Testing Segregation and Other Rheological Properties of Self-Consolidating Concrete (SCC)

Abstract

Self-consolidating concrete (SCC) is a new type of high performance concrete that flows under its own weight, passes through intricate geometrical configurations, and fills the formwork without vibration and consolidation. Compared with normal concrete mixes, the composition and the rheological properties of SCC should be closely controlled in order to satisfy the fresh property requirements simultaneously. Moreover, the segregation resistance of self-consolidating concrete (SCC) is more sensitive to small variations of its properties. Segregation refers to movement of coarse aggregate relative to the mortar. Static segregation occurs when the concrete is at rest and the coarse aggregate sinks in the mortar. Dynamic segregation occurs when the concrete is flowing and the coarse aggregate lags behind the mortar. To study segregation and design an SCC mix, which is robust against small variations in raw materials, it is critical to be able to quickly quantify static and dynamic segregation and stability robustness. In this study, a modified Segregation Probe is introduced as a simple and fast method for testing static segregation and stability robustness of fresh concrete. On the other hand, Flow Trough was developed to measure dynamic segregation. It was found that mixture properties, such as higher paste volume, lower superplasticizer percentage by weight of cement, lower slump flow, smaller aggregate size, better gradation, and higher aggregate packing density may improve robustness and dynamic stability. The effects of various aggregate properties on SCC rheology were investigated. It was found that lower superplasticizer dosage, higher aggregate volume, higher fine aggregate to coarse aggregate ratio, smaller aggregate size and lower aggregate packing density may increase yield stress of SCC mixture. Aggregate size had insignificant effect on plastic viscosity. Mixtures with Low slump flow (slump flow value less than 580 mm (23 in) in this study) exhibited anti-thixotropy manner, while mixtures with higher slump flow showed thixotropy manner.