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APS -APS March Meeting 2017 - Event - Failure of cement hydrates: freeze-thaw and fracture

机译:APS -APS 2017年3月会议-活动-水泥水合物的破​​坏:冻融和断裂

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Mechanical and viscoelastic behavior of concrete crucially depends on cement hydrates, the ``glue'' of cement. Even more than the atomistic structure, the mesoscale amorphous texture of cement hydrates over hundreds of nanometers plays a crucial role for material properties. We use simulations that combine information of the nano-scale building units of cement hydrates and on their effective interactions, obtained from atomistic simulations and experiments, into a statistical physics framework for aggregating nanoparticles.Our mesoscale model was able to reconcile different experimental results ranging from small-angle neutron scattering, SEM, adsorption/desorption of N$_{2}$, and water to nanoindentation and gain the new fundamental insights into the microscopic origin of the properties measured [1]. Our results suggest that heterogeneities developed during the early stages of hydration persist in the structure of C-S-H, impacting the rheological and mechanical performance of the hardened cement paste. In this talk I discuss recent investigation on failure mechanism at the mesoscale of hardened cement paste such as freeze-thaw and fracture. Using correlations between local volume fractions and local stress we provide a link between structural and mechanical heterogeneities during the failure mechanisms.1. Ioannidou K. et al, The mesoscale texture of cement hydrates, Proceedings of National Academy of Science USA, 113 (8), 2029-2034 (2016)
机译:混凝土的机械和粘弹性行为主要取决于水泥水合物,即水泥的``胶水''。水泥水合物的中尺度无定形织构甚至超过了原子结构,对材料性能起着至关重要的作用。我们使用模拟方法将水泥水合物的纳米级建筑单元及其有效相互作用的信息结合起来,这些信息是从原子模拟和实验获得的,并用于统计物理框架中聚集纳米颗粒。我们的中尺度模型能够调和不同的实验结果,包括小角中子散射,SEM,N $ _ {2} $的吸附/解吸以及水对纳米压痕的影响,并获得了对所测量特性的微观起源的新的基本见解[1]。我们的结果表明,水合早期形成的异质性在C-S-H的结构中仍然存在,影响了硬化水泥浆的流变性和机械性能。在本次演讲中,我将讨论有关硬化水泥浆的中等尺度破坏机制的最新研究,例如冻融和断裂。利用局部体积分数与局部应力之间的相关性,我们在失效机理过程中提供了结构和机械异质性之间的联系。 Ioannidou K.等人,水泥水合物的中尺度结构,美国国家科学院院刊,113(8),2029-2034(2016)

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