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Keywords
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Self-Consolidating Concrete, Rheology, Yield Stress, Plastic Viscosity, Thixotropy, Packing Density, Tuff powder, Paste Film Thickness, Mortar Film Thickness
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Abstract
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This research investigates the physical influence of internal components of Self-Consolidating Concrete (SCC) on its rheological properties and thixotropy, focusing on packing density and paste/mortar film thickness. It also examines SCC mixtures containing tuff as a cement substitute compared to silica fume. The study is divided into two steps. In the first step, the effect of internal components on both fresh and hardened states of SCC was analyzed through three groups of mixtures including varying aggregate distributions (aggregate gradation curve exponent (𝑛) of 0.2, 0.25, 0.3, and 0.35), cement replacement with 15% tuff powder and 8% silica fume as Supplementary Cementitious Material (SCM), and cement content adjusted by ±5%, maintaining constant water content. Tests evaluated fresh-state properties (workability, rheology, thixotropy, and packing density) and hardened-state properties (compressive strength and Ultrasonic Pulse Velocity) of SCC mixtures. The second step explored relationships between workability, rheology, packing density, and thixotropy. It also examined the effects of paste and mortar film thickness on yield stress, plastic viscosity, and thixotropy. Results identified an optimal gradation exponent of 0.3 for the lowest rheological properties and highest packing density. Using 15% tuff as cement substitute increased yield stress and plastic viscosity by 100% and 14%, respectively, but reduced thixotropy by 12% and packing density by 2%. Additionally, increased paste film thickness (PFT) reduced plastic viscosity but increased thixotropy, while increased mortar film thickness (MFT) had the opposite effect. No significant relationship was observed between PFT/MFT and yield stress.
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