Self-Sensing Mortars: Effect of Moisture and Nanocarbon Black Content

The mutual effects of water content and carbon black nanoparticle (CBN) concentration on the electrical resistivity and self-sensing properties of mortars are reported in this paper. Previous works have focused on moisture effects in CBN-based composites whose conductivity mainly came from direct contact between nanofillers. This study found very distinct behaviors when the CBN concentration was within the percolation zone. Mortars containing different moisture and CBN contents were subjected to direct current (DC) measurements, biphasic DC, and piezoresistivity tests. Effects of water content on the intrinsic capacitance of CBN-based composites were reported. A deep investigation within the percolation zone allowed the design of a promising CBN-based composite whose resistivity and sensing properties are minimally dependent on the water content, because the effects on ionic conduction due to the elimination of pore water were compensated by the effects on contacting conduction due to the elimination of water films on CBN surface. Keywords: capacitive behavior; carbon black nanoparticles; electrical resistivity; piezoresistivity; smart cement-based composites; structural health monitoring; water content.