基于X-CT的非饱和水泥基材料水分传输与渗透系数计算

利用X射线计算机断层扫描(X-CT)联合Cs离子增强技术连续监测水分在非饱和水泥基材料中的动态传输过程,建立水分传输距离与时间的关系,获得水分传输的毛细吸水系数,在此基础上提出了计算水泥基材料渗透系数的理论模型。系统研究了水灰比、粉煤灰掺量、矿渣掺量和砂体积掺量对水泥基材料毛细吸水系数和渗透系数的影响,结果表明:当水灰比从0.35增大到0.55时,硬化水泥浆体的毛细吸水系数从2.07×10^-4 m/s^1/2增大到3.22×10^-4 m/s^1/2,而固有渗透系数增大1个数量级;粉煤灰的掺入能有效降低浆体的水分传输性能,且粉煤灰的最佳掺量为30%(质量分数),当矿渣掺量为30%(质量分数)时,硬化浆体的固有渗透系数比掺同等质量粉煤灰的高1个数量级;当砂体积掺量从0%增加到40%时,砂浆的毛细吸水系数和固有渗透系数均下降,当砂体积掺量大于42.4%时,砂浆的界面过渡区(ITZ)连通,砂浆的毛细吸水系数增大。

Water Transport and Permeability Coefficient Calculation for Unsaturated Cement-Based Materials Based on X-CT

The technique of X-CT combined with Cs ion enhancing was used to detect the movement of water transport in unsaturated cement-based materials. From that, the relationship between the distance of water uptake and exposed time was established, and the capillary coefficient was obtained. What’s more, a theoretical model for calculating the intrinsic permeability coefficient based on capillary coefficient and pore structure was provided. Effects of water to cement ratio, fly ash content, ground granulated blast furnace slag content and volume fraction of sand on the capillary coefficient and intrinsic permeability coefficient were investigated systematically. The results show that the capillary coefficient increases from 2.07×10^-4 m/s^1/2 to 3.22×10^-4 m/s^1/2 with the water to cement ratio increasing from 0.35 to 0.55, and the intrinsic permeability coefficient increases by one order of magnitude. The addition of fly ash effectively decreases the property of water transport in cement paste, and the ideal content is 30% (mass fraction). The intrinsic permeability coefficient of cement paste with 30% (mass fraction) ground granulated blast furnace slag is one order of magnitude higher than that with 30% (mass fraction) fly ash. For water transport in mortars, both of the capillary coefficient and intrinsic permeability coefficient decrease with the sand volume fraction increasing from 0% to 40%. It also concludes that the ITZ of mortar connect completely when the volume fraction of sand comes up to 42.4%.