Bond behavior of self-consolidating concrete with mineral and chemical admixtures

Self-consolidating concrete (SCC) is known for its excellent deformability, high resistance to segregation, and use in congested reinforced concrete structures characterized by difficult casting conditions without applying vibration. Research has been conducted on the development of SCC using high volumes of supplementary cementing materials (SCM) (such as fly ash and slag) and viscosity modifying admixtures (VMA). The bond characteristics of such SCCs are very important for their application in practical construction. An extensive investigation was conducted to determine the bond strength between deformed reinforcing steel bar and SCM and VMA based SCC as well as normal concrete (NC). Bond tests were conducted using a specially developed pullout test. The SCC pullout specimens were cast without applying any consolidation, whereas the NC specimens were cast by conventional practice with consolidation and vibration. It was found that the reduction in bond strength due to bleeding and inhomogeneous nature was less in SCC compared to NC. Although the variation in bond strengths at different casting elevations was observed in SCC, the extent was less significant than that of NC. SCC also exhibited a less significant top-bar effect compared to NC. This can be attributed to the more consistent nature of SCC and its superior filling capability. Performance of various code based and other existing bond equations are validated through experimental results illustrating the influence of concrete types (either SCC of different types or NC).