Low Temperature Performance Of Asphalt Research Articles

On the enhanced properties of composite asphalt via adding surface modified calcium sulfate whisker-SBR

With the aim of improving the durability and safety, erosion time, and cost-effective of asphalt road, a composite of modified calcium sulfate whisker-styrene butadiene rubber modified asphalt (MCSW-SBRMA) was prepared via thermal doping. Firstly, stearic acid and titanate coupling agent (NDZ-201) were used as a modifier to transform calcium sulfate whisker (CSW) into MCSW via wet modification method at 60 °C and anhydrous ethanol as a dispersant. What is more, the optimum loading of modifier (a mixture of 25% stearic acid + 75% NDZ-201) was found to be at 2% to prepare MCSW. Subsequently, a composite of MCSW-SBRMA was prepared with different loading of MCSW (i.e. 2% to 8%) to enhance the softening point of asphalt. In this study, it was found that 4% of modifiers was the best composition to improve the MCSW-SBRMA properties as elucidated in the orthogonal experiment table L16(42). The effects of MCSW and SBR addition on several properties of asphalt were studied by multiple routine tests including penetration, segregation test, and so on. The results show that: 2% to 8% MCSW can increase the softening point of SBR modified asphalt (SBRMA) by 7% to 8%. 4% MCSW increased the PG of SBRMA from 64 to 70, which greatly improved the high temperature characteristics of asphalt. The 5 °C ductility of MCSW-SBRMA is greater than 100 cm, which greatly improves the low temperature performance of asphalt. Through the application of fluorescence microscopy (FM), Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), and energy dispersive spectroscopy (SEM-EDS), it has been demonstrated that MCSW-SBR effectively alters asphalt in a highly uniform manner, with some MCSW still retaining large cross sections, thereby facilitating the dispersion of shear stress and enhancing the durability of asphalt.

Performance study of SBS/CRMA with different composite crumb rubber particle size ratios

Different crumb rubber (CR) particle sizes affect asphalt performance differently. To improve the performance of CR in SBS/CR composite modified asphalt (SBS/CRMA) and to study the enhancement of SBS/CRMA performance with varying ratios of composite CR particle sizes. This study employed three different configurations of SBS/CRMA composite ratios. Several tests and analyses were conducted, Brookfield viscosity measurements, conventional performance tests, storage stability, high- and low-temperature rheology, LAS, Fourier transform infrared spectroscopy (FTIR) and fluorescence microscopy (FM) analysis. The results indicated that, in the composite CR particle size ratio, a finer particle size of CR demonstrated more significant benefits in improving the high- and low-temperature performance of asphalt. However, with aging, the role of a coarse particle size of CR gradually became more prominent. Furthermore, compared to a single CR mesh SBS/CRMA, the 3 S + 5R-6:2:2 composite CR particle size ratio of SBS/CRMA exhibited superior high- and low-temperature deformation and fatigue resistance. Considering the microscopic analysis, it can be observed that the fine particle size of CR exhibited superior compatibility and anti-aging performance compared to the coarse particle size. In the composite CR particle size ratio, adjusting the proportion of coarse and fine CR particle size will improve the performance of SBS/CRMA significantly. Contrary to common belief, it was not necessarily true that a higher ratio of coarse CR particles leads to a better modification effect in SBS/CRMA. On the other hand, the composite CR particle size ratio proved significantly advantageous, thereby providing valuable guidance for enhancing the performance of SBS/CRMA.

