Effects of Compaction Temperature on Volumetric Properties of Rubberized Mixes Containing Warm-Mix Additives Chandra K. Akisetty 1 ; Soon-Jae Lee 2 ; and Serji N. Amirkhanian 3 Abstract: The warm-mix asphalt WMA refers to technologies that allow a significant reduction of mixing and compaction temperatures of asphalt mixes through lowering the viscosity of asphalt binders. Several studies have been carried out evaluating the properties of WMA, and it is found that warm mix additives work in different ways either in reducing the viscosity of the binder or allowing better workability of the mix at lower temperatures. In terms of rubberized asphalt mixtures, they are generally produced and compacted at higher temperatures than conventional mixtures, based on the field experience. If the technologies of warm-mix asphalt are incorporated, it is expected to reduce the mixing and compaction temperatures of rubberized asphalt mixtures to those of conventional mixtures. This study was initiated to investigate the effects of compaction temperature on rubberized mixes containing the warm mix additives. For this, four Superpave mix designs for two asphalt binders and two aggregate sources were conducted to determine optimum asphalt contents. Warm rubberized mixes were produced using two of the available processes. A total of 192 specimens 4 mix types: control mix, rubberized mix, warm rubberized mix 1, and warm rubberized mix 2  2 aggregate sources 4 compaction temperatures: 97, 116, 135, and 154°C  6 repetitions were fabricated using Superpave gyratory compactor. Volumetric properties of the specimens were evaluated. The results showed that the warm mix processes were effective to improve the volumetric properties of rubberized mixes at a certain range of compaction temperatures. DOI: 10.1061/ASCE0899-1561200921:8409 CE Database subject headings: Soil compaction; Temperature effects; Material properties; Rubber; Admixtures. Introduction Background Approximately 300 million scrap tires are generated each year in the United States Putman 2005; Shen et al. 2007. The disposal of these scrap tires has been a serious issue for many reasons e.g., lack of landfill space, environmental issues, etc.. Previous studies indicated that rubberized binders could produce asphalt pavements that would result in decreased traffic noise, reduced maintenance costs, and improved resistance to rutting and crack- ing Huang et al. 2002; Lee et al. 2008; Liang and Lee 1996; Ruth and Roque 1995; Shen et al. 2005. From these benefits, there is an increasing interest in using rubberized binders in hot-mix as- phalt HMA pavements in some states in the United States and other countries Bahia and Davies 1994; Lee et al. 2006. The warm-mix asphalt WMA refers to technologies that allow a significant reduction of mixing and compaction tempera- tures of asphalt mixes through lowering the viscosity of asphalt binders. Reduced mix production and paving temperatures would decrease the energy required to produce hot-mix asphalt, reduce emissions and odors from plants, and make better working con- ditions at the plant and the paving site Hurley and Prowell 2005a,b, 2006; Romier et al. 2006; Gandhi and Amirkhanian 2007; Kristjansdottir et al. 2007; Wasiuddin et al. 2007; Prowell et al. 2007. Rubberized asphalt mixes are generally compacted at a higher temperature than conventional mixes based on the field experi- ence Amirkhanian and Corley 2004. With lower compaction temperatures, the rubberized mixes might result in several prob- lems, such as inadequate volumetric properties e.g., high % air void and low % VFA and poor short- and long-term perfor- mance. If the technologies of warm-mix asphalt are incorporated into the mixes, optimum mixing and compaction temperatues of the rubberized mixes are expected to decrease and be comparable to those of conventional mixes. Among a number of warm-mix additives, this study evaluated two additives, Aspha-min and Sasobit. Aspha-min is sodium– aluminum–silicate that is hydrothermally crystallized as a very fine powder. It contains approximately 21% crystalline water by weight. By adding it to an asphalt mix, the fine water spray is created as all the crystalline water is released, which results in volume expansion in the binder, therefore increasing the work- ability and compactability of the mix at lower temperatures Eu- rovia Services 2008. Sasobit is a long chain of aliphatic hydrocarbons obtained from coal gasification using the Fischer– Tropsch process. After crystallization, it forms a lattice structure in the binder that is the basis of the structural stability of the binder containing Sasobit Sasol Wax 2008. More detail infor- mation regarding the two additives can be found in other reports Hurley and Prowell 2005a,b. 1 Ph.D. Graduate Student, Dept. of Civil Engineering, Clemson Univ., Clemson, SC 29634. E-mail: cakiset@clemson.edu 2 Assistant Professor, Dept. of Engineering Technology, Texas State Univ.-San Marcos, San Marcos, TX 78666 corresponding author. E-mail: soonjae93@gmail.com 3 Professor, Dept. of Civil Engineering, Clemson Univ., Clemson, SC 29634. E-mail: kcdoc@clemson.edu Note. This manuscript was submitted on March 28, 2008; approved on January 22, 2009; published online on July 15, 2009. Discussion pe- riod open until January 1, 2010; separate discussions must be submitted for individual papers. This paper is part of the Journal of Materials in Civil Engineering, Vol. 21, No. 8, August 1, 2009. ©ASCE, ISSN 0899- 1561/2009/8-409–415/$25.00. JOURNAL OF MATERIALS IN CIVIL ENGINEERING © ASCE / AUGUST 2009 / 409 J. Mater. Civ. Eng. 2009.21:409-415. Downloaded from ascelibrary.org by CLEMSON UNIVERSITY on 02/28/13. Copyright ASCE. For personal use only; all rights reserved.