Positive effects of novel nano-zirconia on flexural and compressive strength of Portland cement paste

[Display omitted] •The object of research is to improve concrete mechanical properties.•Nano zirconia has been prepared via simple and low-cost hydrothermal method.•Nano zirconia has been introduced to concrete at different dosage.•1.5%wt of nano zirconia has been obtained as the optimum weight percent.•In higher dosage than 1.5%wt the performance of concrete slightly decreases. The study was conducted to investigate the effects of nano-zirconia on the compressive and flexural strengths of concrete. For this purpose, the hydrothermal method was applied for the preparation of nano zirconia. Crystallinity, purity and structural properties of the prepared product were determined via X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and Fourier-transform infrared spectroscopy (FTIR) analysis. Zirconia nanoparticles were applied as nano-filler with partial replacement of ordinary Portland cement (OPC) by 0.5, 1.0, 1.5, 2.0, 3.0 and 4.0 wt%. The strength of OPC was determined via flexural and compressive strength tests on 3, 7 and 28 days. The results cleared that 1.5%wt have the highest improvement on the concrete. Overall, flexural and compressive strengths of OPC paste were increased first (0.5, 1 and 1.5%) then decreased (2, 3 and 4%) in 3, 7 and 28 curing days. Flexural strength was improved with 19.9% after 3 days, 17% after 7 days and 14.6% after 28 days. Compressive strength was improved with 14.9, 9.8 and 11.4% after 3, 7 and 28 days respectively.