Behavior of Piezoresistive Cement Based Materials

The piezoresistive behavior of cement based composites reinforced with conductive filler was investigated under uni-axial compression. The conductive filler contents used in this study were 3% and 6% (by weight of dry mix). The average 28 days compressive strength was 14.75 MPa and 11.00 MPa for the 3% and 6% composites respectively where the water-to-cement ratio was 1. Under compression, the specific electrical resistivity of the composites changed with applied stress, proving the piezoresistive nature of the composite. The specific electrical resistivity initially decreased with increasing stress but after a certain stress value (threshold change of resistivity), it increased with stress increase up to failure. The piezoresistivity parameters such as piezoresistivity coefficients and gage factors were quantified and found to be dependant on the filler content. Increasing the filler content to 6% increased the piezoresistivity coefficients and gage factor parameters. A constitutive model relating the change in the specific electrical resistivity to the applied compressive stress was used to predict the piezoresistive behavior of the composites. The model predicted the piezoresistive behavior of the composites.