Novel Method for Measuring Permeability of Concrete

0070092这项工作的目标是开发一种新的技术，用于测量低液体渗透性的异质材料，特别是包括高性能混凝土。与传统方法相比，新方法不需要高压设备，并且它在几个小时内产生结果，而不是几天或几周，此外，它最容易在低渗透率的样品上执行，这是最难以通过其他方法测量的。新方法的原理是饱和多孔体的热膨胀动力学涉及孔隙液体的流动，因此渗透率可以通过测量热循环期间的膨胀来确定。当饱和多孔材料被加热时，孔液体比固相膨胀得多，因此液体倾向于流出孔。我们的目标是设计和建造一个压力计，用于对通常用于强度测量的圆柱体进行测量。将所得渗透率值与通过常规方法获得的渗透率值进行比较。测试将在水泥、砂浆和混凝土上进行，以探索可测量的渗透率范围。将对实验进行数值分析，以探索分析计算的局限性，其中涉及一些简化假设。然而，物体的低渗透性阻止液体在膨胀时快速逸出，因此被迫在孔隙内膨胀，像弹簧一样拉伸多孔体。如果物体被加热，然后保持在恒定的温度下，初始膨胀部分是由液体引起的;在等温保持期间，液体从孔中排出，物体收缩到由固体的热膨胀系数确定的尺寸。可以计算出由液体贡献的膨胀的大小，因此将测量的膨胀与理论拟合提供了渗透率作为参数。

0070092The goal of this work is to develop a novel technique for measuring low liquid permeabilities in heterogeneous materials, particularly including high-performance concrete. In contrast to conventional methods, the new method does not require high pressure apparatus and it yields results in a few hours, rather than days or weeks moreover, it is easiest to perform on samples of low permeability, which are the most difficult to measure by other methods. The principle of the new method is that the thermal expansion kinetics of a saturated porous body involves flow of the pore liquid, so the permeability can be determined by measuring the dilatation during a thermal cycle. When a saturated porous material is heated, the pore liquid expands much more that the solid phase, so the liquid tends to flow out of the pores. Our objective is to design and build a dilatometer to perform the measurement on cylinders of the kind typically used for strength measurements. The resulting permeability values will be compared to those obtained by conventional methods. Test will be performed on cement, mortar, and concrete to explore the range of measurable permeabilities. A numerical analysis of the experiment will be performed to explore the limits of the analytical calculation, which involves some simplifying assumptions However, the low permeability of the body prevents the liquid from escaping as fast as it expands, so is forced to expand within the pores, stretching the porous body like a spring. If the body is heated and then held at a constant temperature, the initial expansion is caused in part by the liquid; during the isothermal hold, the liquid drains from the pores and the body contracts to the dimension determined by the thermal expansion coefficient of the solid. The magnitude of the dilatation contributed by the liquid can be calculated, so fitting the measured expansion to the theory provides the permeability as a parameter.