Effects of different kinds of carbon black nanoparticles on the piezoresistive and mechanical properties of cement-based composites

Carbon black nanoparticles (CBN) of different sizes, morphologies, microstructures and surface areas can be used to develop cement-based materials for strain monitoring and damage detection of concrete structures. There is a lack of systematic comparisons between mechanical and electrical properties of smart mortars fabricated with CBN of different characteristics. In this study, (4 × 4 x 7.5) cm prismatic composites containing CBN of distinct dibutyl phthalate (DBP) absorption number, conductivity and surface area were produced and subjected to direct current (DC), biphasic DC, piezoresistive and compression tests. Results show that CBN aggregates with the lowest structure (DBP of 125 cm³/100 g) and the highest resistivity provided high values of gauge factor, stress sensitivity and compressive strength, while CBN aggregates with very high structure (174 cm³/100 g) and low resistivity provided low internal capacitance and high electrical conductivity. The experimental data indicated that increases in structure and surface area improved the conductive network and reduced the internal capacitance, but decreased both compressive strength and piezoresistive response, due to reductions of variations of tunneling resistance between nanofillers. •High structured carbon blacks provided significant reductions in the capacitance of smart composites.•Increases in structure and surface area of CBN aggregates provided composites with lower resistivity.•CBN aggregates with lower structures provided the best results of sensing ability and compressive strength.•Effects of structure and surface area of CBN in contact and tunneling conduction were evaluated.