EAGER/Collaborative Research: New Concept of Sorption Hysteresis and Disjoining Pressure in Concrete and Other Adsorbent Microporous Solids

EARLY概念探索性研究资助（EAGER）项目的目的是阐明微孔中受阻吸附层的吸附滞后的原因，这在60多年来一直无法解释。两种机制进行了研究。一种是在非均匀孔隙的填充或排空过程中，由于孔隙厚度通过单层厚度的整数倍的失配分离压力的非唯一性，导致了一系列的快速通过不稳定性。第二个由分子聚结，或偏析，在部分填充层，无论是通过spinodal分解（线性不稳定性的均匀填充）或通过成核缺陷或孔隙开口。在宏观尺度上，这两种机制都导致了许多平行孔隙的非均匀填充或排空，以及热力学计算的分离压力的巨大变化。这些变化是干燥徐变和收缩的任何物理理论的基本部分。另一个目标是从吸附试验中确定孔径分布和内表面积，第三个目标是预测通过微孔固体的流体输送。微孔固体中的吸附滞后控制微尺度应力，微尺度应力支配微孔中和周围的蠕变和非弹性变形以及吸附过程中的能量耗散。吸附循环所消耗的能量有助于材料损坏。这些现象是预测各种混凝土结构的损坏和蠕变，甲烷从煤层中释放，岩石的气体封存能力，页岩气体释放等的根本利益，将开发一个课程，将主题的建议。这项工作将有助于本科生和研究生的教育。本科生将参加一个特殊目的的工作学习计划。

The objective of this EArly-Concept Grant for Exploratory Research (EAGER) project is to elucidate the cause of sorption hysteresis in hindered adsorbed layers in micropores, which has remained fundamentally unexplained for over 60 years. Two mechanisms are investigated. One consists of a series of snap-through instabilities during the filling or emptying of non-uniform pores, due to the non-uniqueness of the misfit disjoining pressure where the pore thickness passes through integer multiples of the monolayer thickness. The second consists of molecular coalescence, or segregation, within a partially filled layer, either by spinodal decomposition (linear instability of homogeneous filling) or by nucleation at defects or pore openings. At the macroscale, both mechanisms lead to heterogeneous filling or emptying across many parallel pores and large changes in the disjoining pressures calculated from thermodynamics. These changes are an essential part of any physical theory of drying creep and shrinkage. Another goal is to identify from sorption tests the pore size distribution and the internal surface area, and the third goal is the prediction of fluid transport through microporous solids. Sorption hysteresis in microporous solids controls microscale stresses which govern creep and inelastic deformations in and around the micropores and the energy dissipation during sorption. The energy dissipated by sorption cycles contributes to material damage. These phenomena are of fundamental interest for predicting the damage and creep in all kinds of concrete structures, release of methane from coal deposits, gas sequestration capacity of rock, gas release from shale, etc. A course incorporating the subject of the proposal will be developed. The work will contribute to the education of both undergraduate and graduate students. Undergraduates will be involved on a special-purpose work-study program.