Posted By Ahmad Hafizullah on February 19, 2011
Improved Properties of Polystyrene-Modified Asphalt Through Dynamic Vulcanization
Hailong Jin, Guangtao Gao, Yong Zhang, Yinxi Zhang, Kang Sun, Yongzhong Fan
Polymeric Materials Research Institute, Shanghai Jiao Tong University, Shanghai 200240, People’s Republic of China. State Key Lab of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai 200030, People’s Republic of China.
Received 27 September 2001; accepted 7 November 2001
Abstract
Storage-stable polystyrene (PS)-modified asphalt has been successfully prepared in the presence of linear styrene–butadiene–styrene triblock copolymer (SBS) through dynamic vulcanization. The vulcanization characteristics of the asphalt/PS/SBS/sulfur blends were studied using a strain-controlled rheometer. At temperatures from 140 to 180°C, the curing rate of the blends increases significantly with increasing temperature. A suitable processing temperature is between 170 and 180°C for the sake of good mechanical and thermal stability properties. The physical properties, including softening point, penetration, and ductility at low temperature of the modified asphalt through dynamic vulcanization were compared to that of modified asphalt without sulfur. The storage stability of the PS-modified asphalt was effectively improved in the presence of SBS through dynamic vulcanization. The morphology and rheological properties of the modified asphalt were also investigated using an optical microscope and a dynamic shear rheometer, respectively. The morphology was compared between the pure PS-modified asphalt, the PS/SBS-modified asphalt, and the PS/SBS/sulfur-modified asphalt, which indicated that the compatibility and high-temperature storage stability of the PS-modified asphalt were improved significantly in the presence of SBS through dynamic vulcanization.
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Posted By Ahmad Hafizullah on February 19, 2011
Fiber-Reinforced Asphalt-Concrete – A Review
Sayyed Mahdi Abtahi, Mohammad Sheikhzadeh, Sayyed Mahdi Hejazi
Department of Civil Engineering, Isfahan University of Technology, Isfahan 84156-83111, Iran. Department of Textile Engineering, Isfahan University of Technology, Isfahan 84156-83111, Iran
Abstract
Asphalt concrete (AC), a mixture of bitumen and aggregates, is a sensitive material compared to other configurations used in civil engineering. Therefore scientists and engineers are constantly trying to improve the performance of asphalt pavements. Modification of the asphalt binder is one approach taken to improve pavement performance. Nowadays, there are different materials that have been employed to reinforce asphalt concrete. Furthermore, fibers and polymers are two important examples used for this purpose. However, it has been claimed that among various modifiers for asphalt, fibers have gotten much attention for their improving effects. Different researchers reported the results of the addition of a large variety of fibers to asphalt concrete as fiber-reinforced asphalt-concrete (FRAC). Basically, fiber reinforcement is considered as a coin with two sides. One side includes the randomly direct inclusion of fibers into the matrix, i.e. asphalt concrete and/or Portland Cement Concrete slabs. Another side comprises oriented fibrous materials, e.g. Geo-synthetics family. It is emphasized that the former concept is not as well-known as the second. As a result, this paper is going to focus on the first side of the coin and to investigate FRAC materials modified by random fiber inclusion. Also, the effect of different fibers, mixing procedures and executive problems on asphalt concrete will be inspected. In this way, different literature reviews illustrated that the use of fibers in AC material has been involved with three dissimilar targets: mechanical improvement, preparation of electrically conductive mixtures, and creation of a new market to manage the waste fibers.
