Novel Method for Measuring Permeability of Concrete

[00:70092]这项工作的目标是开发一种测量非均质材料（特别是高性能混凝土）低液体渗透性的新技术。与传统方法相比，新方法不需要高压仪器，在几小时内产生结果，而不是几天或几周，而且最容易在低渗透率样品上执行，这是其他方法最难测量的。新方法的原理是饱和多孔体的热膨胀动力学涉及孔液的流动，因此渗透率可以通过测量热循环过程中的膨胀来确定。当饱和多孔材料受热时，孔隙液体比固相膨胀得更大，因此液体倾向于从孔隙中流出。我们的目标是设计和制造一个膨胀计，用于测量通常用于强度测量的圆柱体。将得到的渗透率值与常规方法得到的渗透率值进行比较。测试将在水泥、砂浆和混凝土上进行，以探索可测量渗透率的范围。将对实验进行数值分析，以探索解析计算的局限性，其中涉及一些简化的假设。然而，体的低渗透性阻止液体像膨胀一样快速逃逸，因此被迫在孔隙内膨胀，将多孔体拉伸得像弹簧一样。如果物体被加热，然后保持在一个恒定的温度下，最初的膨胀部分是由液体引起的；在等温保温期间，液体从孔中流出，体收缩到由固体的热膨胀系数决定的尺寸。可以计算出液体对膨胀的贡献大小，因此将测量到的膨胀拟合到理论中可以提供渗透率作为参数。

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.