Effect of concentration of polyphosphoric acid on the high and low temperature performance of asphalt

The purpose of this study is to gain a deeper understanding of PPA modified asphalt and to investigate the effect of PPA concentration on the high and low temperature performance of the asphalt. Four different concentration levels of PPA modified asphalt were prepared. The zero-shear viscosity (ZSV) at 60 ℃ was measured using a dynamic shear rheometer (DSR) to evaluate its high temperature performance. The creep parameters were measured using a bending beam rheometer (BBR), and the creep compliance derivative (J′(t)) was calculated based on the Burgers model to evaluate its low temperature performance. The statistical analysis method was used to discuss the significant difference in the effect of PPA concentration on the high and low temperature performances of asphalt. The modification mechanism of asphalt by PPA concentration was revealed using gel permeation chromatography (GPC) and differential scanning calorimetry (DSC). The results show that there is a significant difference in the effect of PPA concentration on viscosity. As the concentration increases, the viscosity also increases, leading to a more obvious improvement in high temperature performance. PPA can slightly improve the low temperature performance of asphalt, but the effect of PPA concentration on low temperature performance is not significant. PPA narrows the distribution range of asphalt molecular weight, and a large proportion of small molecular size is converted to medium molecular size, which increases the average molecular weight. There is a good linear relationship between the weight-average molecular weight (Mw) of PPA modified asphalt at different concentrations and the corresponding viscosity value. The glass transition temperature (Tg) of the PPA modified asphalt is slightly lower than that of the original asphalt. However, there is no notable difference in Tg among the PPA modified asphalts at different concentrations. These findings provide valuable guidance for the selection of raw materials for PPA modified asphalt.

Study on UV aging characteristics of low-grade asphalt in the desert climate

The Taklamakan Desert in China’s Xinjiang region faces severe heat conditions that cause rutting in asphalt pavements. In order to combat this issue, local construction management has been advocating for the utilization of low-grade asphalt with penetration levels between 20 and 50, to enhance the pavement’s resistance to rutting. However, there is limited research on the durability of low-grade asphalt under intense UV irradiation in the region. To this end, a multiscale investigation was conducted, examining three different types of asphalt (30#, 50#, and 70#), under various conditions such as virgin, UV aging, and Pressure Aging Vessel aging. Analytical techniques such as Atomic Force Microscope, Gel Permeation Chromatography, Fourier Transform Infrared Spectroscopy, Dynamic Shear Rheology, and Bending Beam Rheometer were employed. The results revealed that the surface roughness of the three types of asphalt increased by 15.50% (30#), 5.99% (50#), and 2.70% (70#) after UV aging, compared to the virgin samples. Furthermore, the adhesion properties of lower-grade asphalt were less affected by UV aging. Weight-average molecular weight of the three types of asphalt increased significantly after UV aging, with a 26.96% increase in 30#, 51.92% increase in 50#, and 43.76% increase in 70# compared to the samples prior to UV aging. The 30# asphalt with higher large molecule content exhibited slower UV aging. The 30# asphalt also exhibited the smallest increase of C=O and S=O after UV aging among the three types of asphalt. The study also found that UV aging had a lesser effect on the high- and low-temperature performance of asphalt, compared to PAV aging. Overall, the effects of UV irradiation on various properties of 30# asphalt were less pronounced than those of 50# and 70# asphalt. These findings offer valuable insights into aging resistance in the Taklamakan Desert, benefiting road contractors and the academic community.

Polyolefin Elastomer Modified Asphalt: Performance Characterization and Modification Mechanism

The rapid growth of traffic load and volume has put forward higher requirements for road durability. To extend the service life of roads, this work investigated the feasibility of using polyolefin elastomers with a two-phase molecular structure to simultaneously improve the high and low-temperature performance of asphalt. The characteristics of the polyolefin modifier were evaluated by differential scanning calorimetry first. Following evaluation, the storage stability, workability, and rheological properties of modified polyolefin-modified asphalt were measured through softening point difference, rotary viscosity, dynamic shear rheometer, and bending beam rheometer. Additionally, the engineering performance of modified asphalt mixtures was also investigated through Marshall stability, wheel-tracking, and three points bending experiments. The results show that polyolefin has two glass transition points which facilitate the simultaneous improvement of the high and low-temperature properties of asphalt. Meanwhile, no concerns are found about the storage stability and workability of polyolefin-modified asphalt. Furthermore, the results of rheological properties indicate that polyolefin can significantly enhance the deformation resistance at high-temperature and cracking resistance at low-temperature of asphalt binders. While the fatigue performance of the polyolefin-modified asphalt is slightly reduced, the residual Marshall stability, dynamic stability, and ultimate tensile strain of the asphalt mixture containing 8% polyolefin are 1.05 times, 1.31 times, and 1.17 times those of the control sample, respectively. The results of infrared spectroscopy demonstrate that there is no chemical reaction between the polyolefin-modified and the virgin asphalt. The improvement of polyolefin on asphalt performance can be explained by the existence of both “rigid” and “flexible” structures in polyolefin.