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Posted By Ahmad Hafizullah on February 19, 2011
Feasibility Study of Asphalt-Modified Mortars Using Asphalt Emulsion
Hun Song, Jeongyun Do, Yangseob Soh
Research Center of Industrial Technology, Chonbuk National University, Chonju 561-756, South Korea. Faculty of Architecture and Urban Engineering, College of Engineering, Chonbuk National University, South Korea
Received 9 September 2004; received in revised form 9 September 2004; accepted 31 January 2005. Available online 7 April 2005
Abstract
Asphalt emulsion is manufactured by emulsification of asphalt, and it is an energy-saving, ecologically safe material because it does not need any heating processes creating gas emission and fire hazard in its use. The purpose of this study is to evaluate the feasibility on the use of an asphalt emulsion as a polymeric admixture. Asphalt-modified mortars using an experimentally manufactured asphalt emulsion are prepared with various polymer–cement ratios, and tested for strengths, adhesion, water absorption,
water permeation, carbonation and chloride ion penetration. As a result, it is found that waterproofness, carbonation resistance and chloride-ion penetration resistance of the asphalt-modified mortars are markedly improved with the increase in the polymer–cement ratio, while their compressive strength and adhesion to mortar substrates are reduced with the increase in polymer–cement ratio. Therefore, it is recommended to control their polymer–cement ratios to be less than 10% in practical applications. Further study to improve their compressive strength and adhesion is suggested.
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Posted By Ahmad Hafizullah on February 19, 2011
Experimental Study of Fibers In Stabilizing and Reinforcing Asphalt Binder
Huaxin Chen, Qinwu Xu
School of Materials Science and Engineering, Chang’an University, Xi’an 710064, China. Civil, Architectural and Environmental Engineering, University of Texas at Austin, TX 78712, USA
Abstract
This investigation examines fibers’ physical properties, reinforcing effects and mechanisms for stabilizing and reinforcing asphalt binder. Laboratory tests of water absorption, mesh-basket draindown, and oven heating were designed and performed on five fiber types (two polyesters, one polyacrylonitrile, one lignin and one asbestos), to evaluate their wettability, asphalt absorption and stabilization, and thermostability, respectively. The cone sink experiment was designed to study fiber modified asphalt’s resistance to flow, and the standard dynamic shear rheometer test was conducted to evaluate fiber modified asphalt’s rheological properties and rutting resistance. Fibers’ microstructures and spatial network formed in asphalt binder were observed using Scanning Electron Microscopy (SEM). Results indicate that fibers can effectively improve asphalt binder’s resistance to rutting and flow, and dynamic shear modulus. Fiber reinforces asphalt matrix through its functions of spatial networking, adhesion and stabilization of asphalt binder. Polyester and polyacrylonitrile fibers seem to have greater network effect than the lignin and asbestos fibers, and their antenna features at fibers’ ends further strengthens this effect. The lignin fiber
has the highest water absorption while lowest thermostability. The lignin and asbestos fibers pose greater effects of asphalt absorption and stabilization than do polymer fibers.
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Posted By Ahmad Hafizullah on February 19, 2011
Evaluation of Potential Processes for Use in Warm Mix Asphalt
Graham C. Hurley1 and Brian D. Prowell
Abstract
Several new processes have been developed to reduce the mixing and compaction temperatures of hot mix asphalt without sacrificing the quality of the resulting pavement. Three potential warm mix asphalt processes were evaluated in this study. They were Aspha-min®, Sasobit®, and Evotherm®. A laboratory study was conducted to determine the applicability of these processes to typical paving operations and environmental conditions commonly found in the United States, including the performance of the mixes in quick traffic turn-over situations and high temperature conditions.
All three processes were shown to improve the compactability of mixtures in both the SGC and vibratory compactor. Statistics indicated an overall reduction in air voids. Improved compaction was noted at temperatures as low as 190°F (88°C). Superpave gyratory compactor results indicated that Aspha-min®, Sasobit®, and Evotherm® may lower the optimum asphalt content. The addition of Aspha-min®, Sasobit®, or Evotherm® did not affect the resilient modulus of an asphalt mix nor did they increase the rutting potential of an asphalt mix as measured by the Asphalt Pavement Analyzer. The rutting potential did increase with decreasing mixing and compaction temperatures, which may be related to the decreased aging of the binder resulting from the lower temperatures. There was no evidence of differing strength gain with time for the mixes containing the three processes as compared to the control mixes indicating that a prolonged cure time before opening to traffic is not an issue. The lower compaction temperature used when producing warm asphalt may increase the potential for moisture damage. Overall, Asphamin®, Sasobit®, and Evotherm® appear to be viable tools for reducing mixing and compaction temperatures that can be readily added to hot mix asphalt. Reductions in mixing and compaction temperatures are expected to reduce fuel costs, reduce emissions, widen the winter paving window and facilitate niche applications such as airport runway construction where rapid open to traffic is essential.
