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標題: 飛灰取代部分水泥對流動性混凝土質流性質與工作性之影響
Effects of Partail Replacement of Cement by Fly Ash on the Rheological Property and Workability of Flowable Concrete
作者: 吳秋濃
關鍵字: Rheology
Two-point test
Fly ash
V 型流度儀
出版社: 土木工程學系
摘要: 高性能混凝土的組成材料,因考量工作性、經濟性與耐久性之需求,而常添加波索蘭材料,如飛灰、爐石粉及矽灰等。基於材料之區域特性與產出,各地的運用策略與限制也各自不同。其中飛灰係以燃煤為動力的工業副產品,具有波索蘭反應特性,最常作為混凝土摻料。其使用法有:取代水泥、取代細骨材或二者皆取代,其中以取代水泥應用較廣。本文即在探討飛灰取代水泥對流動性混凝土新拌性質的影響。 本研究針對水膠比為0.3及0.5兩種流動性混凝土,以飛灰取代比例為試驗變數,分別取10、20、30、50%四種。工作性之測定以質流性質的兩點試驗法為主,並輔以坍流度、流動時間及V-funnel test,來探討在不影響硬固混凝土性質下,最佳流動性之飛灰取代量。研究結果顯示:不同飛灰取代比例對流動性之影響,隨拌合後時間增加而有不同程度的變化。再者,在不同的水膠比情形下,混凝土降伏應力及塑性黏滯係數隨著飛灰取代比例增加而有不同的改變。然而,單獨就降伏應力而言,在0.3水膠比時降伏應力會隨著飛灰取代量的增加而穩定成長,但在0.5水膠比時則不然。換言之,飛灰的添加對於流動性的影響,除應考量時間因素外,還須注意其對初始流動與後續黏滯流動不同的貢獻。
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.
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