Effect of mix proportion and processing method on the mechanical and electrical properties of cementitious composites with nano/fiber fillers

This paper studies the influence of mix proportion and processing method on the mechanical and electrical properties of nano/fiber fillers filled cementitious composites. Cementitious composites with different contents of filler, contents of superplasticizer (SP), ultrasonic energy or mixing speeds are fabricated. Experimental results indicate that the optimal content of nano-silica (NS), carbon nanotube (CNT) and carbon fiber (CF) is 0.1%, 0.1% and 1% by weight of cement, respectively, when the water/cement ratio (w/c) of composites is 0.2 and the SP content is 0.75 wt%. Compared with composites with 0.1 wt% NS/0.1 wt% CNTs, cementitious composites with 1 wt% CFs have the maximum compressive strength of 152.69 MPa and the maximum conductivity of 0.1258 s m−1. When the contents of NS, CNTs, CFs remain constant, the optimal content of superplasticizer is 1.25%, 0.75% and 0.5% for each type of composites, respectively. Additionally, the optimal ultrasonic energy for nano-fillers (NS and CNTs) is 1000 kJ l−1 while that for micro-filler (CFs) is 400 kJ l−1. The optimal mixing speed for NS, CNTs and CFs is 500 r min−1. All experiments prove that the change of conductivity is basically consistent with that of compressive strength.