Biomass valorization toward sustainable asphalt pavements: Progress and prospects

To cope with the global climate crisis and assist in achieving the carbon neutrality, the use of biomass materials to fully or partially replace petroleum-based products and unrenewable resources is expected to become a widespread solution. Based on the analysis of the existing literature, this paper firstly classified biomass materials with potential application prospects in pavement engineering according to their application and summarized their respective preparation methods and characteristics. The pavement performance of asphalt mixtures with biomass materials was analyzed and summarized, and the economic and environmental benefits of bio-asphalt binder were evaluated. The analysis shows that pavement biomass materials with potential for practical application can be divided into three categories: bio-oil, bio-fiber, and bio-filler. Adding bio-oil to modify or extend the virgin asphalt binder can mostly improve the low temperature performance of asphalt binder. Adding styrene-butadienestyrene (SBS) or other preferable bio-components for composite modification will have a further improved effect. Most of the asphalt mixtures prepared by using bio-oil modified asphalt binders have improved the low temperature crack resistance and fatigue resistance of asphalt mixtures, but the high temperature stability and moisture resistance may decrease. As a rejuvenator, most bio-oils can restore the high and low temperature performance of aged asphalt and recycled asphalt mixture, and improve fatigue resistance. Adding bio-fiber could significantly improve the high temperature stability, low temperature crack resistance and moisture resistance of asphalt mixtures. Biochar as a bio-filler can slow down the asphalt aging process and some other bio-fillers can improve the high temperature stability and fatigue resistance of asphalt binders. Through calculation, it is found that the cost performance of bio-asphalt has the ability to surpass conventional asphalt and has economic benefits. The use of biomass materials for pavements not only reduces pollutants, but also reduces the dependence on petroleum-based products. It has significant environmental benefits and development potential.

Analysis of the Influence of Waste Seashell as Modified Materials on Asphalt Pavement Performance.

An increasing amount of waste seashells in China has caused serious environmental pollution and resource waste. This paper aims to solve these problems by using waste seashells as modified materials to prepare high-performance modified asphalt. In this study, seashell powder (SP) and stratum corneum-exfoliated seashell powder (SCESP) were adopted to prepare 10%, 20% and 30% of seashell powder-modified asphalt (SPMA) and stratum corneum-exfoliated seashell powder-modified asphalt (SCESPMA) by the high-speed shear apparatus, respectively. The appearance and composition of two kinds of SPs were observed and determined by the scanning electron microscope (SEM). The types of functional groups, temperature frequency characteristics, low temperature performance and adhesion of SPMA were tested by the Fourier-transform infrared (FTIR) spectrometer, dynamic shear rheometer (DSR), bending beam rheometer (BBR) and contact angle meter. The results show that the SP and SCESP are rough and porous, and their main component is CaCO3, which is physically miscible to asphalt. When the loading frequency ranges from 0.1 Hz to 10 Hz, the complex shear modulus (G*) and phase angle (δ) of SPMA and SCESPMA increase and decrease, respectively. At the same load frequency, SCESPMA has a larger G* and a smaller δ than SPMA. At the same temperature, SCESPMA has a larger rutting factor (G*/sin δ) and better high-temperature deformation resistance than SPMA. SP and SCESP reduce the low-temperature cracking resistance of asphalt, of which SCESP has a more adverse effect on the low-temperature performance of asphalt than SP. When SP and SCESP are mixed with asphalt, the cohesion work (Waa), adhesion work (Was) and comprehensive evaluation parameters of water stability (ER1, ER2 and ER3) of asphalt are improved. It is shown that both SP and SCESP have good water damage resistance, of which SCESP has better water damage resistance than SP. These research results have important reference value for the application of waste biological materials in asphalt pavement.

