Xu Yang

Bio: Xu Yang is an academic researcher from Monash University, Clayton campus. The author has contributed to research in topics: Asphalt & Asphalt concrete. The author has an hindex of 17, co-authored 55 publications receiving 893 citations. Previous affiliations of Xu Yang include Chang'an University & Monash University.

Emission analysis of recycled tire rubber modified asphalt in hot and warm mix conditions

Abstract: The hazardous emissions of crumb rubber (CR) modified asphalt during construction has been a concern for a long period. This study aims to identify the emission components in the CR modified asphalt in traditional hot mix asphalt (HMA) and with recently developed warm mix asphalt (WMA). The dynamic headspace gas chromatography-mass spectrometry (GCMS) was employed for identifying the emission of asphalt binders at 120°C, 140°C and 160°C. The coupling of gas chromatography and Fourier-transform infrared spectroscopy (GC-FTIR) was used to analyze the emission during the plant mixing for conventional HMA, CR-HMA and CR-WMA. The results showed the emission amount was highly dependent on mixing temperature. The warm mix technology can reduce the emission level significantly and should be encouraged in the asphalt mixture containing CR. Asphalt source and other extra additives in producing CR modified asphalt can also affect the emission significantly. Asphalt mixture containing CR can release toxic emissions such as xylene and toluene significantly higher compared to that without CR. In addition, it was found that the emission amount from the GCMS test for asphalt binder was lower than that in the field test for asphalt mix due to the thin asphalt film of asphalt mix.

Environmental and mechanical performance of crumb rubber modified warm mix asphalt using Evotherm

Abstract: While crumb rubber (CR) can improve the performance of asphalt pavement in several aspects, it has a noticeable concern of higher emission and increased energy consumption due to a higher production temperature. This study made a comprehensive evaluation of the environmental and mechanical performance of the CR modified warm mix asphalt with Evotherm third generation. The CR modified hot mix asphalt (HMA) and control HMA were also investigated for a comparative study. Moreover, both the laboratory compacted samples and the field collected samples were studied. The environmental performance includes the neat asphalt savings, fuel savings and hazard emission reduction. The mechanical performance evaluated included tensile strength and moisture susceptibility, rutting resistance, anti-stripping performance, fatigue performance, and low temperature performance. The neat asphalt saving with CR was found to be 5.8% compared to unmodified asphalt. The fuel savings in this study was around 13%, and a visible hazard emission reduction was observed as well. The mechanical performance results showed that the CR-WMA with Evotherm had equivalent rutting resistance and low temperature performance and better fatigue performance and moisture damage resistance compared to the CR-HMA. The CR-WMA with Evotherm and CR-HMA had a higher tensile strength and better low temperature performance than the control HMA. In regard to the comparison between the CR-WMA and CR-HMA, the laboratory compacted and field collected samples were consistent overall. The results also indicated that the moisture damage resistance evaluated through the tensile strength ratio and the HWT may not perfectly agree with each other.

High temperature performance of SBS modified bio-asphalt

Abstract: Crude oil-based asphalt supplies are shrinking while its demand is increasing rapidly; this, in turn, has led to an increase in the price of asphalt binder. As the price of asphalt increases, seeking for alternative and renewable binder resources, such as bio-asphalt, has become a hot research topic. However, the high temperature performances of bio-asphalt are unsatisfactory according to many previous studies. This study aims to enhance the high temperature performance of bio-asphalt by adding SBS into the matrix asphalt. Five types of SBS modified bio-asphalts were studied. Studies included their viscosity, anti-rutting performance and temperature sensitivity through the rotational viscometer (RV) and dynamic shear rheometer (DSR). Among them, SBS dosage was 1% of SBS modified bio-asphalt and the 50 penetration grade binder was applied as the base binder. The bio-oil contents for the five types of binders were 0%, 5%, 10%, 15% and 20% by weight of the SBS modified bio-asphalt. It was found that SBS modified bio-asphalt had higher viscosity than the base binder to some degree, and the effect of bio-oil on SBS bio-binder viscosity was small when the bio-oil content and testing temperature were high. The mixing and compaction temperatures of SBS modified bio-asphalt were about the same as those of the 50# base binder when the bio-oil content was more than 10%. Before RTFO testing, the SBS bio-binder had more viscous characteristics and a lower anti-rutting performance, but was not significantly different from that of the base binder. However, an opposite trend was observed after the RTFO test. Meanwhile, SBS bio-binder was less sensitive to temperature than the base binder and such sensitivity decreased with the increase in bio-oil content before RTFO. After RTFO, the temperature sensitivity of the SBS bio-binder was still lower than that of the 50# base binder when bio-oil content was less than 20%, and grew with the increase in bio-oil content.

