Global bond behavior of enamel-coated rebar in concrete beams with spliced reinforcement Chenglin Wu a,1 , Genda Chen b,⇑ , Jeffery S. Volz c,2 , Richard K. Brow d,3 , Michael L. Koenigstein e,4 a Department of Civil, Architectural, and Environmental Engineering, 326 Butler-Carlton Hall, Missouri University of Science and Technology, 1401 N. Pine Street, Rolla, MO 65409-0030, United States b Department of Civil, Architectural, and Environmental Engineering, 328 Butler-Carlton Hall, Missouri University of Science and Technology, 1401 N. Pine Street, Rolla, MO 65409-0030, United States c Department of Civil, Architectural, and Environmental Engineering, 331 Butler-Carlton Hall, Missouri University of Science and Technology, 1401 N. Pine Street, Rolla, MO 65409-0030, United States d Department of Materials Science and Engineering, Missouri University of Science and Technology, 222 McNutt Hall, Rolla, MO 65409-0330, United States e Pro-Perma Engineered Coatings, 4040 Hypoint North, Rolla, MO 65401, United States highlights " 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. article info Article history: Received 6 August 2012 Received in revised form 2 October 2012 Accepted 21 November 2012 Available online 28 December 2012 Keywords: Bond strength Enamel coated rebar Normal strength concrete Beam splice abstract 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 max- imum 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. Published by Elsevier Ltd. 1. Introduction Coatings have become one of the most direct and effective ways to protect steel reinforcement from corrosion when reinforced con- crete (RC) structures are exposed to corrosive environments. Com- mercially available coating systems, such as Fusion-Bonded Epoxy (FBE), have been widely applied to protect steel rebar. However, previous studies [1–7] showed that a significant reduction of steel–concrete bond strength is induced by the FBE coating. Depending on the application condition, a coating factor of 1.2 or 1.5 was thus adopted for epoxy coated rebar in the ACI Building Code [8] and AASHTO Bridge Specifications [9]. Although this code- adopted estimated reduction in bond strength is deemed to be con- servative [3–5], an average of 15% reduction in bond strength seems reasonable [6]. The resulted increase in development length compared to black rebar not only increases the cost of materials, 0950-0618/$ - see front matter Published by Elsevier Ltd. http://dx.doi.org/10.1016/j.conbuildmat.2012.11.076 ⇑ Corresponding author. Tel.: +1 (573) 341 4462; fax: +1 (573) 341 4729. E-mail addresses: cwmqc@mst.edu (C. Wu), gchen@mst.edu (G. Chen), volzj@ mst.edu (J.S. Volz), brow@mst.edu (R.K. Brow), mkoenigstein@pro-perma.com (M.L. Koenigstein). 1 Tel.: +1 (573) 341 4479. 2 Tel.: +1 (573) 341 6280. 3 Tel.: +1 (573) 341 4401; fax: +1 (573) 341 6934. 4 Tel.: +1 (618) 920 8925; fax: +1 (573) 364 9589. Construction and Building Materials 40 (2013) 793–801 Contents lists available at SciVerse ScienceDirect Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat