Local bond strength of vitreous enamel coated rebar to concrete

In this paper, the bond strength between vitreous enamel coated rebar and concrete is characterized through testing of 96 pullout cylinder specimens. Key parameters investigated include rebar diameter, coating condition, confinement condition, concrete cover-to-rebar diameter ratio, and concrete strength. The unconfined and confined cylinders fail in concrete splitting with crushing zones distributed at rib fronts and concrete splitting plus shearing off, respectively. The enamel coating reduces the crushing angle and increases the crushing length of concrete. Within the test ranges of various parameters, the overall increase in bond strength of the enamel coated rebar in normal concrete is approximately 15%. Confinement or reduction of rebar size can increase the effect of enamel coating on the bond strength by 2–4%.

► Enamel coating increases the bond strength of deformed rebar in concrete by approximately 15%.
► Enamel coating roughens rebar surface and increases the chemical adhesion of rebar in concrete.
► Confinement slightly increases the bond strength of enamel coated rebar in concrete.
► Increasing rebar size increases bearing effect on concrete and reduces frictional and chemical effects.
► Enamel coated rebar is pulled out of concrete cylinders with smaller concrete crushing angles.