Effect of using carbon nanotube modified epoxy on bond–slip behavior between concrete and FRP sheets Mohammad R. Irshidat a,⇑ , Mohammed H. Al-Saleh b a Department of Civil Engineering, Jordan University of Science and Technology, Irbid, Jordan b Department of Chemical Engineering, Jordan University of Science and Technology, Irbid, Jordan highlights  Bond–slip behavior between concrete and FRP composites was improved using CNT.  Using CNT modified epoxy enhanced both bond strength and ultimate slippage.  Bond enhancement between FRP and concrete depends on fiber and epoxy type and bond area.  SEM images showed that CNTs could improve the adhesion at the FRP/concrete interface. graphical abstract article info Article history: Received 7 September 2015 Received in revised form 22 December 2015 Accepted 23 December 2015 Keywords: Carbon nanotubes FRP Bond Interface Concrete abstract The influence of carbon nanotubes (CNTs) on the bond–slip behavior between concrete surfaces and fiber-reinforced polymer (FRP) sheets was investigated. A total of 30 concrete prisms were casted, rein- forced with FRP sheets, and tested under double-shear test. Carbon or glass FRP sheet strips with different lengths and widths were externally bonded to the concrete prisms using either neat or CNT modified epoxy. The effects of epoxy type, fiber sheet type, FRP bond length, and FRP bond width on the bond behavior were investigated through the failure mode, bond stress versus slip curves, and scanning elec- tron microscopy (SEM) imaging. Experimental results showed that using CNT modified epoxy resin enhanced the bond strength and ultimate slippage of the tested specimens. The enhancement was highly dependent on the type of epoxy and fiber sheet. The bond behavior between concrete surface and FRP was affected by bond length and width. Scanning electron microscope images showed that CNTs could improve the adhesion at the carbon fiber/epoxy interface and concrete/epoxy interface leading to improvement in the load transfer and bond strength. Ó 2015 Elsevier Ltd. All rights reserved. 1. Introduction Recently, fiber-reinforced polymer (FRP) has been widely used in strengthening of concrete structures due to several reasons such as high strength to weight ratio, high corrosion resistance, and ease http://dx.doi.org/10.1016/j.conbuildmat.2015.12.183 0950-0618/Ó 2015 Elsevier Ltd. All rights reserved. ⇑ Corresponding author at: Department of Civil Engineering, Jordan University of Science and Technology, P.O. Box 3030, Irbid 22110, Jordan. E-mail address: mrirshidat@just.edu.jo (M.R. Irshidat). Construction and Building Materials 105 (2016) 511–518 Contents lists available at ScienceDirect Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat