Yonghong Ruan, Richard R. Davison, and Charles J. Glover

Texas A&M University, Department of Chemical Engineering, 3122 TAMU, College Station, Texas 77843-3122

Received October 1, 2002

Abstract

Asphalt binders are complex mixtures of a wide variety of hydrocarbon materials. Added to this complexity in recent years has been modification with a variety of polymer modifiers. Binders used in this study were commercial materials obtained directly from the suppliers. They include diblock poly (styrene-b-butadiene) rubber (SBR), triblock poly (styrene -butadiene-styrene) (SBS), and high-cure ground tire rubber. A study of the effect of these modifiers on oxidative aging and on changes in physical properties due to aging shows several effects. Modifiers can reduce oxidative aging rates to some degree, but a bigger effect tends to be to reduce the hardening of binders that occurs in response to oxidative aging. This reduction in hardening rate is expected to have a positive effect on pavement performance over time, relative to the performance of base asphalts. Furthermore, the effectiveness of modifiers varies with the base asphalt.

Read more, klik here for download

J. Murali Krishnan, K.R. Rajagopal

Department of Civil Engineering, Indian Institute of Technology Madras, Chennai 600 036, India. Department of Mechanical Engineering, Texas A&M University, College Station, TX 77840, USA.

Received 15 June 2004; received in revised form 29 July 2004

Abstract

Knowledge of the mechanical and thermodynamic behavior of straight run asphalt is desirable in view of its use as a binder for pavement applications. The different complex processes undergone by asphalt concrete mixtures such as healing, aging, etc. can be understood more clearly, if one has a better understanding of the constitutive behavior of asphalt. The need is pressing as the use of polymer-modified asphalt as a binder has increased in recent years. Most of the studies carried out on constitutive modeling of asphalt model pure asphalt either as a Newtonian fluid or as a linear viscoelastic fluid over a wide range of temperatures. The complexity related to the study of the constitutive behavior of asphalt is compounded by the fact that asphalt is a mixture of different chemical species some of which are amorphous and some of which are crystalline in nature. The relaxation mechanisms of asphalt are diverse with different relaxation mechanisms at different temperatures. In this study, we use a thermodynamic framework for the constitutive modeling of asphalt and we model asphalt as a material with multiple relaxation mechanisms. This framework recognizes the fact that materials like asphalt can exist in more than one natural configuration (for instance, stress free configuration). We use the experimental data available in the literature (Lethersich, W., 1942. The mechanical behaviour of bitumen. Journal of the Society of Chemical Industry 61, 101–108; Cheung, C.Y., Cebon, D., 1997. Experimental study of pute bitumens in tension, compression, and shear. Journal of Rheology 41 (1), 45–73) for asphalt from different sources and demonstrate the efficacy of the model.

Read more, klik here for download

Zhanping You, Julian Mills-Beale, Justin M. Foley, Samit Roy, Gregory M. Odegard, Qingli Dai, Shu Wei Goh

Department of Civil and Environmental Engineering, Michigan Technological University, 1400 Townsend Drive, Houghton, MI 49931-1295, United States. Department of Aerospace Engineering and Mechanics, University of Alabama, Tuscaloosa, AL 35487-0280, United States. Department of Mechanical Engineering – Engineering Mechanics, Michigan Technological University, 1400 Townsend Drive, Houghton, MI 49931-1295, United States

Abstract

The objective of this study is to review existing literature in the area of nano-modification of asphalt and proceed to apply nano-materials to asphalt to improve the performance. This study integrates literature review, preparation, and characterization of nano-modified asphalt materials. In the experimental testing montmorillonite, nanoclay at 2% and 4% by weight of asphalt was blended in asphalt binder at a high temperature to exfoliate the nanoclay within the asphalt. The asphalt binder was then characterized using the Superpave™rotational viscosity, dynamic shearmodulus, and direct tension test. The rotational viscosity results indicate that the addition of the two types of nanoclay, Nanoclay A and Nanoclay B, increased the rotational viscosity by an average of 41% and 112%, respectively, across test temperatures 80, 100, 130, 135, 150 and 175 oC. It was found that the dynamic shear complex modulus (G*) value increases significantly across a range of testing temperatures (from 13 to 70 oC) and loading frequencies (0.01–25 Hz). With 2% Nanoclay A reinforcement in the asphalt binder, the complex shear moduli generally increased by 66% while the 4% Nanoclay A reinforcement in the asphalt binder generally increased the shear complex moduli by 125%. The 2% and 4% Nanoclay B increased the shear complex moduli by 184% and 196%, respectively. In terms of direct tension strength, the use of Nanoclay A and Nanoclay B reduced the strain failure rate of the original binder while the secant or direct tension moduli showed increase with the addition of the nanoclays. In furtherance of this research, nanoclay-modified asphalt is being tested at percentages higher than 4% to underscore the fact that nanoclays may have the potential to reduce rutting and cracking.

