Nanomechanical and chemical characterization of the interface between concrete, glass–ceramic bonding enamel and reinforcing steel

A glass–ceramic coating made by fusing dicalcium silicate and tricalcium silicate to the surface of glass-enameled steel has been successfully used to increase the bond between reinforcing steel and concrete and provide corrosion protection for the steel. A very strong interface that consists of hydrated cement and enameled glass over the top of a second strong interface between the enameled glass and the surface of the steel results from the outer layer of water-reactive silicates hydrating on contact with fresh concrete. Currently the mechanical characteristics (hardness, elastic modulus and strain-rate sensitivity), micromorphology, and the variation in interface chemical composition are being examined. Preliminary results indicate that the more gradual transition between the mechanical properties of the steel and the paste combined with improved integration between the coating and cement hydration products in the paste results in the increased bond strength observed in macroscale tests. Results from this study to characterize the developed coating are being used to engineer new optimized enamels for this unique application.

► Coating developed to increase bonding and corrosion resistance of steel for concrete.
► Microstructural characterization and nanoindentation measurements performed on ITZ.
► Properties of ITZ transform over longer length scale of coated vs. uncoated steel.
► Gradual transition of properties between steel/paste suggest resistance to debonding.
► Improvements in bond strength correlate to pullout tests.