Ley-Hernandez Aida Margarita, Lapeyre Jonathan, Cook Rachel, Kumar Aditya, Feys Dimitri
Department of Civil, Architectural, and Environmental Engineering, Department of Materials Science and Engineering, Department of Materials Science and Engineering, Department of Materials Science and Engineering, and Department of Civil, Architectural, and Environmental Engineering, Missouri University of Science and Technology (S&T), Rolla, Missouri 65409-0340, United States.
ACS Omega. 2018 May 9;3(5):5092-5105. doi: 10.1021/acsomega.8b00097. eCollection 2018 May 31.
The hydration of cement is often modeled as a phase boundary nucleation and growth (pBNG) process. Classical pBNG models, based on the use of isotropic and constant growth rate of the main hydrate, that is, calcium-silicate-hydrate (C-S-H), are unable to explain the lack of any significant effect of the water-to-cement (/) ratio on the hydration kinetics of cement. This paper presents a modified form of the pBNG model, in which the anisotropic growth of C-S-H is allowed to vary in relation to the nonlinear evolution of its supersaturation in solution. Results show that once the supercritical C-S-H nuclei form, their growth remains confined within a region in proximity to the cement particles. This is hypothesized to be a manifestation of the sedimentation of cement particles, which imposes a space constraint for C-S-H growth. In pastes wherein the sedimentation of cement particles is disrupted, the hydration kinetics are no longer unresponsive to changes in /. Unlike C-S-H, the ions in solution are not confined, and hence, the supersaturation-dependent growth rate of C-S-H diminishes monotonically with increasing /. Overall, the outcomes of this work highlight important aspects that need to be considered in employing pBNG models for simulating hydration of cement-based systems.
水泥的水化通常被模拟为相边界成核与生长（pBNG）过程。基于主要水化物即硅酸钙水化物（C-S-H）的各向同性和恒定生长速率的经典pBNG模型，无法解释水灰比（/）对水泥水化动力学缺乏显著影响的现象。本文提出了一种改进形式的pBNG模型，其中允许C-S-H的各向异性生长随其在溶液中的过饱和度的非线性演化而变化。结果表明，一旦超临界C-S-H核形成，它们的生长就会局限在靠近水泥颗粒的区域内。据推测，这是水泥颗粒沉降的一种表现，它对C-S-H的生长施加了空间限制。在水泥颗粒沉降受到干扰的浆体中，水化动力学不再对/的变化无响应。与C-S-H不同，溶液中的离子不受限制，因此，C-S-H的过饱和度依赖生长速率随/的增加而单调减小。总的来说，这项工作的结果突出了在使用pBNG模型模拟水泥基体系水化时需要考虑的重要方面。
