Study on Flow Simulation Method of Fresh Concrete

现浇混凝土流动模拟方法的研究结果总结如下：改进了剪切箱试验，该试验可适用于从湿拌混凝土到相对干拌混凝土的广泛流变特性。为了测量简便，设计了小型剪切箱试验，并去掉了影响惯性的配重。根据水泥浆和砂浆的测试结果，验证了材料的剪切应变依赖性能，特别是添加细骨料或偏析控制剂时。基于剪切应变依赖模型的粘塑性有限元流动模拟结果，分析了剪切应变硬化现象。此外，还讨论了压力或过渡的影响，并建立了模型。粘塑性悬浮单元法（VSEM）流动模拟的改进首先，对粘塑性悬浮单元法进行了改进，考虑了旋转运动。根据流动模拟结果，验证了考虑壁面摩擦和狭窄空间阻塞的旋转运动的评价，并引入二维粗骨料节点的虚拟半径，使基质通过一对阻塞的粗骨料流出。根据离析试验的模拟结果，给出了砂浆流出量随配合比的变化规律。此外，为了讨论集料的形态，还引入了集料悬吊单元连接的集料节点。l流试验的二维模拟结果表明，随着屈服值和塑性粘度的降低，骨料形状的影响增大。

The results obtained in this research on the flow simulation method of fresh concrete are summarized as follows :1. Measurement and Modeling of Rheological Properties by Shear TestThe shear box test, which can be applied to the wide range of rheological properties from wet-mixed to relatively dry-mixed concrete, has been improved. Small sized shear box test was designed for the sake of simple measurement, and the counter weight, which is the cause of influence of inertia, was removed. According to the results of measurement with cement paste and mortar, the shear strain dependent properties of materials were verified especially for the addmixing of fine aggregate or segregation control agent.Furthermore, according to the result of flow simulation by viscoplastic finite element method with the shear strain dependent model, the phenomenon of shear strain hardening was represented.Moreover, the influence of pressure or transition was discussed and modelized.2. Improvement of Flow Simulation by Viscoplastic Suspension Element Method (VSEM)First of all, VSEM was improved for consideration of rotational motion. According to the result of flow simulation, the evaluation considering rotational motion for the friction on walls and the blockage in narrow space was verifiedFurthermore, the virtual radius for 2-dimensional coarse aggregate nodes was introduced in order to let the matrix flow out through a couple of blocking coarse aggregates. According to the result of simulation of segregation test, the change of amount of flow out mortar with mix proportion was represented.Moreover, the connected aggregate nodes with aggregate suspension elements was introduced in order to discuss the shape of aggregates. According to the result of 2-dimensional simulation of L-flow test, it was clarified that the influence of the shape of aggregates increases with decrease of yield value and plastic viscosity.