水泥-硅微粉复合胶凝材料颗粒级配对其力学性能和孔结构的影响

Effect of the Grain Size Distribution on Mechanical Property and Pore Structure of Cement-Silicon Powder Composite Binder

利用四种不同比表面积的硅微粉(958 m^(2)/kg、1 189 m^(2)/kg、1 385 m^(2)/kg和3 226 m^(2)/kg)调配水泥基复合胶凝材料的级配,基于Fuller曲线拟合了不同级配条件下的特征指数,研究水泥-硅微粉复合胶凝材料在不同特征指数条件下(0.407 4~0.467 8)的力学性能和孔结构的变化规律.通过试验分别得到胶砂试件在7 d和28 d时的抗压强度和抗折强度的变化规律,利用吸水动力学法测得复合胶凝材料硬化浆体孔隙结构的变化规律,结合扫描电镜(Scanning Electron Microscopy, SEM)对复合胶凝材料硬化浆体的微观结构进行分析.硅微粉掺量为15%且复合胶凝材料的粒径控制在50μm以内时,胶砂试件的强度和硬化浆体的平均孔径随着特征指数的增加呈先升高后降低的趋势,7 d和28 d时胶砂强度的最大值所对应的特征指数分别是0.413 6和0.433 4;7 d和28 d时,硅微粉与水泥颗粒之间分别存在一个最佳颗粒级配,使复合胶凝材料硬化浆体的微观结构更加致密,从而提高水泥基复合材料的力学性能.

Four kinds of silicon powder of different specific areas(958 m^(2)/kg、1 189 m^(2)/kg、1 385 m^(2)/kg and 3 226 m^(2)/kg)are used for controlling the gradation of composite cementitious materials. The characteristic indexes in different conditions are fitted based on the Fuller curve, which use for studying the variation of mechanical property and pore structure of the cement-silicon powder composite cementitious materials in different characteristic indexes(0.407 4~0.467 8). The variety of compressive strength and flexural strength is measured by mortar test on the 7 th and 28 th days. The variety of pore structure of complex binder paste is measured by water-absorbing dynamics. Microstructures of complex binder paste were reported by the scanning electron microscope(SEM). The results show that, when the silicon powder is mixed with 15% and the particle size of the composite cementitious materials is controlled to be less than 50μm, the mechanical property of mortar and average pore size of hardened paste increase first and then decrease with the increase of the characteristic index. The characteristic indexes corresponding to the maximum strength of mortar are 0.413 6 and 0.433 4 on the 7 th and 28 th days. On the 7 th day and 28 th day, there is an optimal gradation between silica powder and cement, which makes the microstructure of hardened paste of composite binder more compact, thus improving the mechanical properties of cement composites.