Reclamation of waste oils in asphalt modification towards enhanced low-temperature performance of pavement in cold region

ABSTRACT To decrease the usage of petroleum asphalt and improve waste recovery, two different groups of recycled oils were selected to improve the low-temperature performance of asphalt binders in cold region. The multiple stress creeps recovery (MSCR) test, linear amplitude sweep (LAS) test and bending beam rheometer (BBR) test were performed to evaluate the rheological properties of recycled oil modified asphalt (ROMA). The thermal stress and double edge notched tension (DENT) tests were employed to characterise the low-temperature cracking resistance and ductile resistance of the ROMA, respectively. The results of this study showed that recycled oils significantly improved the low-temperature and fatigue performance of asphalt, which is manifested in a drop in the low-temperature critical cracking temperature of asphalt by 3°C, increase in crack tip opening displacement (CTOD) by 72.8%, and extension of fatigue life by 178.9%. The addition of recycled oils reduced the percentage of large molecule size (LMS) while increasing the percentage of medium molecule size (MMS) of the asphalt, which contributes to the better low-temperature performance of the ROMA. The results from this study provide insights into the reclamation of waste oils and developing the low-temperature modifier of asphalt pavements in cold region.

Evaluation for Low Temperature Performance of SBS Modified Asphalt by Dynamic Shear Rheometer Method

Finding an alternative or supplementary test method to evaluating the low temperature performance of asphalt is an area of considerable interest. This paper tries to explore the possibility of using the dynamic shear rheometer (DSR) method for assessing the low temperature properties of styrenebutadienestyrene (SBS) modified asphalt. In the study, 60/80 and 80/100 pen grade asphalt binders, named binder A-70, binder B-70 and binder C-90, are used to produce the SBS modified asphalt samples. After that, the low temperature performance of the asphalt binders is characterized by using bending beam rheometer (BBR) test. The results indicate that the low temperature performance of the different binders is related to the source of the binder. The low temperature performance of asphalt could be improved with the addition of the SBS. The DSR test is used to develop the complex modulus master curves for binders. Based on the principle of time–temperature conversion, the glass transition temperature of asphalt is calculated by the Williams–Landel–Ferry (WLF) equation. The glass transition temperatures (Tg) of base asphalt and the SBS modified asphalt are determined by the viscoelastic parameters of the master curve and the WLF equation coefficients based on the time–temperature superposition principle. By establishing the relationship between the critical temperature and the Tg of the asphalt binder, the effectiveness of the method established in this paper is verified. The advantage of this method is the ability to use the DSR test for the rapid evaluation of the low temperature performance of asphalt, which is able to reduce testing materials and save testing time as well. The glass transition temperature of the SBS modified asphalt is closely associated with aging degree, asphalt source and the SBS content.

Multi-Objective Optimization and Performance Characterization of Asphalt Modified by Nanocomposite Flame-Retardant Based on Response Surface Methodology.

