Analysis of Time-variant Nano- and Microscopic Mechanisms for Modelling the Meso- and Macroscopic Segregation Stability of Concrete Subject to Vibration

时变纳米和微观机制分析，用于模拟振动混凝土细观和宏观离析稳定性

• 批准号: 387093558
• 负责人: Professorin Dr. Nadja-Carola Bigall
• 金额: --
• 依托单位: Institut für Physikalische Chemie
• 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 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/387093558?language=en
• 关键词: Analysis; Time; variant; Nano; Microscopic

Innovative processing techniques in concrete construction, such as 3D printing or modern and filigree concrete structures, place high demands on the workability of the concrete used. In general, the trend in concrete construction is always towards softer and more flowable concrete. However, the flowability and the stability of a concrete represent competing demands, because the use of flowable concrete increases the risk of unintentional separation. The flow behaviour of the concrete and the meso and macroscopic forms of segregation (deaeration, sedimentation, water secretion) in fresh concrete structures, caused by external forces such as gravity, pump pressure or vibration energy, constitute rheology-based processes. The rheological behaviour can be described by the interactions between the continuous (liquid) and the dispersed (solid) phase which are dependent on the partially nanoscale particle morphology, the particle interactions and the chemical properties of the continuous phase. In addition, an interaction with granular aggregates occurs, which has an effect on the macroscopic level. The existing model approaches for describing the load-deformation behaviour for cementitious suspensions represent a promising basis. However, these do not take into account the influence of early-accumulating hydration products from the microstructure. For a description of the load-deformation behaviour and the stability, existing modelling approaches have to be extended by the plastic component, determined by the mechanical behaviour of early hydration products.The identification of the correlations between the properties on the nano- and microscale and the measurable rheological properties as a function of time represents the basis of this proposal. The particle morphology and the physical and electrochemical properties of the carrier fluid at defined times after the addition of water are to be determined analytically. In addition, how these nano- and microscopic characteristics affect measurable rheological properties of the binder suspension will be investigated. A high shear stress, as occurs during concrete casting during vibration effects, results in a significant change in the rheological properties of the paste phase that will be represented via the description of the structural breakdown behaviour of the suspension. Besides the resulting influence of the properties of the paste phase itself, it particularly influences the interaction between the paste phase and the intergranular particles (aggregates). This interaction will be identified during exemplary mortar and concrete investigations by varying the granulometric properties of the aggregate and by varying the structure of the graduation curve. Thanks to this implementation of the multiscale structure of the work programme, all relevant factors will be identified and will serve as input variables in a conceptual model to describe the segregation stability of concrete during vibration effects.

混凝土施工中的创新加工技术，如3D打印或现代和花丝混凝土结构，对所用混凝土的可加工性提出了很高的要求。一般来说，混凝土施工的趋势总是朝着更柔软和更易流动的混凝土方向发展。然而，混凝土的流动性和稳定性代表了相互竞争的需求，因为使用可流动的混凝土增加了意外分离的风险。混凝土的流动行为以及新浇混凝土结构中由重力、泵压或振动能等外力引起的细观和宏观形式的离析（脱气、沉降、泌水）构成了基于流变学的过程。流变行为可以通过连续（液体）和分散（固体）相之间的相互作用来描述，其取决于部分纳米级颗粒形态、颗粒相互作用和连续相的化学性质。此外，与粒状聚集体的相互作用发生，这在宏观水平上具有影响。现有的模型方法用于描述水泥悬浮体的载荷-变形行为是一个有前途的基础。然而，这些都没有考虑到早期积累的水化产物的微观结构的影响。为了描述的负载变形行为和稳定性，现有的建模方法必须扩展的塑料组件，由早期水合products.The确定的力学行为之间的相关性的纳米和微米尺度上的属性和可测量的流变性能作为时间的函数表示的基础上，这一建议。在加水后的规定时间，通过分析确定载液的颗粒形态和物理及电化学性质。此外，这些纳米和微观特性如何影响可测量的流变性能的粘合剂悬浮液将进行研究。高剪切应力，如在混凝土浇注期间在振动效应期间发生的，导致糊状物相的流变性质的显著变化，这将通过描述悬浮液的结构分解行为来表示。除了对糊状物相本身的性质产生影响之外，它特别影响糊状物相和颗粒间颗粒（聚集体）之间的相互作用。这种相互作用将在示例性砂浆和混凝土调查期间通过改变骨料的粒度特性和通过改变分级曲线的结构来识别。由于实施了工作方案的多尺度结构，所有相关因素都将得到确定，并将作为概念模型的输入变量，以描述振动效应期间混凝土的离析稳定性。