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Posted By Ahmad Hafizullah on February 19, 2011
Evaluating Permanent Deformation In Asphalt Rubber Mixtures
Liseane P.T.L. Fontes, Glicério Trichês, Jorge C. Pais, Paulo A.A. Pereira
University Federal of Santa Catarina, Department of Civil Engineering, Rua João Pio Duarte, 88040-970 Florianópolis, Santa Catarina, Brazil University of Minho, Department of Civil Engineering, Campus of Azurém, 4800-058 Guimarães, Portugal
Abstract
Permanent deformation or rutting, one of the most important distresses in flexible pavements, has long been a problem in asphalt mixtures, mainly in countries with high temperatures such as Brazil. Through-out the years, researchers have used different test methods to estimate the rutting performance of asphalt mixtures. One of the alternatives to reduce permanent deformation in asphalt pavement layers is through the use of mixtures produced with asphalt rubber. Crumb rubber from waste tires introduced into the asphalt is one of suitable application to dispose the tires and used as an additive to enhance the properties of the conventional asphalts. This work aims at comparing the rutting performance of asphalt rubber mixtures (with dense and gap-graded aggregate gradation) with the conventional dense graded mixture most used in Brazil. The asphalt rubber mixtures were produced by the wet process using continuous blend and terminal blend asphalt rubber. To study their performance, two laboratory tests, the Repeated Simple Shear Test at Constant Height (RSST-CH) and the Accelerated Pavement Testing Simulator Test (wheel tracking) were carried out. The testing results confirmed that the use of asphalt rubber binder improves significantly the resistance to rutting. The highest resistance is presented by the mixtures produced with continuous blend binders and gapgraded aggregate gradation. The results of both testing apparatus can be correlated by a linear relationship. The testing results allowed concluding that the characteristics of the asphalt rubber binders cannot be used to predict the permanent deformation resistance of the asphalt rubber mixtures.
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Posted By Ahmad Hafizullah on February 19, 2011
Effects of Various Additives On the Moisture Damage Sensitivity of
Asphalt Mixtures
Atakan Aksoy a, Kurtulus Samlioglu,Sureyya Tayfur, Halit Ozen
Department of Civil Engineering, Karadeniz Technical University, Trabzon, Turkey. General Directorate of Highways, Ankara, Turkey. ISFALT Asphalt Company, Istanbul, Turkey. Department of Civil Engineering, Yıldız Technical University, Istanbul, Turkey
Received 15 November 2003; received in revised form 27 April 2004; accepted 5 May 2004 Available online 31 July 2004
Abstract
Effects of four additives, namely two fatty amine (Wetfix I, Lilamin VP 75P), one catalyst (Chemcrete) and a polymer (rubber), on the moisture damage of asphalt mixtures were studied. Rheological characteristics of the binders were measured using conventional methods both original and thin-film oven aged. Mechanical characteristics of the mixtures were evaluated with Marshall, indirect tensile and Lottman treatment tests. The additives used in this study reduced the level of damage due to moisture in asphalt mixtures. Minimum acceptable indirect tensile strength ratio (0.70) is achieved when Chemcrete and 0.2% of Wetfix I, and 0.4–0.6% of Lilamin VP 75P are used in asphalt mixtures. Indirect tensile strength ratio may decrease due to the relatively higher strength obtained in dry specimens with respect to the conditioned ones. Indirect tensile strength ratios of asphalt paving specimens were found to be less than the Marshall Stability ratios.
