Effect of Moisture on Piezoresistivity of Carbon Fiber-Reinforced Cement Paste

Abstract

Piezoresistivity, as exhibited by carbon fiber-reinforced cementbased material, allows a structural material to sense its strain or stress through electrical resistance measurement. This paper addresses the worst scenario associated with the effect of moisture on the piezoresistivity of carbon fiber-reinforced cement paste. This scenario is associated with both water saturation and a fiber content below the percolation threshold. For this scenario relative to the condition after drying at room temperature, the gauge factor (fractional change in resistance per unit strain) is decreased by at least 12% and the variability of the gauge factor with the strain amplitude and with the strain history is increased. These negative effects are attributed to the water at the fiber-matrix interface. The water interferes with the electronic conduction across the interface. Nevertheless, the piezoresistivity remains strong, the signal-to-noise ratio of the resistance remains high, and the relationship between resistivity and strain remains quite linear.

Piezoresistivity and AC Impedance Spectroscopy of Cement-Based Sensors: Basic Concepts, Interpretation, and Perspective

“…Electrical conduction, on the other hand, is dominated by electronic conduction with the addition of conductive admixtures at a volume percentage near the percolation threshold (see Section 2.5 for more information), significantly lowering the humidity dependence [ 67 ]. Although the humidity reliance is not entirely removed [ 58 ], the influence of humidity on the sensing performance is minimal [ 77 ].…”

“…Piezoresistivity in a cement-based matrix containing short carbon fibres is caused by a minor slippage of the fibre–matrix interface, as illustrated in Figure 6 [ 58 , 116 ], and an accompanying increase in the interface resistivity [ 118 , 119 ]. There are other causes of piezoresistivity in cement-based materials containing conductive fillers, such as the change in intrinsic resistance of the conductive admixtures, the change in contact resistance between the functional additives, the change in tunnelling distance between the conductive admixtures, and the change in capacitance distance of the conductive fillers [ 57 ].…”

“…The cause of piezoresistivity in cement-based materials is based on one or more of these factors: the slippage of the fibre–matrix interface [ 57 , 58 , 59 , 60 , 61 , 62 ], the change in the intrinsic resistance of the conductive admixtures [ 57 , 59 , 63 , 64 ], the change in the contact resistance between the functional additives [ 57 , 65 ], the change in the tunnelling distance between the conductive admixtures [ 57 ], and the change in the capacitance distance of the conductive fillers [ 57 , 66 ].…”

Experimental Study of Factors on the Conductive Properties of Carbon Fiber Reinforced Concrete

“…Compared with ordinary concrete, the resistance can be reduced from 10 9 Ω•cm to the limits of 10 2 Ω•cm. As a result, based on characteristics of structural material and conductive properties [3,4,5], the conductive concrete has greater use that ordinary concrete does not.…”