In order to improve the safety of the tunnel asphalt pavement in the event of a fire, and reduce the deterioration of the low temperature crack resistance of the asphalt by the flame retardant. The research uses aluminum hydroxide (ATH) as a smoke suppressant, diethyl aluminum hypophosphite (ADP) as a flame retardant, and halloysite nanotubes (HNTs) as a synergist to modified styrene-butadiene-styrene block copolymer (SBS) modified asphalt (MA). First, the content of ATH, ADP, and HNTs was used as the response variable. The physical properties (Penetration, Softening point, Ductility) and static flame retardant properties (Limiting oxygen index meter, Ignition point) of the asphalt modified by nanocomposite flame-retardant (HNTs-CFRMA) were the response variables. The response surface methodology was used to design the test, and regression models were established to analyze the influence of flame retardants on the performance of asphalt. Then, comprehensively considering the effects of physical properties and flame retardant properties, the normalized desirability function was used to perform a multi-objective optimization design on the components of the nanocomposite flame retardant modifier to obtain the best flame retardant formula. Finally, the rheological properties of MA, conventional flame-retardant modified asphalt (CFRMA), and HNTs-CFRMA were tested based on Dynamic shear rheometer, Multiple stress creep test, Force ductility tester, and Bending beam rheometer. The performance of flame-retardant and smoke suppression were tested by the Cone calorimeter tests. The result shows that ATH, ADP, and HNTs can enhance the high temperature performance of asphalt, reduce the penetration. The addition of HNTs can increase significantly the softening point and reduce the deteriorating effect of flame retardants on the low temperature performance of asphalt; the addition of ATH and HNTs can improve significantly the flame retardancy of asphalt. Based on the desirability function of power exponent, the formulation of the nanocomposite flame retardant with better physical properties and flame retardant properties is ATH:ADP:HNTs = 3:5:1, and the total content is 9 wt%. Nanocomposite flame retardants can improve obviously the high temperature rheological properties of asphalt. The rutting factor and the cracking factor of HNTs-CFRMA improve markedly, and the irrecoverable creep compliance is reduced, compared with MA and CFRMA. Nanocomposite flame retardant can make up for the deterioration of conventional flame retardants on asphalt’s low temperature performance. At the same time, it has better flame-retardant performance and smoke suppression performance.

Evaluation of VOCs inhibited effects and rheological properties of asphalt with high-content waste rubber powder

Waste rubber powder (WRP) has become a widely used and sustainable replacement for asphalt modifier. At present, the mixing content of WRP in waste rubber modified asphalt (WRMA) is basically between 18 and 22%, while the high-content (25–45%) WRP modified asphalt (HC-WRMA) can realize the high added value utilization of solid waste and show excellent high temperature properties at the same time. However, more volatile organic compounds (VOCs) will be generated with the increase of the content of WRP, which would lead to environment pollution. This research aimed to explore the optimal mixing content of WRP in asphalt and how to effectively suppress the VOCs produced of HC-WRMA. First, the compatibility between WRP and asphalt was analyzed for HC-WRMA. Then, different VOCs inhibitors including activated carbon, 4A zeolite and nano calcium carbonate were added into HC-WRMA to inhibit VOCs emission. In addition, the high temperature rheological properties of HC-WRMA were studied using dynamic shear rheometer (DSR) and the low temperature properties of HC-WRMA were studied using differential scanning calorimetry (DSC). The optimum contents of WRP are 35% according to the storage stability experiments results. The GC–MS results show that different inhibitors have a significant inhibited effect on asphalt VOCs, and the addition of 6% nano calcium carbonate has the best inhibited effect. The DSR results show that complex modulus of HC-WRMA increased gradually with the increase of WRP content, and the phase angle decreased with the increase of WRP content, which indicates that the addition of WRP can improve the resistance deformation ability of asphalt and enhance the flexibility of asphalt. The DSC results show that the addition of excessive WRP has adverse effect on the low temperature performance of asphalt. Also, the Fourier transform infrared spectroscopy (FT-IR) results show that there are no chemical reaction and only physical blending between the WRP and asphalt. In short, HC-WRMA has broad development prospects in the future.

Study on Performance Damage and Mechanism Analysis of Asphalt under Action of Chloride Salt Erosion.

