Cement-based sensors with carbon fibers and carbon nanotubes for piezoresistive sensing

Electrically conductive cementitious composites carrying carbon fibers and carbon nanotubes were developed and their ability to sense an applied compressive load through a measureable change in resistivity was investigated. Two types of cement-based sensors, one with carbon fibers alone and the other carrying a hybrid of both fibers and nanotubes, were considered. Direct comparisons were also made with traditional strain gauges mounted on the sensor specimens. Sensing experiments indicate that under cyclic loading, the changes in resistivity mimic both the changes in the applied load and the measured material strain with high fidelity for both sensor types. The response, however, is nonlinear and rate dependent. At an arbitrary loading rate, the hybrid sensor, containing a combination carbon fibers and nanotubes, produced the best results with better repeatability.