Global bond behavior of enamel-coated rebar in concrete beams with spliced reinforcement

This paper presents an experimental study of vitreous enamel coating effects on the bond strength between deformed rebar and normal strength concrete. A total of 24 beam splice beam specimens were tested under 4-point loading with four parameters investigated: rebar size, lap splice length, coating and confinement conditions. As the splice length increases, the ratio of bond strength between coated rebar and black rebar was found to increase from 1.0 to a maximum value of 1.44 and decrease to 1.0. The maximum bond strength ratio corresponds to a splice length over rebar diameter ratio of 20–35 when the maximum elastic stress is developed in enamel-coated rebar. For a splice length over rebar diameter ratio of less than 20, an average of 10% bond strength increase was observed due to confinement provided by transverse stirrups.The concrete beams reinforced with enamel-coated rebar have a greater number of smaller flexural cracks than those containing black rebar since the enamel coated rebar can more effectively receives stress from the concrete.

► Enamel coating increases the bond strength of spliced rebar in concrete up to 44%.
► Confinement increases the bond strength of short-spliced, coated rebar by approximately 10%.
► Enamel coating increases the ultimate load of spliced beams with little change in stiffness.
► Beams with enamel coated rebar have more fine flexural cracks than those with black rebar.
► The critical splice length of enamel-coated rebar ranges from 35 to 43 times the rebar diameter.