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

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.