Effects of CNT concentration level and water/cement ratio on the piezoresistivity of CNT/cement composites

Carbon nanotube (CNT)/cement composites with different concentration levels of multi-walled CNT (MWNT) and water/cement ratios are fabricated. By comparing the responses of electrical resistance of these CNT/cement composites to compressive stress, the effects of MWNT concentration level and water/cement ratio on the piezoresistive sensitivity of composites are investigated. Experimental results indicate that the piezoresistive sensitivities of CNT/cement composites with 0.05, 0.1, and 1 wt% of MWNT first increase and then decrease with the increase of CNT concentration levels. Water/cement ratio is another factor that affects the composite properties, the electrical resistance of CNT/cement composite with 0.6 water/cement ratio is more sensitive to compressive stress than that of composite with 0.45 water/cement ratio. The piezoresistive sensitivity is heavily dependent on the conductive network in the composites, which in turn is influenced by the CNT concentration level and water/cement ratio.