Read more, klik here for download

Irena Gawel, Robert Stepkowski, and Franciszek Czechowski

Faculty of Chemistry, Department of Fuels Chemistry and Technology, Wroclaw UniVersity of Technology, 7/9 Gdanska Street, Wroclaw 50-344, Poland, Rubber Research Institute “Stomil”, 30 Harcerska Street, Piastow 05-820, Poland, and Institute of EnVironment Protection Engineering, Wroclaw UniVersity of Technology, 9 Grunwaldzki Pl., 50-377 Wroclaw, Poland

Abstract

The analysis of the interactions between rubber and asphalt was carried out. The swelling rate and equilibrium of rubber penetration with the selected asphalt components were found to be dependent on these components and the rubber content in asphalt. At fixed conditions of stirring asphalt with rubber, the equilibrium swell value decreases with the increase in rubber content. From the gel permeation chromatography (GPC) analysis, it follows that the lighter asphalt components penetrate more readily into the internal matrix of the polymer. The gas chromatography-mass spectrometry (GC-MS) study allowed us to assess which components penetrated from asphalt into the rubber and which moved from rubber to asphalt. It has been found that of the nonpolar components, the n-alkanes and n-alkylbenzenes, possess the highest propensity to penetrate into rubber particles. Preferential absorption of the compounds with linear aliphatic chains into the rubber suggests that these components have a good compatibility with the linear polymeric skeleton of the rubber. During immersion of the rubber in hot asphalt, the fatty acids, which are the components of the curing system of the polymer, move from rubber to asphalt, and they are most probably concentrated in the naphthene-aromatic fraction of the asphalt. The electron paramagnetic resonance (EPR) study confirmed the effect of the immersion time of rubber in asphalt and of the shear on the swelling rate.

Read more, klik here for download

Diego O. Larsen, José Luis Alessandrini, Alejandra Bosch, M. Susana Cortizo

Laboratorio de Pavimentos e Ingeniería Vial, Facultad de Ingeniería, Universidad Nacional de La Plata, 1900 La Plata, Argentina. Departamento de Física, Facultad de Ciencias Exactas y Comisión de Investigaciones Científicas de la Provincia de Buenos Aires (CIC), Universidad Nacional de La Plata, 1900 La Plata, Argentina. Centro de Investigación y Desarrollo en Fermentaciones Industriales (CINDEFI, CONICET), Facultad de Ciencias Exactas, Universidad Nacional de La Plata, 1900 La Plata, Argentina. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), Facultad de Ciencias Exactas – CONICET, Universidad Nacional de La Plata, Casilla de Correo 16, Sucursal 4, 1900 La Plata, Argentina.

Abstract

Two styrene–butadiene–styrene block (SBS) copolymers which differ in weight average molecular weight and two base asphalts (from local crude source, Argentina) had been blended under different experimental conditions. Rotational viscosity, fluorescence microscopy, size exclusion chromatography (SEC) and FT-IR spectrometry were used in order to study the rheological and morphological changes of the blends during their manufacturing. Our results show that the high shear rate and temperature used during this procedure induce the SBS copolymer degradation and the degradation fragments distribution into maltenic asphalt phase. These events are responsible for the observed changes. The optimal time which produces the best rheological properties of modified asphalt depends on the blend composition and on the shear rate used.

Read more, klik here for download

Chui-Te Chiu, Tseng-Hsing Hsu, Wan-Fa Yang

Department of Civil Engineering, Chung Hua University, Taiwan

Received 15 March 2007; received in revised form 3 July 2007; accepted 4 July 2007. Available online 21 August 2007

Abstract

This research performed life cycle inventory using proposed recycledmaterial formulas and service records and incorporating the database provided by Eco-indicator 99 in order to study the eco-burden presented by using recycled materials to rehabilitate asphalt pavements. Three recycled materials (recycled hot mix asphalt, asphalt rubber, and Glassphalt) and the traditional hot-mixed asphalt are compared. Assuming that the thickness of the asphalt is 5 cm and the service life is 6 years, the eco-
burden presented by the traditional hot-mixed asphalt is 3.45 kPt. per lane-kilometer. Using recycled hot mixed asphalt can reduce the eco-burden by 23%under the same conditions. Using asphalt rubber increases the eco-burden by 16%, while the eco-burden remains essentially the same (reduced by less than 1%) using Glassphalt. Taking into account the difference in service life between different materials, this research also uses a 40-year time span to evaluate the eco-burden for eachmaterial. The results show that the traditional hot mixed asphalt has an eco-burden of 23.03 kPt. for that time span. Both recycled hot mixed asphalt and asphalt rubber can reduce the eco-burden by 23% in the same period. On the contrary, Glassphalt increases the eco-burden by 19%. This research also identified the sources of the eco-burden for these asphalts. The results showthat a large percentage of the eco-burden comes from two sources, the asphalt binder used (39–48%) and the heat sources required to process these paving materials (42–50%). This suggests that the most effective way to lower the eco-burden may be to reduce the heat requirement during the manufacturing process.

