Transition zone studies of new-to-old concrete with different binders

Abstract

The weak transition zone between new and old concrete controls many properties of repaired concrete. The transition zone between aggregates and cement pastes of normal concrete has been studied by a number of researchers. But to date, there is little information available about the interfacial zone between new and old concrete. In this paper, major properties of the transition zone between new and old concrete with different binders were studied by using both scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The bond strength was also investigated. The test results show that the binder is a vital factor, which affects the morphology (size and shape), mineralogy and the microstructure of the transition zone in repaired concrete.