Properties and modification mechanisms of nano-zirconia filled reactive powder concrete

The mechanical and electrical properties of reactive powder concrete (RPC) with nano-ZrO₂ (NZ) are investigated in this research. The reinforcing mechanisms of NZ to RPC are studied through thermogravimetry (TG) analysis, scanning electron microscope (SEM) observation and X-ray powder diffraction (XRD) analysis. Research results indicate that the NZ has obvious modifying effect to RPC. The flexural, compressive and splitting strengths of RPC with NZ at curing age of 28 days achieve increases of 36.6%/4.19 MPa, 16.3%/16.18 MPa and 34.0%/1.08 MPa, respectively, compared to plain RPC. The addition of NZ makes a 20% decrease in the electrical conductivity of RPC. The NZ does not accelerate the hydration process of RPC. However, the microstructures of NZ filled RPC are denser than that of plain RPC. This leads to the reduction of the growth space of calcium hydroxide (CH) crystals, thus the size of CH crystals is reduced. Furthermore, NZ can reduce CH crystal orientation to improve the microstructures of the composites.