Thixotropy and Formwork Pressure of SCC

摘要：CMS-0625606在过去的二十年里，自密实混凝土(SCC)彻底改变了美国和世界大部分地区的混凝土施工方式。然而，它的高流动性加上使用更快的浇注速度，导致人们担心使用当前的模板设计实践是否足以用于SCC。因此，SCC模板的设计通常假设将达到完全的液体压力水头，并且模板使用比振动混凝土更多的结构纽带。这是一个重要的问题，因为模板成本可能占建筑成本的很大百分比。在触变过程中发生的粘度恢复可能会影响混凝土的工作性，因此可能会影响许多施工过程。这项研究的目的是促进对水化早期(凝结前)胶凝材料的流变性与流动引起的结构变化之间的关系的理解。第一阶段的研究重点是通过研究絮凝机理对触变现象有一个基本的了解。根据这一理解，将确定模板压力、触变性和流变学之间的关系。在拟议研究的第二阶段，将应用计算流体动力学(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，以提供从坍塌锥体中流出的水泥浆体和砂浆的可视化模拟。

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.