Carbon-fiber-reinforced concrete smart structures capable of nondestructive flaw detection

Electrically conducting concrete, as provided by the addition of short carbon fibers (0.2 - 0.4 vol.%) to concrete, can function as a smart structure material that allows non-destructive electrical probing for the monitoring of flaws. The electrical signal is related to an increase in the concrete's volume resistivity during crack generation or propagation and a decrease in the resistivity during crack closure. The linearity between the volume resistivity change and the compressive stress was good for the mortar containing carbon fibers together with methylcellulose as a dispersant; when the compressive stress was increased in the first cycle up to the fracture stress, the volume resistivity increased by 1040%. In contrast, mortars without carbon fibers showed no variation of the resistivity upon compression up to fracture.