Effects of liquid antistrip additives on rheology and moisture susceptibility of water bearing warm mixtures Feipeng Xiao a, * , Serji N. Amirkhanian b a Asphalt Rubber Technology Service (ARTS), Department of Civil Engineering, Clemson University, Clemson, SC 29634-0911, USA b Department of Civil Engineering, Clemson University, Clemson, SC 29634-0911, USA article info Article history: Received 20 October 2009 Received in revised form 7 February 2010 Accepted 11 February 2010 Available online 21 March 2010 Keywords: Viscosity Complex modulus Warm mix asphalt Anti-stripping additive Creep recovery Creep compliance Indirect tensile strength abstract Warm mix asphalt (WMA) has been gaining increasing popularity in recent years around the world. Ris- ing energy prices, global warming, and more stringent environmental regulations have resulted in an interest in WMA technologies as a mean to decrease the energy consumption and emissions. However, the water absorption and release process caused by water bearing WMA additive (Asphamin) makes the charge re-distribution complex and thus may result in the moisture induced damage of asphalt mix- tures. Especially, the liquid antistrip additives (ASAs) blended with the binder and then mixed with aggregate and Asphamin make the issue more complicated. The objective of this study was to investigate and evaluate the rheological properties and moisture susceptibility of the binder and mixture containing ASAs and Asphamin additive. The experimental design for this study included rheological property tests of binders and moisture susceptibility of mixtures. The materials included one binder (PG 64-16), two liquid ASAs and hydrated lime, one water bearing additive, and three aggregate sources. The performed testing included viscosity, performance grade, creep and creep recovery, amplitude sweep, frequency sweep, boiling test, and indirect tensile strength (ITS). The results indicated that the addition of Asphamin can slightly increase the viscosity, failure temperature and G Ã /sin d values. The mixture containing Asph- amin has a lower ITS value than others. Statistical analysis illustrates that there is not significant differ- ence in ITS value between any mixtures containing Asphamin additive and control mixtures. However, significant differences can be found between mixtures containing Asphamin and without any Asphamin additive. Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction In recent years, the asphalt industry has investigated the warm asphalt technology as a mean to reduce the mixing and compaction temperatures of asphalt mixes. Warm mix asphalt (WMA) is an as- phalt mixture which is mixed at temperatures lower than conven- tional hot mix asphalt. Typically, the mixing temperatures of warm mix asphalt range from 100 to 140 °C (212–280 F) compared to the mixing temperatures of 150–180 °C (300–350 F) for a typical hot mix asphalt [1–4]. Thus, warm asphalt has been gaining increasing popularity in recent years around the world. Rising en- ergy prices, global warming, and more stringent environmental regulations have resulted in an interest in warm mix asphalt technologies as a mean to decrease the energy consumption and emissions associated with conventional hot mix asphalt produc- tion [3–8]. European countries are already using warm asphalt technologies that allow reducing 28–56 °C (50–100 °F) in mixing and compaction temperatures. However, since the environmental conditions, equipment, standards, work practices, among many other factors, are different in the United States, a thorough investi- gation of warm asphalt is necessary before it is implemented in the United States. The ‘World of Asphalt’ in 2004 featured a demon- stration project on warm mix asphalt, and since then, the major warm asphalt additive companies have carried out several other demonstration projects in the United States [3,4]. The interim re- port of NCHRP 9-47 completed by Anderson et al. [9] indicated that generally WMA technologies can be separated into four categories (organic additives, chemical additives, water-bearing additives, and water-based processes). The phenomenon of breaking the bond between the aggregate and the binder is known as stripping. A typical situation is the gradual loss of strength over the years, which causes many surface manifestations like rutting, corrugations, shoving, raveling, crack- ing, etc. [10,11]. To prevent moisture susceptibility, proper mix de- sign is essential. Of the many ways to prevent stripping in a pavement, the use of anti-stripping agents (ASAs) is the most com- mon method [12–16]. One of the most commonly used ASAs in the United States is hydrated lime. Others include liquid ASAs such as 0950-0618/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.conbuildmat.2010.02.027 * Corresponding author. Tel.: +1 864 6566799; fax: +1 864 6566186. E-mail addresses: feipenx@clemson.edu (F. Xiao), kcdoc@clemson.edu (S.N. Amirkhanian). Construction and Building Materials 24 (2010) 1649–1655 Contents lists available at ScienceDirect Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat