Properties of Self-Consolidating Concrete Containing Type F Fly Ash

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Properties of Self-Consolidating Concrete Containing Type F Fly Ash (thesis)

Author: Raissa P. Douglas | Size: 1.9 MB | Format: PDF | Publisher: PCA | Year: 2004 | pages: 84

Since the introduction of self-consolidating concrete (SCC) in Japan during the late 1980’s, acceptance and usage of this concrete in the construction industry has been steadily gaining momentum. In the United States, the usage of SCC has been spearheaded by the precast concrete industry. Good SCC must possess the following key fresh properties: filling ability, passing ability, and resistance to segregation. In order to reduce segregation, SCC mixes are typically designed with high powder contents, and contain chemical admixtures such as superplasticizers and viscosity modifying admixtures (VMA). This tends to increase the material cost of SCC, however one way to reduce the material cost is through adequate mix proportioning and the addition of supplementary cementitious materials such as fly ash. Millions of tons of fly ash are generated annually in Illinois; however Class F fly ash is more often landfilled than used. Incorporation of Class F fly ash in self-consolidating concrete as a means to replace portions of cement can decrease the cost of SCC, as well as further the sustainable development of concrete. An experimental program, aimed at investigating the behavior of SCC containing Class F fly ash has been carried out. The fresh state properties of the concrete were assessed using methods of segregation and flow. The rheology of the paste matrix was also characterized and compared with a previously developed paste rheology model. Finally, some hardened state properties of the concrete were evaluated. The objective of this research is to improve the understanding of the properties of SCC containing Class F fly ash and to provide information that could be used towards the commercialization of such a concrete. The results indicate that it is possible to develop a SCC containing Class F fly ash that is high performing in its fresh state. Furthermore, the addition of fly ash was shown to reduce superplasticizer dosage, increase workability, and increase overall chloride permeability resistance. In addition, it was determined that the difference of densities between the aggregate and matrix influence the results of a previously developed paste rheology model.

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