Mix Procedure of Ultra-High Performance Concrete Containing Nano-Silica; Advantages And Challenges To Achieve Required Characteristics

The paper describes the mix method and the results of the influence of nanoparticles of nano silica (NS) (d ≈ 65 nm) on the Ultra-High performance Concrete (UHPC) matrix properties. Five different contents of NS particles were applied: 0, 0.5, 1, 1.5, and 2 wt.% by weight of cement. The studies regarding different physical and mechanical parameters of cementitious composite matrix specimens such as water absorption, porosity, compressive strength and flexural strength. Structural properties have been carried out and the results of these studies are presented and discussed. It was shown that the nanoparticles in the amounts of 1-2 wt.% can influence the cement hydration process and thereby enhance the compressive strength of cementitious composite. The higher enhancement was obtained during the first three days of hardening due to so called filling effect. In the following stage of hydration, the strengthening effect diminished. This phenomenon was convergent with the XRD analysis, which proved that the nanoparticles react with the cement paste components.