Thixotropy and Formwork Pressure of SCC

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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.