不同养护制度下掺铁尾矿粉超高性能混凝土力学性能

采用铁尾矿粉取代石英粉配制超高性能混凝土(ultra-high performance concrete, UHPC),研究不同养护制度下掺铁尾矿粉UHPC力学性能.结果表明:随铁尾矿粉取代率增加, UHPC流动度略有下降,力学性能基本不变;与标准养护相比,恒温水养和蒸压养护下掺铁尾矿粉UHPC抗压、抗折强度及折压比显著提升.结合微观试验结果发现,铁尾矿粉取代石英粉对水泥石显微硬度及孔结构无不利影响.恒温水养和蒸压养护下掺铁尾矿粉UHPC的水泥水化更充分,水化产物Ca/Si比值下降,水泥石显微硬度增大、孔结构改善;蒸压养护还可能显著激发硅灰、石英粉和铁尾矿粉的火山灰活性,参与二次水化,生成结构更致密的C-S-H(结构类Tobermorite晶体).采用铁尾矿粉取代石英粉制备力学性能达标的UHPC是可行的,此举将同时产生良好的环保和经济效益.

Mechanical properties of UHPC prepared with iron tail mineral powder cured under different conditions

Iron tail mineral powder (ITMP) was employed to replace the quartz powder (QP) to produce ultra-high performance concrete (UHPC). The mechanical properties of the prepared UHPC cured under different conditions were experimentally studied. It was found that the fluidity of the prepared UHPC slightly decreased as more QP was replaced by ITMP, while the mechanical properties almost unchanged. Mechanical properties of UHPC prepared with ITMP were found significantly improved under the water curing (WC) and autoclaved curing (AC) conditions, compared to those under the standard curing (SC) conditions. Based on results obtained from the XRD, SEM, microhardness, and pore structure tests, it was found that ITMP mainly induced filling effects as micro filler in the prepared UHPC. It was also found that under WC and AC conditions, cement became more fully hydrated compared to that cured under the SC condition. WC and AC can improve the polymerization and reduce the alkalinity of the produced C-S-H; they can also enhance the microhardness and improve the pore structure of the cement matrix. When the prepared UHPC was cured under the AC condition, Ca(OH)2 was almost completely consumed and denser tobermorite was generated. It was suggested that it should be feasible to use ITMP to prepare UHPC with good mechanical properties and also good environmental and economic benefits at the same time.