Physics of AmoRphous and Inorganic Solids Laboratory (PARISlab), Department of Civil and Environmental Engineering, University of California, Los Angeles, CA 90095, USA.
Physics of AmoRphous and Inorganic Solids Laboratory (PARISlab), Department of Civil and Environmental Engineering, University of California, Los Angeles, CA 90095, USA; Laboratory for the Chemistry of Construction Materials (LC(2)), Department of Civil and Environmental Engineering, University of California, Los Angeles, CA 90095, USA.
J Colloid Interface Sci. 2019 Apr 15;542:339-346. doi: 10.1016/j.jcis.2019.02.022. Epub 2019 Feb 7.
When subjected to a sustained load, jammed colloidal gels can feature some delayed viscoplastic creep deformations. However, due to the long timescale of creep (up to several years), its modeling and, thereby, prediction has remained challenging. Here, based on mesoscale simulations of calcium-silicate-hydrate gels (CSH, the binding phase of concrete), we present an accelerated simulation method-based on stress perturbations and overaging-to model creep deformations in CSH. Our simulations yield a very good agreement with nanoindentation creep tests, which suggests that concrete creep occurs through the reorganization of CSH grains at the mesoscale. We show that the creep of CSH exhibits a logarithmic dependence on time-in agreement with the free-volume theory of granular physics. Further, we demonstrate the existence of a linear regime, i.e., wherein creep linearly depends on the applied load-which establishes the creep modulus as a material constant. These results could offer a new physics-based basis for nanoengineering colloidal gels featuring minimal creep.
当受到持续负载时，被卡住的胶体凝胶可能会出现一些延迟的黏塑性蠕变变形。然而，由于蠕变的时间尺度很长（长达数年），其建模，因此，预测一直具有挑战性。在这里，基于钙硅酸盐水合物凝胶（CSH，混凝土的结合相）的介观模拟，我们提出了一种基于应力扰动和过时效的加速模拟方法来模拟 CSH 中的蠕变变形。我们的模拟与纳米压痕蠕变测试非常吻合，这表明混凝土蠕变是通过介观尺度上的 CSH 颗粒的重组发生的。我们表明，CSH 的蠕变与时间呈对数关系——与颗粒物理的自由体积理论一致。此外，我们证明了线性阶段的存在，即蠕变与施加的负载呈线性关系，这将蠕变模量确立为材料常数。这些结果可能为具有最小蠕变的胶体凝胶的纳米工程提供新的基于物理的基础。
