Thixotropy and Formwork Pressure of SCC

摘要：在过去的二十年中，自固结混凝土（SCC）已经彻底改变了美国和世界大部分地区混凝土施工的方式。然而，它的高流动性加上更快的浇筑速度，导致人们担心使用当前SCC模板设计实践是否足够。因此，SCC模板通常在设计时假定将实现全液压头，并且与振动混凝土相比，该模板使用了更多的结构连接。这是一个值得关注的问题，因为模板成本可能占建筑成本的很大一部分。触变性过程中发生的粘度恢复会影响混凝土的和易性，因此这可能会影响许多施工过程。本研究的目的是促进对流动引起的结构变化与胶凝材料在水化早期（凝固前）流变学之间关系的理解。第一阶段的研究重点是通过研究絮凝机理来获得对触变现象的基本认识。从这种理解，之间的关系模板压力，触变性和流变性将确定。在本研究的第二阶段，将应用计算流体力学（CFD）方法来模拟水泥浆体和砂浆的流动。粘度函数将与CFD方法相结合，以提供水泥浆和砂浆从坍落锥中流动的可视化模拟。

Abstract: CMS- 0625606During the last two decades, self-consolidating concrete (SCC) has revolutionized the way that concrete construction is performed in the United States and throughout most of the world. However, its high fluidity coupled with the use of faster casting rates has led to concerns about the adequacy of using current formwork design practices for SCC. As a result, SCC formworks are often designed with the assumption that full liquid pressure head will be achieved and the forms are constructed using more structural ties than those constructed for vibrated concrete. This is a significant concern since formwork costs can represent a significant percent of the construction costs. The recovery of viscosity that occurs during thixotropy can affect the workability of the concrete, and thus this may affect a number of construction processes. The objective of this research is to advance the understanding of the relationship between flow-induced structural changes and the rheology of cementitious material during the early stages (before setting) of hydration. The first phase of the proposed research focuses on gaining a fundamental understanding of the thixotropic phenomena through studying flocculation mechanisms. From this understanding, the relationship among formwork pressure, thixotropy, and rheology will be determined. In the second phase of the proposed research, computational fluid dynamics (CFD) methods to simulate the flow of cement paste and mortar will be applied. The viscosity function will be coupled with CFD methods in order to provide visual simulations of the flow of cement paste and mortar from a slump cone.