Nanomaterials Applied in Asphalt Modification: A Review Changqing Fang 1)* , Ruien Yu 1,2) , Shaolong Liu 1) , Yan Li 2)* 1) College of Printing and Packing Engineering, Xi’an University of Technology, Xi’an 710048, China 2) School of Mechanical and Precision Instrument Engineering, Xi’an University of Technology, Xi’an 710048, China [Manuscript received December 28, 2012, in revised form February 28, 2013, Available online 8 April 2013] Nanotechnology has been gradually penetrated into the field of asphalt modification. Seemingly magic effects of nanomaterials have now been brought to improve the performance of asphalt. To demonstrate many of the prospective applications, researchers have conducted a series of positive and effective efforts dealing with the preparation of modified asphalt to demonstrate the mechanism of modification and the resultant improvement in performance. In this review, various nanomaterials used in asphalt modification are initially presented, followed by the methods employed to modify the asphalt with these materials and finally the effects of nanomaterials on the performance of base asphalt are presented and the modification mechanisms are discussed. Based on the current research results, the influence of preparation process parameters on the compatibility of every phase in the modified asphalt and the stability of the modified asphalt system are described. Finally, the development trend of the topic field is projected. KEY WORDS: Nanomaterials; Asphalt; Modification; Composites; Properties 1. Introduction Nanomaterials are of morphological features on the nanoscale, and especially have special properties stemming from their nanoscale dimensions [1] . Since polyamide 6/clay nanocomposite with excellent performance was prepared by Toyota research center, the polymer grade nanocomposites have attracted considerable interest in both academia and industry due to their unique mechanical, thermal, barrier, optical, electrical, and mag- netic properties [2,3] . Materials science and technology research is focused on materials at macro to micro or nanoscale. With various material states, liquid, semisolid or solid, asphalt is a black or dark complex mixture containing hydrocarbons of varying molecular weight and nonmetallic derivatives. Asphalt is usually employed as an organic binding material for waterproofing, moisture resis- tance and corrosion protection [2,4] . Modification of base asphalt is required to improve the material’ s performance (e.g. adhesion, temperature sensitivity, friction properties, oxidation resistance, aging resistance and durability). There are many kinds of asphalt modifiers, including various resins, rubbers, polymers, sulfur, metal complexes, fibers and chemical agents [4] . In recent years, nanotechnology has gradually been incorporated into the field of modified asphalt with various kinds of nanomaterials being used to modify asphalt [1] . Fig. 1 illustrates the length scales evolution of an asphalt concrete material, from macro scale to meso, micro, nano and quantum scales [5] . The microstructure is the sole determinant of macro properties, thus nano-modified asphalt of- fers a significant improvement over the fundamental material properties, which is superior to other asphalt modification methods. In August 2006, a National Science Foundation (NSF) workshop entitled Nanomodification of Cementitious Materials was held in the USA, which focused on using nanotechnology for improvement of asphalt concrete. One of the main conclusions of this workshop was that nanoscience and nanotechnology could lead to improvements in asphalt pavement technology. In this workshop the field of “asphalt nano-material science” was established [5,6] . In this review, various preparation methods of nano-modified asphalts are analyzed, and the influence of nano- materials on the base asphalt’ s properties and the mechanisms are summarized. 2. Various Nanomaterials Used in Asphalt Modification Various polymer modifiers impart different inherent charac- teristics to composites. Through research and development, several good asphalt modifiers such as: polyethylene (PE), ethylene vinyl acetate (EVA), rubber and styrene butadiene styrene (SBS) block copolymer, have been identified. The lightweight, porous SBS has both the elastic properties of a rubber and the thermoplastic properties of a resin, which allows for a wide range of applications. However, some resins (such as * Corresponding author. Prof., Ph.D.; Tel.: þ86 29 82312038; Fax: þ86 29 83212512; E-mail addresses: fcqxaut@163.com (C. Fang), jxxy-ly@ xaut.edu.cn (Y. Li). 1005-0302/$ e see front matter Copyright Ó 2013, The editorial office of Journal of Materials Science & Technology. Published by Elsevier Limited. All rights reserved. http://dx.doi.org/10.1016/j.jmst.2013.04.008 Available online at SciVerse ScienceDirect J. Mater. Sci. Technol., 2013, 29(7), 589e594