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Effects of Partail Replacement of Cement by Fly Ash on the Rheological Property and Workability of Flowable Concrete
The pozzolanic materials, such as fly ash and slag, are often added into high performance concrete (HPC) to improve the workability, economy and durability. Because of the discrepancy between each region, the application and restriction of these materials are variable. Fly ash from coal-burning power plants is generally used to be a supplementary material in concrete because of its pozzolanic and cementitious properties. It can take the place of cement or fine aggregate or both, particularly the cement for economic purpose. What the influence of fly ash on the flowability of high-flowability concrete is the key-point of this research. In this study,the high- flowability concrete which water-cementitious ratio created 0.3 and 0.5 is investigated. The substitute ratio that fly ash takes the place of cement by weight is the only test variable. It is designed to be 10, 20, 30 and 50% to investigate the optimum ratio for the fresh HPC. Two-point test was adopted as major method to determinate the workability of fresh concrete, while the slump-flow, flow time and V-funnel test were also performed for comparison. Test results show that in different water-cementitious ratio yield stress and plastic viscosity of high-flowability concrete change with the time and the substitute ratio dissimilar. However, the variation of yield stress trends to a stable increasing with the raising substitute ratio as the water-cementitious ratio is 0.3, but this tendency does not find as the water-cementitious ratio is 0.5. In a word, in addition to the time factor, the effects of fly ash on the initial flow and the following viscous flow should be combined together when considering the influence on the flowability of the high-workability concrete containing fly ash.
|Appears in Collections:||土木工程學系所|
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