Effect of Rheology of SCC on Bond Strength of Ribbed Reinforcement Bars

Abstract

SCC can have very different rheological properties depending on the application and local mix design traditions. By definition, SCC should encapsulate the reinforcement bars to ensure proper bond strength, however, variations in bond strength may at least theoretically occur dependent on the rheological properties and the flow characteristics history near the individual bar. Especially, the bond strength may be questioned for SCC with a slump flow in the range 500-580 mm which is often used to obtain good control of flowing concrete as well as high segregation resistance. This paper presents the results of an experimental program investigating the relationship between the rheological parameters yield stress and plastic viscosity and bond strength of reinforcement bars. A reference conventional slump concrete requiring vibration to consolidate and several SCCs of equivalent strength class but with varying rheological parameters as measured by the 4CRheometer were prepared. Batches of 250 liters were cast into a formwork containing 12 mm diameter ribbed reinforcement bars fixed horizontally. The distance of SCC flow in the formwork was 2.5 m. Bond and compressive strengths were tested after 7 days of curing. The results indicate that the bond strength is not significantly influenced by the rheological properties of SCC and that the bond strength corresponds to that of conventional concrete.