Read more, klik here for download

Baoshan Huang, Xiang Shu, Guoqiang Li

Department of Civil and Environmental Engineering, The University of Tennessee, Knoxville, TN 37996, United States Department of Mechanical Engineering, Louisiana State University, Baton Rouge, LA 70803, United States

Received 3 May 2005; accepted 3 May 2005

Abstract

Recycled asphalt pavement (RAP) is the removed and/or reprocessed pavement material containing asphalt and aggregate. The use of RAP in asphalt pavement has become a common practice in the construction of new, and reconstruction of old, hot mix asphalt (HMA) pavements. But little research has been done to examine the potential of incorporating RAP into concrete. Since RAP contains asphalt, it is very likely that the toughness of concrete made with RAP could be improved. In the present study, the mechanical properties of RAP-incorporated Portland cement concrete were investigated through laboratory experiments. Two types of RAP (coarse and fine RAP) materials were considered. The results from this study indicated that RAP could be incorporated into Portland cement concrete without any modification to the conventional equipment or procedures. Without any treatment, there was a systematic reduction in the compressive and split tensile strengths with the incorporation RAP in concrete. Notably, the energy absorbing toughness for the RAP incorporated concrete has been significantly improved.

Read more, klik here for download

Jianying Yu, Peiliang Cong, Shaopeng Wu

Key Laboratory of Silicate Materials Science and Engineering of Ministry of Education, Wuhan University of Technology, Wuhan 430070, China

Abstract

The flame retardancy of asphalt binder was improved by adding flame retardants in previous research. The research was conducted to assess the performance of two kinds of flame resistant asphalt mixture compared with the control mixture in laboratory. Differential scanning calorimetry (DSC) and thermo-gravimetry (TG) were employed to investigate the effect of aluminium hydroxide (ATH) on the thermal properties of asphalt binder. The mixture was designed using Superpave (Superior Performing Pavement) methods and related pavement performance was evaluated. The wheel-tracking was employed to research the dynamic plastic deformation performance. Experimental results illustrated that two kinds of flame resistant asphalt binders have better flame retardancy and all the pavement performances of two kinds of modified asphalt mixture can meet the Superpave design requirements. Therefore, it was feasible to prepare asphalt mixture with the excellent flame retardancy and pavement performance using ATH modified asphalt binders.

Read more, klik here for download

Sureyya Tayfur, Halit Ozen, Atakan Aksoy

ISFALT Asphalt Company, Istanbul, Turkey. Department of Civil Engineering, Yıldız Technical University, Istanbul, Turkey. Department of Civil Engineering, Karadeniz Technical University, Trabzon, Turkey.

Received 29 July 2004; received in revised form 11 August 2005; accepted 12 August 2005. Available online 28 November 2005

Abstract

The purpose of this study is to evaluate mechanical properties of control and modified asphalt mixtures. Conventional and five modified asphalt mixtures were studied on hot mix asphalt permanent deformation resistance. Amorphous polyalphaolefin, cellulose fiber, polyolefin, bituminous cellulose fiber and styrene butadiene styrene were used as modifiers. Indirect tensile strength, indirect tensile, static and repeated creep and LCPC wheel tracking tests were used for different loading conditions and temperatures. Research was focused on comparing the interaction between LCPC wheel tracking and other mechanical tests. According to the LCPC wheel tracking and repeated creep test results SBS mixtures were found as the most resistance mixtures in view of the rutting. Additives performed different performance levels but showed more resistance to permanent deformation according to the conventional mixtures. As far as the static creep test results are concerned there are controversial results because conventional mixtures are better. It is thought that this result may stem from the static behavior of the load and rheological change of bitumen with modifiers.

Read more, klik here for download

Kyu-Dong Jeong, Soon-Jae Lee, Serji N. Amirkhanian, Kwang W. Kimd

Korea Institute of Construction Technology, 2311, Daehwa-dong, Ilsanseo-gu, Goyang-si, Gyeonggi-do 411-712, South Korea. Department of Engineering Technology, Texas State University, San Marcos, TX 78666, United States. Department of Civil Engineering, Clemson University, Clemson, SC 29634, United States. Regional Infrastructures Engineering, Kangwon National University, Chuncheon 200-701, South Korea

Abstract

The application of crumb rubber in asphalt mixtures is intended to improve the binder properties by reducing the binder’s inherent temperature susceptibility. This research investigated the interaction effects of CRM binders as a function of various blending treatments in the laboratory. For this study, CRM binders were produced using seven blending times (5, 30, 60, 90, 120, 240, and 480 min), three blending temperatures (177, 200, and 223 oC), and four rubber contents (5%, 10%, 15%, and 20% by weight of asphalt binder). The results from this study showed that (1) The interaction time and interaction temperature for CRM binders were observed to have significant effect on the binder properties; (2) The longer time and higher temperature for interaction of CRM binders resulted in an increase in the high failure temperature and the viscosity. This is thought to be due to the increase in the rubbermass through binder absorption. However, this study found that the control binder of PG 64-22 had little change of the binder properties as a function of interaction conditions; (3) The CRM percentage influence is statistically significant on the viscosity and G/sin d values. Also, the asphalt binder with higher CRM percentage showed a higher large molecular size (LMS) value, and the increase in CRM percentage is considered to result in the additional loss of the low molecular weight in the asphalt binder to the CRM.

Read more, klik here for download