Laboratory investigation on chemical and rheological properties of bio-asphalt binders incorporating waste cooking oil

Abstract: Recent efforts are being conducted to develop alternative asphalt binders from various bio-mass resources for future flexible pavements construction due to their renewability and the increasing costs of conventional petroleum-based asphalt. The objective of this paper is to investigate the potential of using the waste cooking oil (WCO) based bio-oil as a modifier for petroleum based neat asphalt binder and Styrene-Butadiene-Styrene (SBS) modified binder by means of chemical and rheological approaches. A series of tests were conducted for such purpose, including the infrared spectroscopy test, frequency sweep rheological test, multiple stress creep recovery test, and linear amplitude sweep test. The infrared spectroscopy results indicate identical chemical functional groups between the bio-oil and the petroleum asphalt binder though acid, ether, ester and alcohol compounds were also observed within the bio-oil. The bio-oil modified binders display increased carbonyl index with increasing the bio-oil percent weight whereas the sulfoxide index almost exhibits the same level as that of the control asphalt. Frequency sweep tests show that the bio-oil addition obviously decreased the binder stiffness according to the dynamic shear modulus master curve. Due to this softening effect from the bio-oil modifier, the weakened rutting resistance of bio-binders are demonstrated for both neat and SBS binders at the high temperature range. The fatigue life of bio-binders at intermediate temperature under cyclic fatigue loading are found to be significantly improved by increasing bio-oil content but the binder yield energy simultaneously decreased. It can be preliminarily concluded that the WCO based bio-oil tested in this study could be used as a potential bio-modifier to produce a sustainable asphalt binder.

Optimization of bio-asphalt using bio-oil and distilled water

Abstract: The objective of this research is to improve the high temperature performances and anti-aging properties of bio-asphalt. In this paper, the bio-asphalt was prepared using bio-oil to modify petroleum asphalt, and the contents of bio-oil were 10%, 15%, 20%, 25% and 30%. The gas chromatograph-mass spectrometer (GC-MS) test was applied to characterize the chemical compounds in bio-oil. The Fourier transform infrared spectroscopy (FTIR) test was utilized to determine whether some compounds were removed from bio-oil based on the functional groups present. Then the rotating thin film oven (RTFO) test was used to verify whether the high temperature performance and anti-aging properties of bio-asphalt improved. Furthermore, the orthogonal experimental design and dynamic shear rheometer (DSR) test were employed to study the effect of optimization process parameters on high temperature performances. It was found that a large amount of polar light weighted components can be removed from bio-oil using distilled water. During the treatment process of bio-oil, the water-oil mass ratio had a significant influence on the high temperature of bio-asphalt while stirring time and stirring temperature were not significant factors. Additionally, the anti-rutting properties of bio-asphalt had an increasing trend when the water-oil mass ratio varied from 1:1 to 2:1 and reached a maximum when the water-oil mass ratio was 2:1.The bio-oil optimization process involved stirring the water-oil mix for 10 min at 50 °C with a water-oil mass ratio of 2:1. Using bio-oil and distilled water is reliable in optimizing bio-asphalt as the high temperature performance and anti-aging performance of bio-asphalt were improved after bio-oil was treated with distilled water.

Morphology, rheology, and physical properties of polymer-modified asphalt binders

Abstract: Asphalt binders play an integral role in the performance and properties of asphalt mixtures. Increased traffic-related factors on the roadways such as heavier loads, higher traffic volume, and higher tire pressure combined with substantial variation in daily and seasonal temperatures of the pavement have been responsible for the asphalt pavements failure. To prevent or mitigate these failures, many attempts have been made by polymer scientists and civil engineers to improve the performance of asphalt pavements by modifying the properties of asphalt binders. A good modifier changes the failure properties such that binder yields more stresses and strains before failure. Modification of asphalt binders through the addition of a polymer to improve their rheological and physical properties has a long history in asphalt industry. Once the polymer is properly mixed with the asphalt binder, a swallowed polymer network is formed, which contributes to the changes in viscoelastic behavior. However, polymer-modified asphalt binders may have some drawbacks related to the poor solubility of polymers. Understanding the internal structure of polymer-modified asphalt binders has been the subject of numerous research studies. Available studies regarding the affecting parameters on the properties of the polymer-modified asphalt binders are reviewed here. Various types of polymers used in asphalt industry and their effects on the rheological, morphological, physical and mechanical properties of polymer-modified asphalt binders are also discussed in this paper. In addition, this paper provides a review on the techniques used to overcome/mitigate the shortcomings of conventional polymer-modified asphalt binders.

Challenges and Opportunities for Bio-oil Refining: A Review

Abstract: Bio-oil derived from fast pyrolysis of lignocellulosic materials is among the most complex and inexpensive raw oils that can be produced today. Although commercial or demonstration scale fast pyrol...

Application of rejuvenators to improve the rheological and mechanical properties of asphalt binders and mixtures: A review

Abstract: The use of recycled materials such as Reclaimed Asphalt Pavement (RAP) and Recycled Asphalt Shingle (RAS) in asphalt pavements is a valuable approach to construct sustainable pavements and to preserve natural resources and energy. However, the use of high amounts of RAP and RAS can potentially cause durability-related distresses such as cracking and raveling due to the presence of severely aged asphalt binders. Rejuvenators have been widely used to overcome this issue and to mitigate the problems associated with the use of aged binders. They can improve the viscoelastic and rheological properties of asphalt mixtures containing RAP and RAS. Much has been learned about various types of rejuvenating agents, techniques to apply these agents, and challenges associated with their applications. This article reviews the literature on the applications of various types of rejuvenators in paving industry and their effects on the properties of the aged binders. The techniques for rejuvenating the aged asphalt binders and the mechanism of rejuvenation are also reviewed. Moreover, methods to determine the optimum rejuvenator content to achieve optimized mechanical and durability properties of the asphalt binders and mixtures are discussed. The findings in this research show that rejuvenators can be successfully used to restore the properties of the aged binders. It is hoped that this review will serve as a guidelines for pavement engineers to better design the asphalt mixtures containing rejuvenators. This review will also help scientists to find future avenues of research on the applications of rejuvenators in asphalt industry.

A review on solutions for improving rutting resistance of asphalt pavement and test methods

Abstract: Permanent deformation, mainly referring to rutting, is one of the main distress modes of asphalt pavement. Exploring effective methods to mitigate the rutting distress is of great significance for providing a long-life and safe road. The rutting solutions were first reviewed. It was found that the efforts from academic and engineering industries focused on enhancing the rheological properties of asphalt binder by adding modifying powder, fiber or mixture into binder or mixture, as well as strengthening aggregate interlock and applying novel pavement structure. Semi-flexible asphalt pavement was suggested to be a promising method to fight the rutting distress, because it has a high mechanical property without scarifying the flexibility of asphalt pavement. In order to consider the influence of temperature on rutting occurrence, cool asphalt pavements, especially heat-transfer induced structures, were reviewed and deemed to be a new strategy for reducing rutting susceptibility of asphalt pavement. In order to evaluate the effectiveness of above rutting solutions, many tests, such as multi-stress creep recovery test for asphalt binder and wheel tracking test for asphalt mixture, were reviewed. By linking the reported results of wheel tracking test with high-temperature rutting mechanism it was advised to develop a test method that could reproduce the real field pavement environment, including multiple stress mode, temperature gradient control system and pavement structure, to assess the rutting response of asphalt mixture. This review is expected to provide an overall insight on the existing rutting solutions and test methods, and recommend future studying areas relevant to rutting distress.

The impact of bio-oil as rejuvenator for aged asphalt binder

Abstract: Recycling technology has been widely applied on road pavement due to the aging problem of asphalt binder and the extensive requirement for maintenance. The aim of this research is to use bio-oil generated from sawdust as a rejuvenator to recycle aged asphalt. In this research, the performance graded asphalts PG 58-28 and PG 64-22 were selected as the base binders. The bio-oil contents were 10%, 15% and 20% of the total binder by weight. The Rotational Viscometer (RV) test, Dynamic Shear Rheometer (DSR) test, and Asphalt Binder Cracking Device (ABCD) test were applied to characterize the properties of bio-rejuvenated asphalts and virgin control asphalts. Additionally, the Fourier Transform Infrared Spectroscopy (FTIR) test was conducted to characterize the degree of restoration of aged asphalt binders from the aspect of functional groups. It was found that the bio-rejuvenator decreases the viscosity and activation energy, while increasing the temperature susceptibility and the content of viscous components of the aged asphalts. The aged asphalt can be softened by the bio-rejuvenator significantly; with the use of bio-rejuvenator, the rutting index of aged asphalts PAV PG 58-28 and PAV PG 64-22 at high temperatures from 52 °C to 76 °C was decreased by 75.5% and 77.2% in average, respectively. The bio-oil can restore the low temperature crack resistance of aged asphalts PAV PG 58-28 and PAV PG 64-22 to, or even better than, the level of virgin asphalts. The sulfoxide (S O) index and aromatic (C C) index can be used to evaluate the degree of restoration using bio-rejuvenator to recycle aged asphalt, but carbonyl (C O) is not applicable. Therefore, the bio-oil generated from sawdust can be used as a rejuvenator to recycle the aged asphalts PAV PG 58-28 and PAV PG 64-22. Moreover, the bio-rejuvenator contents of 15% and 20% are recommended to recycle the aged asphalt PAV PG 58-28 and aged asphalt PAV PG 64-22, respectively.