Hainian Wang

Bio: Hainian Wang is an academic researcher from Chang'an University. The author has contributed to research in topics: Asphalt & Crumb rubber. The author has an hindex of 26, co-authored 105 publications receiving 2081 citations.

Laboratory evaluation on high temperature viscosity and low temperature stiffness of asphalt binder with high percent scrap tire rubber

Abstract: The objective of this research is to utilize crumb rubber from scrap tires as an environmental friendly and sustainable additive for enhancing the high temperature and low temperature rheological properties of asphalt binders for asphalt pavements. Two different crumb rubber sources with different gradations – fine and coarse – were used in this project. The crumb rubber-modified (CRM) binder was produced by adding 10, 15, 20 and 25% crumb rubber particles by weight of a Superpave PG 64-22 asphalt binder. The CRM binders with and without Rolling Thin Film Oven (RTFO) aging were characterized by the AASHTO rotational viscosity test at 135, 140, 150, 160, 170, 177, and 190 °C (AASHTO T316). Furthermore, the low temperature cracking resistance of the binders was evaluated using the AASHTO Bending Beam Rheometer (BBR) test procedure at −12 and −18 °C (AASHTO T313). The statistical analysis of variance (ANOVA) was applied to quantify the effect of the influencing factors such as temperature, rubber particle size, and rubber concentration on the CRM binders’ performance. From the laboratory tests and ANOVA results in this study, it is evident that the addition of crumb rubber into asphalt binder can both significantly improve the viscosity of binder at high temperature and lower the creep stiffness at low temperature, which is beneficial to better both high temperature stability and low temperature cracking resistance of asphalt pavements. After RTFO aging, the viscosity decreases with increasing rubber concentration. Finer crumb rubber attains higher viscosity at high temperature and lower creep stiffness at low temperature. Considering the viscosity–temperature relationship, RTFO aging effects, creep stiffness decreasing percentage, and economical factors, 15% to 20% rubber asphalt ratio is proposed for the production of CRM binder.

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.

Rheological property investigations for polymer and polyphosphoric acid modified asphalt binders at high temperatures

Abstract: Polymer modified asphalt binders have been used with success in mitigating many major causes of asphalt pavement failures (e.g., permanent deformation, moisture induced damage, fatigue, etc.). The styrene butadiene styrene (SBS) is commonly used for producing PG 76-22 binder, but the market was hit with a shortage of butadiene back in late 2009, which affected both supply and cost of PG 76-22 throughout the entire United States. Therefore, some alternative modifiers such as elastomers, plastomers, recycled ground tire rubber, sulfur additives, and polyphosphoric acid (PPA) to substitute for SBS in PG 76-22 asphalt binders have been investigated for future applications in the industry. The objective of this study was to investigate the high temperature rheological properties of SBS and three alternative polymer modified binders with/without PPA. Two base asphalt binders (PG 64-22), four polymers, and one PPA were used to produce the modified binders. The tested rheological properties include rotational viscosity, fail temperature, G * /sin δ , phase angle, viscometry, amplitude sweep, frequency sweep, creep and creep recovery, and relaxation. The test results indicated that the PG 76-22 binders with two alternative polymers had noticeably lower viscosity values compared to SBS modified binders and thus need lower energy for mixing and compaction. In addition, for the binders used in this research work, the utilization of 0.5% PPA could reduce by 1.0% of additional polymer needed to produce the PG 76-22 binder. Moreover, the characteristics of viscometry, amplitude sweep, frequency sweep, creep and creep recovery, and relaxation spectrums of all modified binders were generally dependent upon polymer type, asphalt source, and test temperature.

Analysis on fatigue crack growth laws for crumb rubber modified (CRM) asphalt mixture

Abstract: In recent years, crumb rubber has been applied widely in asphalt pavement, and many researchers have indicated that crumb rubber modified (CRM) asphalt mixture is an environmentally friendly material. In this study, the notched semi-circular bending (SCB) test was employed to study the fatigue cracking property for CRM asphalt mixture. Then the cracking growth length was obtained by image processing technology, and its correlation with the fatigue number was established and studied in this paper. Concurrently, the influence of gradation type, asphalt content, test temperature, stress ratio, loading frequency, rubber powder concentration and rubber powder size on CRM asphalt mixtures’ fatigue life and crack growth laws were investigated by this method. The results indicated that the gap-graded CRM asphalt mixture had a longer fatigue life and a lower crack growth rate than the continuous graded mixtures Moreover, at the optimum asphalt content, the fatigue life was much longer and the crack growth rate was much lower at smaller loading times with higher loading frequency at the CRM asphalt mixture concentration of 20% using the smaller 80 mesh fine crumb rubber size.

