Technical Paper ISSN 1996-6814 Int. J. Pavement Res. Technol. 7(6):451-455 Copyright @ Chinese Society of Pavement Engineering Vol.7 No.6 Nov. 2014 International Journal of Pavement Research and Technology 451 Introducing Combination of Nano-clay and Bio-char to Enhance Asphalt Binder’s Rheological and Aging Characteristics Renaldo Walters 1 , Ellie H. Fini 1+ , and Taher Abu-Lebdeh 1 ─────────────────────────────────────────────────────── Abstract: The life expectancy of Asphalt Binder is negatively impacted by the harsh bombardment of ultraviolet (UV) rays. UV rays cause asphalt to oxidize faster which results in deterioration of asphalt’s rheological characteristics that can lead to pavement distresses. This paper investigates merits of application of combination of nano-clay and bio-char to increase effectiveness of nano-clay to reduce asphalt oxidative aging while enhancing nan-clay dispersion. The study was conducted using one control binder (PG 64-22), two nano-clay sources and one type of bio-char, as such several modified binder blends were prepared at varying concentrations of nano-clay;the specimens were then analyzed in terms of their rheological characteristics before and after laboratory oxidation aging. The modifiers used in this study wereorgano clays (Cloisite-11 and Cloisite-15) along with bio-char, which is derived from swine manure. Rolling Thin Film Oven (RTFO) was used to age all specimens; aged and un-aged samples were then tested using a Rotational Viscometer (RV) to evaluate the changes in their rheological behavior before and after aging. Four modified blends were formulated incorporating 3% and 6% of Cloisite-11 and Cloisite-15, in presence of 3% Bio-char. Bio-char was used to improve dispersion, flow and liquidity retention, while enhancing oxidation resistance. DOI: 10.6135/ijprt.org.tw/2014.7(6).451 Key words: Asphalt; Oxidative aging; Nano-clay; Bio-char; Rheology. ─────────────────────────────────────────────────────── Introduction 12 Oxidative aging of asphalt binder has been recognized as one the main factors contributing to pavement distresses leading to reduced pavement service life. There have been many studies on developing additives to reduce asphalt aging; among those additives severalnano-particles including nano-clays have been shown to be promising additives. However, low dispersion capability of nano-clay in asphalt has been recognized as the main drawback reducing nano-clay’s effectiveness. This paper investigates merits of application of bio-char as a dispersion agent for nano-clay to decrease the rate of asphalt oxidation. This in turn, can enhance long term rheological behavior of asphalt and extend pavement service life by reducing asphalt aging susceptibility. Background There have been various attempts to modify asphalt binder in order to improve its overall performance. This includes addition of various additives such as styrene butadiene styrene (SBS), styrene butadiene rubber (SBR), ethylene glycidyl acrylate (EGA) terpolymer, crumb rubber, organo-montmorillonite, waste tire rubber, fibers and waste fibers [1]. In addition, more recently warm mix asphalt (WMA) has been attracting a lot of attention due to various advantages such as reduction in energy consumption, reduced emissions, reduced binder aging and extended construction season. Al-Rawashdeh and Sargand looked at the effects of water on 11 Department of Civil Engineering, North Carolina A&T State University, 1601 E. Market St., Greensboro, NC 27411, USA. + Corresponding Author: E-mail efini@ncat.edu Note: Submitted June 19, 2014; Revised August 10, 2014; Accepted August 21, 2014. the adhesive and cohesive strength of WMA mixtures and hot mix asphalt (HMA) mixtures [2]. The adhesion and cohesion energy of WMA mixtures was as high as those of HMA mixtures [2]. Another study looked at the anti-aging properties of asphalt binders made from different crude oils. The study focused on the impacts that aging had on saturates, aromatics, resins and asphaltenes components as well as penetration, softening point and molecular distribution [3]. Results showed that as a result of oxidation, saturates content remained the same while the aromatics and resin decreased in quantity. Aromatics and resins reacted with oxygen to develop more asphaltenes leading to a decrease in penetration and ductility. The investigation also proved that asphalt with higher activation energy and lower reaction rate coefficient has superior resistance to age performance [3]. Among more recent additives used to reduce oxidative aging is nano-clay; nano-clay has been used commonly in the adhesive and polymer industry to enhance their mechanical and physical properties such as stiffness, toughness, strength and thermal stability [4]. The primary use of nano particles as modifiers in asphalt binders has been to enhance rutting and cracking resistance [5-7]. In the asphalt industry many organic and non-organic modifiers have been used to decrease bitumen viscosity, to reduce its carbon emissions, to reduce energy consumption and to improve bitumen workability [8]. Nazzal and his teamtook a look at the fundamental characteristics of asphalt clay nano composites, which indicated that when nano-clay is added to asphalt binder, its adhesive forces are enhanced significantly while having an adverse effect on the cohesive forces [9]. It was also shown that stiffness and hardness of the asphalt binder could be improved depending on the mixing temperature and nano-clay concentration [9]. In addition, introduction of nano-clay n asphalt binder reduces binder’s temperature susceptibility and oxidative aging while