Terahertz (THz) Wave Imaging in Civil Engineering to Assess Self-Healing of Fiber-Reinforced Cementitious Composites (FRCC)

Although numerous studies have proven the effectiveness of self-healing technologies in concrete, its practical application is limited to only few trials. One of the reasons lies in the lack of self-healing in-situ non-destructive evaluation methods as opposed to invasive and extensive laboratory testing. In this study, a novel Terahertz (THz) wave imaging technique is proposed as a simple, non-destructive, and non-contact measurement methodology to quantitatively evaluate the self-healing effectiveness of cementitious materials. Experiments were conducted in fiber-reinforced cementitious composites (FRCC), which confirmed self-healing performance based on a combination of stimulated autogenous and autonomous healing by using supplementary cementitious materials (FRCC), and PVA fibers; the self-healing index was also calculated by using novel THz wave measurement and compared with existing evaluation methods. Simultaneously, sorptivity test and microstructural characterization on damaged and healed specimens were conducted as the conventional methods. As a result, the proposed THz imaging successfully quantified the self-healing performance on cementitious samples. Also, a correlation between the recovery rate (cracked/healed) measured by sorptivity test and THz wave imaging was defined.