*Corresponding Author: saadisasarsam@coeng.uobaghdad.edu.iq (Saad I. Sarsam ORCID 0000-0001-8426-5767) Received 28 March 2020 Revised 18 Apr 2020 Accepted 20 Apr 2020 Civil Enginering Beyond Limits 3 (2020) 8-14 2687-5756 © 2019 ACA Publishing. All rights reserved. https://doi.org/10.36937/cebel.2020.003.002 8 Civil Engineering Beyond Limits 3 (2020) 8-14 Civil Engineering Beyond Limits www.acapublishing.com Research Article Influence of Surface Texture on Interface Bond Shear Strength of Asphalt Concrete Saad Issa Sarsam, Samah Abdulrazzaq AL Nuaimi Department of Civil Engineering, College of Engineering, University of Baghdad, Iraq Abstract The bonding strength provided by the tack coat between asphalt concrete layers at the interface is considered as an essential issue in the performance of the flexible pavement throughout its service life. However, the surface texture of the pavement surface exhibits another essential issue in the bond strength. In this investigation, three layers of asphalt concrete (base, binder and wearing) courses with (25, 19, and 12.5) mm of nominal maximum size of aggregates have been prepared using roller compactor. Rapid curing cutback RC-70 and cationic medium setting emulsion CMS have been implemented as tack coats with three application rates. The slab specimens were subjected to mean texture depth determination using sand patch method. Core specimens of 102 mm diameter were obtained from the prepared slab samples and subjected to interface bond strength test with the aid of a special manufactured mold. Test results were analyzed and compared. It was concluded that when RC- 70 tack coat was implemented, asphalt concrete binder course laid on base course exhibited the highest shear strength of 1600 kPa at an application rate of 0.33 liter/m2 when compared to other application rates. Asphalt concrete wearing course laid on binder course exhibited the highest shear strength of 1515 kPa at an application rate of 0.15 liter/m2 when compared to other application rates. When CMS tack coat was implemented, asphalt concrete binder course laid on base course exhibited the highest shear strength of 1620 kPa at an application rate of 0.23 liter/m2 when compared to other application rates. Finally, the asphalt concrete wearing course laid on binder course exhibited the highest shear strength of 2272 kPa at an application rate of 0.23 liter/m2 when compared to other application rates. Keywords: Cutback, Emulsion, Tack coat, Asphalt concrete, Interface bond, Texture 1.Introduction The Flexible pavement consists of interconnected layers of asphalt concrete mixtures. Bonding between the layers is an essential parameter in the long-term serviceability of the pavement. The interface bonding of layers is subjected to dynamic loading coming from wheel load repetitions as reported by Szydlo and Malicki,[1]. An attempt has been made by Panda et al.,[2] to develop a simple testing arrangement to be used in the laboratory to determine the interlayer bond shear strength. It was stated that the boundary between the consecutive asphaltic layers is the layer interface while the pavement stress distribution is highly influenced by the adhesion conditions at this interface. Poor adhesion between pavement layers causes adverse effects on the structural strength of the pavement system. Slippage and delamination failures could occur, thus defeating the safety and construction objectives. It is concluded that Cationic rapid setting (CRS-1) emulsion applied at 0.25 Kg/m 2 offers the best results of interlayer bond strength. Ghaly et al.,[3] evaluated the practice followed of using tack coat through controlled laboratory simple shear tests and determined the optimum tack coat application rate. The influences of tack coat types, application rates, viscosity and temperatures on the interface shear strength were assessed. It was concluded that modified asphalt emulsion has the highest interface bond strength. It was also found that applying low viscosity tack coat emulsion at two layers is more effective than a tack coat emulsion with high viscosity one-layer coat. Andrea and Tozzo,[4] analyzed the shear behavior of double-layer specimens with the same features tested in different state of stress but at the same deformation rate. The tests were performed on two devices, designed to reproduce the most common stress/deformation relationship and modified to allow the comparison of the results. The maximum shear stress and the corresponding normal stress were evaluated by the tests. It was concluded that there is a relationship between these parameters and the specimens’ features. Zhang, [5] focused on how the interlayer shear strength varied when relevant influential factors are changed. Results indicate that the interlayer shear strength increased with the decreased test temperature, increased traffic load, and increased test confinement pressure. Chen and Huang, [6] evaluated the interlayer shear strength by different gradation combinations. The direct shear test was used to measure the bond properties provided by tack coat,