Thixotropy and Formwork Pressure of SCC

摘要：CMS-0625606在过去的二十年里，自固结混凝土（SCC）已经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，其高流动性加上使用更快的浇注速度，导致人们对SCC使用当前模板设计实践的充分性表示担忧。因此，SCC模板的设计通常假设将实现全液压头，并且模板使用比振动混凝土更多的结构拉杆来建造。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一部分。在触变性过程中发生的粘度恢复会影响混凝土的可加工性，因此这可能会影响许多施工过程。本研究的目的是推进流动引起的结构变化和流变性的胶凝材料在早期阶段（凝固前）的水化之间的关系的理解。建议的研究的第一阶段的重点是通过研究絮凝机制获得对触变现象的基本理解。从这一认识出发，将确定模板压力、触变性和流变性之间的关系。在拟议研究的第二阶段，将应用计算流体动力学（CFD）方法来模拟水泥浆和砂浆的流动。粘度函数将与计算流体动力学方法相结合，以提供水泥浆和砂浆从坍落度筒流动的可视化模拟。

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.