Effect of Particle Size of Si-Mn Slag on Hydraulic Mechanism and Mechanical Property in Composite Cementitious System
ZHOU Xiang1,2, ZHAO Huatang2,3, LI Liang1,2, DU Lang1,2, ZHOU Shuangfu1,2, SHAO Zhao1,2, ZHANG Xiaomin1,2
1 Chengdu Institute of Products Quality Inspection Co.,Ltd., Chengdu 610100, China 2 National Center for Building Material Quality Supervision and Inspection(Sichuan), Chengdu 610100, China 3 Sichuan Institute of Product Quality Supervision and Inspection, Chengdu 610100, China
Abstract: To achieve the high efficient utilization of Si-Mn slag, a Si-Mn slag powder was classified into three fractions by an air classifier, with D50=6.9 μm, 17.9 μm, 56.4 μm, respectively. The effect of size fraction of Si-Mn slag on hydraulic activity and physical property in composite cementitious system were investigated by isothermal calorimeter(TAM air), X-ray diffraction (XRD), mercury intrusion porosimeter(MIP), scanning electron micorscope and energy dispersive X-ray spectrometer(SEM-EDS). The test results indicated that the early hydration reaction(30 min) of free lime, aluminate and C3S phase were promoted by all size fractions of Si-Mn slag from nucleation induction. The intensity peaks of Ca(OH)2 and clinker decreased dramatically with the decrease of particle size in the late hydration. The blended cement paste with finer Si-Mn slag resulted in a decrease in the most probable pore size and total porosity than that of the one with coarser Si-Mn slag. The SEM-EDS results further demonstrated that the hardened blended cement paste containing fine Si-Mn slag powder produced a denser microstructure because more C-S (Al, Mg)-H gels hydration products with low calcium were produced. It was noted that the strength could surpass the technical index of 42.5 grade cement in GB 175 standard when the content of Si-Mn slag powder with D50=6.9 μm and 17.9 μm was reached up to 30%. Thus, these fractions were strongly recommended to serve as mineral admixtures in blended cement production or concrete making.