Effects of steel and polymer fiber on the rheological behavior and processing parameters of cement-based materials in the context of 3D-printing by layered extrusion – printFRC

分层挤出 3D 打印中钢和聚合物纤维对水泥基材料流变行为和加工参数的影响 â printFRC

• 批准号: 387152958
• 负责人: Professor Dr.-Ing. Viktor Mechtcherine
• 金额: --
• 依托单位: Institut für Baustoffe
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/387152958?language=en
• 关键词: Effects; steel; polymer; fiber; rheological

Purposeful design and control of the rheological properties of cementitious materials is the basis for development of new technologies such as additive construction (AC), which not only enables the speedy, economic, formwork-free construction of buildings and other structures, but also constitutes a highly important step from digital planning to digital construction (Construction Industry 4.0). The main objective of the project at hand is to contribute comprehensively to the creation of the scientific framework for quantification of the effects of concrete composition on the rheological and processing properties relevant to AC. The research program is divided into three segments: Experimental Rheology, Processing Parameters and Modelling. Experimental Rheology investigations will start with cement paste for selection of the most suitable compositions, including the choice of additives, in the context of AC. In the next step, the influences of shape, size and packing density of aggregates as well as firbe stiffness and content will be investigated as a basis for analytical modelling of the rheological properties. Dynamic rheological measurements in the steady state and static measurements of structural build-up at rest will be carried out using rate-controlled rheometers with appropriate testing regimes. Furthermore, as a physical basis for the derivation of the constitutive relationships for contacts between discrete elements, force-displacement relationships for inter-aggregate contact forces with cement paste in-between will be investigated. The segment Process Parameters focuses on the AC-related properties - extrudability and buildability - including the development of appropriate experimental on-line and off-line methods. The results obtained will be compared with the results of rheometry to identify the critical lower and upper limits of rheological parameters for various stages of AC. The Modelling segment includes analytical and numerical modelling of the rheological behaviour of fresh cement paste, mortar and concrete in the context of AC processes. Based on the experimental results of the first segment, existing models to describe the fresh properties of cementitious materials will be validated and, if needed, further developed analytically using multi-scale approaches. Thixotropic and transient behaviour of cementitious materials will be modelled taking into account the magnifying effect of mesoscopic constituents such as aggregates and fibres. The researchers own DEM model will be extended by implementing thixotropy and time-dependency. Next, the effects of shape and size of aggregates will be introduced using clump logic. The numerical model will be validated by virtual buildability tests and comparing these results to the experimental ones. With respect to AC the DEM model can be eventually be employed as a tool both for supporting purposeful material design and for the reliable configuration of process parameters.

有目的的设计和控制胶凝材料的流变特性是开发新技术的基础，例如增材施工（AC），它不仅可以实现快速，经济，无模板的建筑和其他结构的施工，而且还构成了从数字规划到数字施工的非常重要的一步（建筑业4.0）。目前该项目的主要目标是为量化混凝土成分对与AC相关的流变学和加工性能的影响的科学框架的创建做出全面贡献。研究计划分为三个部分：实验流变学，加工参数和建模。实验流变学研究将从水泥浆开始，以选择最合适的成分，包括添加剂的选择，在AC的背景下。下一步，将研究集料的形状、大小和堆积密度以及纤维刚度和含量的影响，作为流变特性分析建模的基础。稳定状态下的动态流变学测量和静止状态下结构积累的静态测量将使用具有适当测试制度的速率控制流变仪进行。此外，作为离散单元之间接触本构关系推导的物理基础，将研究水泥膏体之间骨料间接触力的力-位移关系。工艺参数部分侧重于交流相关特性-可挤压性和可建造性-包括开发适当的在线和离线实验方法。获得的结果将与流变学的结果进行比较，以确定AC各阶段流变参数的临界下限和上限。建模部分包括在AC过程背景下新鲜水泥浆、砂浆和混凝土的流变行为的分析和数值模拟。基于第一部分的实验结果，现有的描述胶凝材料新特性的模型将得到验证，如果需要，将使用多尺度方法进一步开发分析。胶凝材料的触变和瞬态行为将被模拟，考虑到介观成分的放大效应，如聚集体和纤维。研究人员将通过实现触变性和时间依赖性来扩展自己的DEM模型。接下来，聚集体的形状和大小的影响将引入使用团块逻辑。数值模型将通过虚拟可建性测试进行验证，并与实验结果进行比较。对于AC， DEM模型最终可以作为一种工具来支持有目的的材料设计和可靠的工艺参数配置。