Airfield and Highway Pavements 2019 164 © ASCE Cracking Resistance of Sulfur Extended Asphalt Mixtures Using Illinois Flexibility Index Test Uthman Mohammed-Ali 1 ; Jose J. Rivera-Perez 2 ; Hasan Ozer 3 ; and Imad L. Al-Qadi 4 1 Graduate Research Assistant, Illinois Center for Transportation, Dept. of Civil and Environmental Engineering, Univ. of Illinois at Urbana–Champaign, 205 North Mathews, Urbana, IL 6180. E-mail: uthmanm2@illinois.edu 2 Graduate Research Assistant, Illinois Center for Transportation, Dept. of Civil and Environmental Engineering, Univ. of Illinois at Urbana–Champaign, 205 North Mathews, Urbana, IL 6180. E-mail: riverap2@illinois.edu 3 Research Assistant Professor, Illinois Center for Transportation, Dept. of Civil and Environmental Engineering, Univ. of Illinois at Urbana–Champaign, 205 North Mathews, Urbana, IL 6180. E-mail: hozer2@illinois.edu 4 Bliss Professor of Engineering, Illinois Center for Transportation, Dept. of Civil and Environmental Engineering, Univ. of Illinois at Urbana–Champaign, 205 North Mathews, Urbana, IL 6180. E-mail: alqadi@illinois.edu ABSTRACT Sulfur is an abundant co-product of the oil and gas production. By 2020, new regulations limiting the sulfur content in maritime fuels will increase its supply. There is a need to revisit cracking characteristics of sulfur modified asphalt concrete (AC) mixtures. The objective of this study is to evaluate the cracking resistance of sulfur extended asphalt (SEA) mixtures as compared to AC prepared with standard binders. One conventional AC and two SEA mixtures were prepared in the laboratory containing 0%, 15%, and 30% sulfur replacement by weight of the binder, respectively. The sulfur was added during the mix production in the form of pellets to mimic the procedures that can be used during plant production. The Illinois flexibility index test was used to assess the cracking susceptibility of SEA mixtures. Results obtained indicate decreasing cracking resistance with increase in sulfur addition. Keywords: sulfur, asphalt, binder, mixture, performance tests, fracture mechanics, temperature cracking INTRODUCTION Background During 1970, the United States oil crisis resulted in a shortage of asphalt binder. At the same time, there was an increasing supply of sulfur from the fossil fuel industry. In the wake of the crisis, the Federal Highway Administration (FHWA) developed guidelines for the design, construction and evaluation of Sulfur-Extended Asphalt (SEA) mixtures that replace the binder by elemental sulfur. Interest in the use of SEA has re-emerged following new regulations from the International Maritime Organization (IMO) that reduce the allowed concentration of sulfur in maritime fuels from 3.5% to just 0.5% by 2020 (George & Ghaddar, 2018). As a result, petroleum exporting regions such as Saudi Arabia are considering the use of SEA to address the expected sulfur surplus. SEA mixtures use elemental sulfur as a binder extender. The sulfur/binder mass ratios in SEA can range from 20/80 up to 40/60. Approximately, 20% of the sulfur mass dissolves in the Airfield and Highway Pavements 2019 Downloaded from ascelibrary.org by University of Illinois At Urbana on 10/13/19. Copyright ASCE. For personal use only; all rights reserved.