Investigation of the Bond between Concrete Substrate and ECC Overlays

Abstract

Rigid concrete overlays have been used for smoothing damaged surfaces and/or restoring or improving the mechanical capacity of bridge decks for many years. However, engineered cementitious composites (ECCs), which demonstrate superior ductility with high strength and improved durability characteristics, are an attractive alternative to conventional overlay materials if a strong mechanical bond is formed between the overlay and the substrate material. An experimental study was performed to evaluate the bond strength between ECC overlay and an ordinary concrete substrate with smooth and rough surface textures. Microsilica concrete (MSC), generally used as an overlay material, was also prepared as a control mixture. ECC and MSC overlay mixtures were cast over the concrete substrate to determine bonding performance. Slant shear and splitting prism tests were performed with MSC and two ECC mixtures. The experimental results show that when ECC is used as an overlay material, bond strength is significantly increased compared to MSC. Under compression loading (slant shear test), the bond-strength properties of layered ECC substrate concrete cylinder specimens were greater than the strength of substrate concrete with compressive strength of around 30 MPa. However, in the case of layered MSC substrate concrete cylinder specimen, failure consistently occurred at the interface.