الفهرس | Only 14 pages are availabe for public view |
Abstract This study aimed to utilize some laboratory prepared nano oxides namely; nano silica (NS), nano alumina (NA), nano hematite (NF) and nano zinc oxide (NZ) as active additions for improving the microstructure, mechanical properties and thermal resistance of hardened ordinary Portland cement (OPC) pastes. Nano silica was synthesized from rice husk ash via extraction method, while, nano alumina, nano hematite, and nano zinc oxide were synthesized from AlCl3, FeCl3.6H2O and zinc acetate; respectively via the sol-gel method in presence of CTAB as a cationic surfactant. The average particle sizes of synthesized NS, NA, NF and NZ were 30, 40, 20 and 70 nm; respectively. NS, NA, and NF were added to OPC with ratios of 0.5, 1, 2 and 3 by mass% of OPC. While, NZ was added to OPC with ratios of 0.05, 0.1 and 0.2 by mass% of OPC. The physicochemical and mechanical characteristics of the hardened pastes were investigated after 1, 3, 7, 14, 28 and 90 days of curing under tap water hydration. For thermal resistance test, the specimens were hydrated for 28 days under tap water and fired at 300, 600 and 800oC for 3 h. The compressive strength test was performed for all fired specimens at each firing temperature. The results indicated that the optimum addition of NS, NA, NF, and NZ was 1, 0.5, 2 and 0.05%; respectively. XRD, TG/DTG, and SEM results indicated that illcrystalline and nearly amorphous nature of the formed hydrates in these hardened composites. Keywords Nano silica, Nano alumina, Nano hematite, Nano ZnO, Thermal resistance, Compressive strength, Pozzolanic activity. |