The Microstructure of Epoxy Bonded Steel-To-Concrete Joints

摘要

Exposure tests were carried out on concrete beams (508mm x 102mm) strengthened by a single mild steel plate bonded to the surface of the concrete using a structural grade epoxy adhesive containing a siliceous filler. Visual examination showed that corrosion of the steel plate can take place at the interface between the steel and the adhesive. The existence of chlorides in the corrosion product was also detected. Similar results were observed for a small section of plate removed from a strengthened highway bridge. A microstructural analysis of the concrete/resin system using marker solutions and electron microscopy revealed cracks and pores in the concrete and the resin. These cracks were shown to act as routes for corrosive liquids to reach the steel plate and cause corrosion. The use of a chromate primer on the steel plate was successful in inhibiting the corrosion without greatly affecting the structural strength.