Simulation based modelling of time- and shear-dependent disperse and rheological properties of cement suspensions

基于仿真的水泥悬浮液时间和剪切相关分散和流变特性的建模

• 批准号: 387066140
• 负责人: Professor Dr.-Ing. Harald Budelmann
• 金额: --
• 依托单位: Institut für Baustoffe, Massivbau und Brandschutz
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2017
• 资助国家: 德国
• 起止时间: 2016-12-31 至 2020-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/387066140?language=en
• 关键词: Simulation; based; modelling; time; shear

The aim of the project is to develop enhanced constitutive models for the prediction of rheological properties of cementitious materials based on chemical and physical particle and fluid characteristics. Due to its fundamental basis the modelling approach exhibits a general validity and applicability. Bridging the gap between fundamental insights into chemical and physical processes at nano as well as micro scale and the macroscopic flow behavior, the project makes a contribution for overcoming limitations of existing constitutive rheological models. Thereby, a more reliable simulation and modelling of concrete flow even for complex processing steps with time-variant shear history, such as pumping, 3D printing or spraying, is enabled. To that end, the time- and shear-dependent disperse and rheological properties of cementitious suspensions are investigated and modelled based on fundamental material properties and interactions with the help of coupled CFD-DEM simulations. With the help of the simulations, the basic interactions depending on numerous chemical and physical particles and fluid characteristics, mixture composition and processing parameters can be modelled comprehensively for the first time. New time-dependent contact models are developed and used for the coupled CFD-DEM simulations. The results of the simulation environment are calibrated and validated by different experiments. The properties of particles and fluid relevant for the simulations are investigated in cooperation with other working groups. Therefore, different reacting and non-reacting technical and model particulate systems are used. The disperse and the rheological properties of the suspensions are characterized comprehensively. Relevant particle and fluid characteristics are investigated by rotational and oscillation rheometer tests. The microstructure effect on the rheological properties is described by the particle agglomeration behavior. Therefore, the agglomeration state and the rheological properties are characterized for different shear rates, time steps and shear histories with and without regard for hydration effects. The particle size distribution and the agglomeration state of the pastes are determined under shear conditions by a laser backscattering method integrated into a new coaxial cylinders rheometer setup. Based on the simulation and experimental results the time- and shear-dependent microstructure effects are implemented into existing constitutive models enabling the consideration of thixotropic effects and ageing effects due to cement hydration. Being a key parameter for constitutive models and multi-scale modelling, a special focus will be on the determination of local shear rates acting on the paste phase. The approach enables to capture realistic shear parameters for the simulations and experiments at micro scale, hence allowing a more reliable scale-up and modelling.

该项目的目的是开发基于化学和物理颗粒和流体特性的增强型本构模型，用于预测胶凝材料的流变性能。由于其基本基础，该建模方法具有普遍的有效性和适用性。该项目弥合了纳米和微米尺度下化学和物理过程的基本见解与宏观流动行为之间的差距，为克服现有本构流变模型的局限性做出了贡献。因此，即使对于具有时变剪切历史的复杂处理步骤，例如泵送、3D打印或喷涂，也能够实现混凝土流动的更可靠的模拟和建模。为此，时间和剪切相关的分散和流变性能的水泥悬浮液的研究和建模的基础上的基本材料特性和相互作用的帮助下耦合的CFD-DEM模拟。借助模拟，可以首次全面模拟取决于众多化学和物理颗粒以及流体特性、混合物成分和工艺参数的基本相互作用。开发了新的时间相关接触模型，并用于耦合CFD-DEM模拟。通过不同的实验对仿真环境的结果进行了校准和验证。与其他工作组合作研究了与模拟相关的粒子和流体的性质。因此，使用不同的反应和非反应技术和模型颗粒系统。全面表征了悬浮液的分散性和流变性。相关的颗粒和流体特性进行了研究，通过旋转和振荡流变仪测试。微观结构对流变性能的影响通过颗粒团聚行为来描述。因此，团聚状态和流变性能的特征在于不同的剪切速率，时间步长和剪切历史，并不考虑水合作用。在剪切条件下，通过激光背散射方法集成到一个新的同轴圆筒流变仪设置的粒度分布和团聚状态的糊确定。基于模拟和实验结果的时间和剪切相关的微观结构的影响实施到现有的本构模型，使考虑由于水泥水化的触变效应和老化效应。作为本构模型和多尺度建模的关键参数，将特别关注作用于膏体相的局部剪切速率的确定。该方法能够捕获真实的剪切参数的模拟和实验在微观尺度上，从而允许一个更可靠的放大和建模。