Improved Resistance of Long-Term Aged Warm-Mix Asphalt to Moisture Damage Containing Moist Aggregates Feipeng Xiao, Ph.D., P.E. 1 ; Veeralinga S. Punith, Ph.D. 2 ; Serji N. Amirkhanian, Ph.D. 3 ; and Carl Thodesen, Ph.D. 4 Abstract: Due to the use of many warm-mix-asphalt (WMA) additives in the market, the effect of long-term aging on these WMA mixtures is generally unclear; hence, it is necessary to simulate their performance in the laboratory. The objective of this study was to investigate the influence of various WMA additives on the moisture susceptibility of mixtures containing moist aggregates following a long-term aging process. Mass loss (percentage), indirect tensile strength (ITS) of dry and conditioned specimens, deformation (flow), and dissipated energy values were measured. The experimental design included two aggregate moisture contents (0% and approximately 0.5% by weight of the dry mass of the aggregate), two lime contents (1 and 2% lime by weight of dry aggregate), one liquid antistripping agent (ASA), five WMA additives, and two aggregate sources. A common long-term aging procedure was used in this study. The test results indicated that long-term aging improved the moisture resistance of WMA mixtures regardless of WMA additive, ASA, and moisture content. In addition, aggregate source affected the moisture resistance regardless of WMA additive, ASA, and aggregate moisture content. The effects of various WMA additives on the dissipated fracture energy of unaged mixtures are generally similar except that mixtures with Asphamin have relatively lower dry dissipated fracture energy. In addition, the aggregate type affected the dissipated energy value of WMA mixtures regardless of aging states. DOI: 10.1061/(ASCE)MT.1943-5533.0000567. © 2013 American Society of Civil Engineers. CE Database subject headings: Asphalts; Damage; Aggregates; Aging (material); Moisture. Author keywords: Warm-mix asphalt; Additive; Aging; Indirect tensile strength; Deformation; Dissipated energy. Introduction In recent times, the asphalt industry has been taking major steps and showing increasing interest in reducing energy consumption by reducing mix production temperatures, protecting the environment by reducing emissions, and conserving natural resources by using recycled materials. Warm-mix asphalt (WMA) is a technology that can facilitate achieving these objectives. WMA refers to technol- ogies and systems that allow for a substantial reduction in the pro- duction and compaction temperatures of hot-mix asphalt (HMA). In principle, the general WMA technology categories currently available in the United States for the production of asphalt mixtures at relatively low temperatures in comparison with HMA are broadly based on organic additives, chemical additives, and foaming processes (Prowell and Hurley 2007; Diefenderfer et al. 2007; D’Angelo et al. 2008). Some of the WMA technologies grouped under chemical additives include Cecabase RT, Evotherm, HyperTherm, Rediset WMX, Qualitherm, and SonneWarmix. The organic additives available on the market include Sasobit, Thiopave, and TLA-X. Organic additives provide a reduction in the binder viscosity and a lubricating effect for easier coating and mixture compaction (Tao and Mallick 2009; Xiao et al. 2010a). The original intent of using WMA was to provide better work- ability and compaction of asphalt mixtures (Wielinski et al. 2009; Middleton and Forfylow 2009). In turn, a more densely compacted asphalt pavement should also enhance its general performance. It is widely known that asphalt pavements compacted to better densities often have superior fatigue and rutting performance (Bonaquist 2009). The implementation and use of WMA may create issues as well. One of the major issues that needs to be addressed is the potential for moisture damage (Xiao et al. 2009, 2010a, b; Kvasnak and West 2009; Filippo et al. 2010; Bennert et al. 2011; Ashley et al. 2011; Shu et al. 2012). Inadequately dried ag- gregates at lower production temperatures (100–140°C), and even the possible introduction of additional moisture to the WMA from the various WMA foaming technologies, may affect the binder-to- aggregate adhesion, moisture susceptibility, and general mixture performance (Mallick et al. 2011; Mogawer et al. 2011; Xiao et al. 2011; Punith et al. 2011). The degree to which the different WMA technologies and additives affect moisture sensitivity varies and depends on many regional conditions (e.g., climate, aggregate type, and asphalt binder source) and pavement-specific conditions (e.g., traffic loading and general pavement integrity). During field production, aggregate stockpiles contain varying degrees of moisture, which depend on the general weather conditions in the area and stockpile management practices (e.g., covered or not covered, paved or unpaved underneath). During production, es- pecially in a drum plant, burner temperatures are set to dry the ag- gregate before the application of the asphalt binder. During the production of WMA, however, lower production temperatures may not thoroughly dry the aggregate, which could cause residual 1 Road Engineering Laboratory, Suzhou Univ. of Science and Technol- ogy, Suzhou, China; State Key Laboratory of Silicate Materials for Architectures, Wuhan Univ. of Technology, Wuhan 430070, China (corre- sponding author). E-mail: fpxiao@gmail.com 2 Asphalt Rubber Technology Service, Dept. of Civil Engineering, Clemson Univ., Clemson, SC 29634-0911. 3 State Key Laboratory of Silicate Materials for Architectures, Wuhan Univ. of Technology, Wuhan 430070, China. 4 Stiftelsen SINTEF, Box 4760 Sluppen, N-7465 Trondheim, Norway. Note. This manuscript was submitted on March 20, 2012; approved on July 18, 2012; published online on August 30, 2012. Discussion period open until December 1, 2013; separate discussions must be submitted for individual papers. This paper is part of the Journal of Materials in Civil Engineering, Vol. 25, No. 7, July 1, 2013. © ASCE, ISSN 0899-1561/ 2013/7-913-922/$25.00. JOURNAL OF MATERIALS IN CIVIL ENGINEERING © ASCE / JULY 2013 / 913 J. Mater. Civ. Eng. 2013.25:913-922. Downloaded from ascelibrary.org by Tongji University on 12/19/14. Copyright ASCE. For personal use only; all rights reserved.