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Posted By Ahmad Hafizullah on February 19, 2011
Effects of Fibers on the Dynamic Properties of Asphalt Mixtures
WU Shaopeng, YE Qunshan, LI Ning, YUE Hongbo
Key Laboratory of Silicate Materials Science and Engineering of Ministry of Education Wuhan University of Technology, Wuhan 430070, China
Abstract
The dynamic characteristics of fber-modifed asphalt mixture were investigated. Cellulose fiber, polyester fber and mineral fber were used as additives for asphalt mixture, and the dosage was 0.3%, 0.3%, 0.4%, respectively. Dynamic modulus test using SuperPave simple performance tester (SPT) was conducted to study the dynamic modulus (E*) and phase angle (δ) for the control asphalt mixture and fber-modifed ones at various temperatures and frequencies. Experimental results show that all fber-modifed asphalt mixtures have higher dynamic modulus compared with control mixture. The dynamic modulus master curves of each type of asphalt mixtures are determined based on nonlinear least square regression in accordance with the time-temperature superposition theory at a control temperature (21.1℃). The fatigue parameter E*×sinδ and rutting parameter E*/sinδ of asphalt mixture are adopted to study the fatigue and rutting-resistance properties, and experimental results indicate that such properties can be improved by fber additives.
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Posted By Ahmad Hafizullah on February 19, 2011
Effect of Used-Tire-Derived Pyrolytic Oil Residue On the Properties of Polymer-Modified Asphalts
A.A. Yousefi, A. Ait-Kadi*, C. Roy
Department of Chemical Engineering, CERSIM, Laval University, Ste-Foy, Quebec, Canada G1K 7P4
Received 7 October 1998; received in revised form 13 August 1999
Abstract
Polymer-modified asphalts are prepared by incorporating recycled polyethylene (RPE) and a used-tire-derived pyrolytic oil residue in asphalt. A thorough characterisation showed superior properties for the modified asphalts at high temperatures. Low temperature properties of the base asphalt were found to deteriorate after addition of polymer. The asphalts modified with 10% pyrolytic oil (H18) obtained by vacuum pyrolysis of used tires showed improved low temperature properties. Based on optical micrographs it was concluded that contribution of the Ostwald ripening mechanism to phase separation of the dispersed polymer phase is negligible. It was found that the RPE structure changes in the mixture do not depend on the type of asphalt. The SHRP’s high temperature (TSHRP) criterion was found to correlate with the Ring and Ball temperature (TRB) with a systematic 208 difference between the two temperatures
TSHRP . TR&B: The asphalt mixtures containing 10% H18 and 1% polymer were found to have the best low and high temperature performance.
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Posted By Ahmad Hafizullah on February 19, 2011
Effect of Organo-Montmorillonite On Aging Properties of Asphalt
Jian-Ying Yu *, Peng-Cheng Feng, Heng-Long Zhang, Shao-Peng Wu School of Materials Science and Engineering, Wuhan University of Technology, Wuhan 430070, PR China
Abstract
Effects of organo-montmorillonite (OMMT) on thermo-oxidative and ultraviolet (UV) aging properties of asphalt were investigated. The results show that the viscosity aging index (VAI) and softening point increment (DS) of OMMT modified asphalt decrease significantly due to introduction of OMMT, and the ductility retention rate of the modified asphalt is also evidently higher than that of the pristine asphalt after thin-film oven test (TFOT) and pressure aging vessel (PAV) aging. In the meantime, both VAI and DS of the modified asphalt are obviously lower than that of the pristine asphalt after UV aging. Furthermore, compared with the pristine asphalt, the results of dynamic shear rheometer (DSR) testing exhibit smaller changes in rut factor (G*/sind) after TFOT and lower fatigue factor (G*sind) after PAV for the modified asphalt, which suggests that the effect of thermo-oxidative aging on dynamic rheological behaviors of the modified asphalt is restrained due to introduction of OMMT.
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