养护条件对水泥基材料孔隙结构的影响

Effect of Curing Conditions on Pore Structure of Cement Based Materials

通过压汞法测量孔隙分布、孔隙率和体积、特征孔隙尺寸、孔隙比表面积和曲折度,研究了养护条件对密封养护净浆和砂浆试件的孔隙结构的影响。结果表明:密封养护对水泥基材料的比表面作用较小,但是能显著提高其孔隙率;密封养护加剧自干燥作用,导致水泥基材料在10～100nm和100～1000nm区间出现明显的孔隙分布峰,且峰强和最可几尺寸均随着水灰比的增加而增加;密封养护导致水泥基材料的临界孔隙尺寸减小但是对平均孔径均影响较小;净浆和砂浆的退汞残余和曲折度均随着水灰比的增加而降低,且曲折度与孔隙率的关系大致符合指数规律。密封养护条件下自干燥导致微结构变化的模型表明:水泥基材料在低含水量条件下水化不充分,孔隙压力大,容易出现连通的大毛细孔和微裂纹;水灰比越大,该现象越明显。

The effect of self-desiccation on the pore structure of cement pastes and mortars was investigated by mercury intrusion porosimetovy （MIP）. The porosity, pore size distribution （PSD）, characteristic pore size, specific surface area （SSA） and tortuosity of the samples wove determined. The results show that there are two PSD peaks in the pore size ranges of 10-100nm and 100-1 000nm for all the sealed curing samples. The intensity and pore size increased with increasing the watov-cement ratio. The self-desiccation, which was strengthened by sealed curing, decreased the critical pore size, hut had a limited influence on the mean pore size. The self-desiccation had a slight effect on the SSA, but affected the porosity. The mercury entrapment and tortuosity both decreased with increasing the water-cement ratio, and the relationship between the tortuosity and porosity followed roughly the power law. A descrip-tive model for pore structure altered by self-desiccation under sealed curing condition was proposed. It was indicated that a lower hydration extent by the limited water supply and high capillary tension contributed to form the pore path percolation, especially at a greater w/c ratio.