Diffusion potentials in non-saturated, porous mineral materials – error and information source

在混凝土或土壤等多孔材料中，由于环境暴露，孔隙溶液的化学成分可能会表现出空间差异。因此，存在扩散电势，并且可以容易地达到几十毫伏或超过100 mV。一个主要的影响已被确定在梯度的pH值，由于较高的流动性的阴离子相比，伴随cations.Diffusion在多孔矿物材料的电位有显着的影响，在研究和实践中的测量。因此，它可能会导致相当大的误解的结果，并最终影响评估。现有技术允许预测饱和多孔矿物材料中的扩散势。我们将继续进一步研究考虑在非饱和材料的选择渗透行为的扩散势。本项目的总体目标是显着提高目前的理解多孔矿物材料，特别是在水泥基材料和桑迪中的扩散势。其目的是提高基于材料特性和暴露条件的扩散电位预测的准确性。主要关注的情况是氯化物暴露引起的条件以及碳酸化或沥滤引起的pH值差异。到目前为止，考虑的是饱和材料。在实践中，如果结构物不浸没在水中，则混凝土通常是非饱和的。因此，该条件状态比饱和状态具有更高的实际相关性。因此，我们的目标是开发一个工具来预测扩散势的情况下，非饱和concrete.The结合的实验测量（TUM）与数值模拟（ETHZ）的基础上开发的扩散势的预测工具。进行扩散电位的测量。将通过压汞法、核磁共振弛豫法、电化学阻抗谱法对研究材料进行表征（孔隙率、含水量）。离子浓度梯度的测定将通过激光烧蚀电感耦合等离子体质谱法（LA-ICP-MS）等方法进行。数值模拟是基于Poisson-Nernst-Planck方程的。在扩散势是误差源的情况下，能够预测扩散势对于应用适当的校正至关重要。此外，对材料的选择性渗透特性及其对扩散电势的影响的更好理解也可以允许使用扩散电势的测量作为获得关于所研究的材料的信息的手段。一些工程任务和当前的研究将受益于发展的科学基础，预测扩散潜力。这包括电位测量、腐蚀监测和阴极保护。

In porous materials such as concretes or soils, the pore solution is likely to exhibit spatial differences in chemical composition in cause of environmental exposure. Thus, diffusion potentials are present and may easily reach several tens of millivolts or exceed 100 mV. A major influence has been identified in gradients of pH due to the higher mobility of anions in comparison to the accompanying cations.Diffusion potentials in porous mineral materials have a significant effect on measurements in research and practice. Consequently, it may lead to considerable misinterpretation of the results and eventually affects the assessment. The present state of the art allows prediction of diffusion potentials in saturated, porous mineral materials. We will continue with further study considering diffusion potentials in non-saturated materials with perm-selective behavior.The overall objective of this project is to significantly improve the current understanding of diffusion potentials in porous mineral materials, particularly in cement-based materials and in sandy soils. The aim is to enhance the accuracy of predictions of diffusion potentials based on material properties and exposure conditions. The situations of main interest are conditions arising from chloride exposure as well as pH differences due to carbonation or leaching. So far, saturated materials were considered. In practice, concrete is normally non-saturated, if structures are not submerged in water. Therefore, this condition state is of higher practical relevance than the saturated state. Consequently, the aim is the development of a tool to predict diffusion potentials in case of non-saturated concrete.The combination of experimental measurements (TUM) with numerical simulations (ETHZ) is the basis for developing the predictive tool for diffusion potentials. Measurement of diffusion potentials is carried out. Characterization (porosity, moisture content) of materials under study will be done by mercury intrusion porosimetry, nuclear magnetic resonance relaxometry, electrochemical impedance spectroscopy. Determination of ion concentration gradients will be done by methods such as laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Numerical simulations are based on Poisson-Nernst-Planck equations.Being able to predict diffusion potentials is crucial to apply adequate corrections in case of diffusion potential is an error source. Furthermore, an improved understanding of the perm-selective properties of the material and their influence on diffusion potentials may also allow using measurements of diffusion potentials as a means to obtain information about the material under study. Several engineering tasks and current research will benefit from developing the scientific basis for the prediction of diffusion potentials. This includes potentiometric measurements, corrosion monitoring, and cathodic protection.