不同养护制度下掺铁尾矿粉超高性能混凝土力学性能

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

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.

Iron tail mineral powder(ITMP)was used to replace quartz powder(QP)to produce ultra-high performance concrete(UHPC).The mechanical properties of the prepared UHPC under different curing conditions were experimentally studied.It was found that the fluidity of the prepared UHPC slightly decreased with the increasing replacement ratios of QP by ITMP,while the mechanical properties kept almost unchanged.Compared to the standard curing(SC),the water curing(WC)and autoclaved curing(AC)can significantly improve the compressive and flexural strengths,and the ratio of flexural-to-compressive strength of the target ITMP-UHPC.Based on test results obtained at the micro scale,the replacement of QP by ITMP was not detrimental to the microhardness and pore structure of the cement matrix of UHPC.Under WC and AC conditions,the hydration of cement was promoted with the generation of products with lower Ca/Si ratios compared to those under SC;the microhardness and pore structure of the cement matrix were also improved greatly.The autoclaved curing may have also activated the pozzolanic activity of silica fume,QP,as well as ITMP,which led to the further crystallization of C-S-H(with a structure similar to that of Tobermorite)by secondary hydration of cement.It was suggested that it should be feasible to use ITMP to prepare UHPC with ensured mechanical properties and also good environmental and economic benefits.