Electrically cured ultra-high performance concrete (UHPC) embedded with carbon nanotubes for field casting and crack sensing

• Published in: Materials & design 2020-11, Vol.196, p.109127, Article 109127
• Main Authors: Jung, Myungjun, Park, Jiseul, Hong, Sung-gul, Moon, Juhyuk
• Format: Article
• Language: English
• Subjects: Carbon nanotubes (CNTs); Electrical curing; Mechanical properties; Self-sensing materials; Ultra-high performance concrete (UHPC)
• ISSN: 0264-1275; 1873-4197
• DOI: 10.1016/j.matdes.2020.109127

The effects of incorporating carbon nanotubes (CNTs) into ultra-high performance concrete (UHPC), thereby forming UHPC/CNT composites, were investigated in terms of electrical curing efficiency, mechanical properties, and crack sensing capability. The addition of CNTs significantly decreased the electrical resistivity of the UHPC, allowing effective electrical curing at low voltage; improved mechanical properties through bridging, pore filling, and calcium-silicate-hydrate (C-S-H) stiffening effects; and favorably influenced the deflection hardening and multiple cracking behavior under flexural stress. Furthermore, the developed UHPC/CNT composites subjected to compressive or flexural stress showed significant crack sensing capability due to the obtained low electrical resistivity. A dramatic fractional change in the resistivity (FCR) of the UHPC/CNT composites can represent the failure under compression or first cracking under flexure. Therefore, it was experimentally verified that the UHPC/CNT composites can extend the applications of UHPC materials especially for on-site casting and structural crack sensors for UHPC-based structures. [Display omitted] •Well-dispersed CNTs substantially decreased the electrical resistivity of the UHPC by forming connections with steel fibers.•The electrical characteristic of the UHPC/CNT allows effective electrical curing using significantly low voltages•Electrically cured UHPC/CNT shows better performance due to the electric field formed and activated ionic polarization•Crack sensing capability (i.e., not stress sensing capability) was confirmed in the proposed UHPC/CNT composite.