Effect of warm mixture asphalt (WMA) additives on high failure temperature properties for crumb rubber modified (CRM) binders

Abstract: This paper investigates the effect of three warm mixture asphalt (WMA) additives on the high temperature rheological properties of both unaged and rolling thin film oven (RTFO) aged crumb rubber modified (CRM) binders. The WMA additives used in this study include Sasobit, RH and Advera. The ambient 40-mesh tire rubber with the concentrations of 10%, 15%, 20%, and 25% by the weight of asphalt binder, respectively, was used in this study. Dynamic shear rheometer (DSR) was employed to measure the complex modulus (G∗) and phase angle (δ) of CRM binders at various testing temperatures. The statistical analysis of variance (ANOVA) was applied to quantify the effects of WMA additives on the CRM binders’ rutting resistance properties. It was found in this study that, the three WMA additives could all improve the CRM binders’ resistance to rutting, and greatly improved high-temperature portion of the performance grade (PG) of CRM binders. It is found that Sasobit had the most remarkable effect on G∗ of both unaged and RTFO-aged CRM binders, RH only had significant effect on G∗ of RTFO-aged binders, Advera’s effect was indistinctive. Furthermore, WMA additives’ effect on δ was not conclusive.

Recycling of waste tire rubber in asphalt and portland cement concrete: An overview

Abstract: Waste tires pose significant health and environmental concerns if not recycled and/or discarded properly. Over the years, recycling waste tires into civil engineering applications, especially into asphalt paving mixtures and portland cement concrete, has been gaining more and more interests. This review summarizes the recent advances in the use of waste tire rubber in asphalt and portland cement concrete. The use of crumb rubber in asphalt paving mixture has long been proven successful due to good compatibility and interaction between rubber particles and asphalt binder, leading to various improved properties and performance of asphalt mixtures. The rubberized asphalt mixtures also have shown good compatibility with two widely used sustainability technologies in asphalt paving industry – reclaimed asphalt pavement (RAP) and warm-mix asphalt (WMA). In comparison with its use in asphalt paving mixtures, recycling of waste rubber in Portland cement concrete has not been so successful due to two factors: (1) incompatibility in chemical property between rubber and cement paste and (2) the significant difference in stiffness resulting in stress concentrations. Various methods have been proposed to overcome the barriers to improve the performance of rubberized portland cement concrete, some of which have shown to be promising.

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.

Rheological Properties and Chemical Bonding of Asphalt Modified with Nanosilica

Abstract: The objective of this study is to evaluate the rheological properties and chemical bonding of nano-modified asphalt binders blended with nanosilica In this study, the nanosilica was added to the control asphalt at contents of 4% and 6% based on the weight of asphalt binders Superpave binder and mixture tests were utilized in this study to estimate the characteristics of the nano-modifed asphalt binder and mixture The rotational viscosity (RV), dynamic shear rheometer (DSR), bending beam rhometer (BBR), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), asphalt pavement analyzer (APA), dynamic modulus (DM) and flow number (FN) tests were used to analyze rheological properties and chemical bonding changes of the nano-modified asphalt binder and the performance of the nano-modified asphalt mixture In addition, the performance of nano-modified asphalt after rolling thin-film oven (RTFO) short-term and pressure-aging vessel (PAV) long-term aging was assessed as well

Evaluation of aging behaviors of asphalt binders through different rheological indices

Abstract: The performance of asphalt pavement is seriously affected by aging of asphalt binder, so indices are expected which can not only evaluate aging resistance of asphalt binder but also indicate asphalt mixture performance. The objective of this paper was just to investigate effects of different rheological indices which present tighter and clearer correlation with asphalt mixture performance in evaluating asphalt binder aging behaviors, these indices including complex modulus (G∗) and phase angle (δ) master curves, rutting factor (G∗/sinδ), zero shear viscosity (ZSV), non-recoverable compliance (Jnr), fatigue factor (G∗·sinδ) and DSR function (DSRFn). Thin film oven test (TFOT), pressure aging vessel (PAV) test and ultraviolet (UV) irradiation were applied to simulate short-term, long-term thermal oxidation and photo oxidation aging, respectively. Frequency sweep tests and multiple stress creep recovery (MSCR) tests were conducted on three asphalt binders (60/80 pen grade base asphalt, styrene–butadiene-styrenecopolymer (SBS) modified asphalt and styrene butadiene rubber (SBR) modified asphalt) at different aging conditions. Meanwhile, aging sensitivities shown by different rheological indices were compared. The relationships between rheological indices were also discussed. The results showed that the ranking of aging resistances among asphalt binders evaluated by different rheological indices were nearly consistent and SBS modified asphalt exhibited the best aging resistance to three aging methods. Jnr and δ tended to decrease with the growth of aging severity, whereas other rheological indices were just contrary to this trend. Moreover, DSRFn proved to be the most sensitive index to aging. Based on correlation analyses, three groups of indices exhibited a strong correlation to each other, namely DSRFn versus G∗/sinδ, Jnr (0.1 kPa) versus Jnr (3.2 kPa) and Jnr (0.1 kPa) versus ZSV.

Influence of Six Rejuvenators on the Performance Properties of Reclaimed Asphalt Pavement (RAP) Binder and 100% Recycled Asphalt Mixtures

Abstract: 100% recycled hot mix asphalt lab samples were modified with five generic and one proprietary rejuvenators at 12% dose and tested for binder and mixture properties. Waste Vegetable Oil, Waste Vegetable Grease, Organic Oil, Distilled Tall Oil, and Aromatic Extract reduced the Superpave performance grade (PG) from 94–12 of extracted binder to PG 64-22 while waste engine oil required higher dose. All products ensured excellent rutting resistance while providing longer fatigue life when compared to virgin mixtures and most lowered critical cracking temperature. Rejuvenated samples required more compaction energy compared to virgin and some oils reduced moisture resistance slightly.