An investigation on mechanical and electrical properties and microstructure of Ultra-High Performance Concrete Containing Silica Fume and PVA Fiber

Ultra-high performance concrete (UHPC) is a new type of composite materials that can develop a compressive strength up to 200  MPa and high tensile strength around 10 MPa, given the low water-to-binder ratio (W/B). The fracture energy of UHPC can vary from 8560 to 40,000 J/m2, which is approximately 220 times greater than that of conventional mortar. Due to its superior properties, Ultra-high performance concrete has received great attention among researchers recently. Very high compressive strength leads to a significant weight loss of the structure and makes it possible to build slender structural elements. In this paper, the ultra-high performance fiber reinforced concrete specimens exposed to two different curing regimes, a 23°C limewater tank, and a 70°C hot-water tank. Then, the compressive and flexural strength and the electrical behavior of specimens were evaluated. Mechanical strength at the age of 28 days and six months were measured, in order to in conjunction with durability-related properties offer an overall view of UHPFRC characteristics. Results showed that the PVA fiber affected the mechanical strengths by preventing the propagation of cracks and by increasing the total porosity of the matrix. Moreover, its influence on resistivity was highly dependent on the concentration of silica fume particles.