis conducted after the water curing period revealed that specimens with microcapsules showed the best crack healing efficiency, regardless of the use of steel or SMA. In the use of heat activation, not only was crack healing efficiency observed with SMA, but also a noticeable difference was found in SMA samples, with or without microcapsules.