以改良式混凝土質流儀量測新拌混凝土質流行為之研究

A Study on Using Modified Concrete Rheometer to Measure the Rheological Behavior of Fresh Concrete

本研究開發改良式混凝土質流儀（MCR），係依據現有的混凝土質流儀進行改良，其中外桶與葉片的間距為最大粗粒料粒徑的6.4 倍以降低兩者互相的影響，並以數種低轉速（0.003 rev/sec 以上）直接量測新拌混凝土的降伏扭矩。本研究量測40 組新拌混凝土的降伏扭矩及黏度尤其是針對自充填混凝土（SCC），並且與既有的混凝土工作性測試法進行比較，試驗結果顯示所量測的降伏扭矩皆為正值且再現性較單一轉速為佳。飛灰與爐石粉取代水泥量影響粉體系自充填混凝土的質流行為，含增黏劑的自充填混凝土因總粉體量小且水膠比較大，其黏度與降伏扭矩大部份比粉體系自充填混凝土略小且數值範圍較為集中，故工作性的穩定性較佳。而改良式混凝土質流儀不僅建立普通混凝土的坍度與降伏扭矩、黏度之關係，並且可區分大部份自充填混凝土之分佈範圍，因此可作為檢測新拌混凝土工作性之品管儀器。

This study developed a modified concrete rheometer (MCR) based on existing concrete rheometer. The gape between inner cylinder wall and the tip of vane is 6.4 times the diameter of the largest coarse aggregates for the purpose of reducing the interaction, and the rheometer measures yield torque directly at different low rotational speed (above 0.003 rev/sec). This study also measured the yield torque and viscosity of forty fresh concrete mixtures, especially for self-compacting concrete (SCC), and compares with the results from other workability tests. The test results showed that all the values of concrete yield torque are positive and the repeatability of data is better than one fixed rotational speed. The rheological behavior of powder type-SCC will be influenced by the replacement amount of fly ash and GGBF slag powder. With smaller amount of powder and larger water to binder ratio (w/b), the viscosity and yield torque of SCC containing Viscosity modifying agent (VMA) are slightly smaller than that of powder type-SCC, and their values tend to concentrate in a certain range, thus the workability of SCC containing VMA is much more stable. Besides, MCR not only can establish the relationship between slump and yield torque of conventional slump concrete, but also different types of SCC, therefore, it can be used as QC instrument to perform inspection of the workability of fresh concrete.