Synergistic effects of single-walled carbon nanotube and carbon fiber on performance of conductive mortar

Single-walled carbon nanotube (SWCNT) and carbon fiber (CF) have been demonstrated to be conducive to an improved electrical conductivity of cement-based composites. However, there have been few studies on the possible hybrid use of SWCNT and CF to further promote the electrical conductivity and perhaps also other performance attributes. In this study, a trial to utilise both SWCNT and CF to produce conductive mortar was launched. A series of 20 mortar mixes featuring varying water-to-cement ratios, SWCNT contents and CF contents were tested to reveal their combined effects on fresh workability, mechanical strength, dimensional stability, electrical conductivity and microstructure. Test results exhibited that the co-addition of SWCNT and CF derived adverse effect on workability, but remarkable beneficial effects on strength, dimensional stability and electrical conductivity, and more interestingly, some combinations of SWCNT and CF showed synergistic effects. From the microscopic morphology, the agglomeration of SWCNT is an important causation for the decline in strength and dimensional stability of mortar. Finally, some mix proportions suitable for conductive mortars are proposed. •Adding SWCNT and/or CF improved strength, dimensional stability and electrical conductivity.•Some combinations of SWCNT and CF show synergistic effects.•SWCNT agglomeration is a vital reason for the decline in strength and dimensional stability.