This study aims to investigate the performance evolution and mechanism of asphalt under action of chloride salt erosion. Asphalt samples soaked with five different snow melting chloride salt concentrations were taken as the research object. Then, the high-temperature performance, low-temperature performance, temperature sensitivity and asphalt–aggregate adhesion property of asphalt samples were carried out. Additionally, Fourier transform infrared spectroscopy (FTIR) was used to explore the mechanism of chloride salt erosion on asphalt. Test results showed the linear variation relationships of high-temperature performance, low-temperature performance and temperature sensitivity with chloride salt concentrations. The high-temperature performance of asphalt would be improved by chloride snowmelt salt. With the increase in the chloride salt solution concentration, the low-temperature performance of asphalt became worse, and the temperature sensitivity increased. Moreover, after the effect of the chloride salt solution, the asphalt–aggregate adhesion property decreased with the increase in the chloride salt solution concentration. It is necessary to control the amount of chloride snowmelt salt in the actual snow removal projects. Finally, based on Fourier transform infrared spectroscopy, the mechanism of chloride salt erosion on asphalt was preliminarily explored. With the increase in the chloride salt solution concentration, the proportion of light components (saturated fraction, aromatic fraction) in asphalt decreased, and the proportion of heavy components (resin and asphaltene) with good thermal stability increased.

Effect of physical hardening on low temperature performance of DCLR modified asphalt

This study aims to investigate the effect of physical hardening on the low temperature performance of direct coal liquefaction residue (DCLR) modified asphalt. The extended bending beam rheometer (EBBR) method was used to evaluate the low temperature performance of DCLR modified asphalt with benzaldehyde, silane coupling agent and xylene compatibilizer. Meanwhile, the microstructure and morphology of DCLR modified asphalt before and after physical hardening were quantitatively characterized by atomic force microscope (AFM) and image processing software. In this study, the physical hardening was performed by placing the DCLR modified asphalt at low temperature conditions for a certain time. The test results show that as the conditioning temperature decreased and the conditioning period increased, both low temperature grade loss and hardening rate of asphalt increased, indicating that the low temperature performance deteriorated. Compared to the room-temperature conditions, the total number of “bee-structures” of DCLR modified asphalt under low temperature conditions were less, but the shape of a single “bee-structure” became larger and longer. The compatibilizers hindered the growth of “bee-structure”, which demonstrated that the compatibilizers could improve the low temperature performance of asphalt. The three compatibilizers had different effects on low temperature performance of DCLR modified asphalt. Among them, the silane coupling agent was the most effective, followed by benzaldehyde and xylene.

Study on Preparation Method of Terminal Blend Rubberized Asphalt Binder

Terminal Blend rubberized asphalt binder is generally prepared under high temperature conditions. Unlike asphalt plants that produce asphalt in sealed asphalt tanks, the process of laboratory interaction of asphalt and crumb rubber is mostly in contact with air, which can easily cause asphalt aging. To alleviate this phenomenon, TB-B and TB-C asphalt were prepared using crumb rubber in a nitrogen environment and soluble crumb rubber in an atmospheric environment, respectively.As a comparison group, TB-A asphalt was prepared using crumb rubber under atmospheric environment. A practical method for preparing TB asphalt was explored by changing the amount of crumb rubber and the interaction temperature. Their rheological characteristics were measured by dynamic mechanical methods using dynamic shear rheometer (DSR) and binding beam rheometer (BBR). It was found that under high interaction conditions, the crumb rubber in TB-A asphalt undergoes desulfurization and degradation reactions, which caused the hinge structure in the asphalt to be damaged and the high-temperature performance decreased. But the aliphatic compounds generated by the degradation of crumb rubber are beneficial to improve the low temperature performance of asphalt. Through polymer isolation experiments, it was found that the degradation of crumb rubber caused TB-A and TB-B asphalt to form a homogeneous system. While the soluble crumb rubber in TB-C asphalt was mainly swelling reaction, so the larger the amount of soluble crumb rubber, the more severe the segregation. Besides, the aging degree of three TB asphalts was studied by using viscosity experiments, thermal analysis and Fourier transform infrared (FT-IR) spectroscopy. The results show that compared with TB-A asphalt, the aging degree of TB-B and TB-C asphalt is greatly reduced. Therefore, both preparation methods effectively alleviate the aging phenomenon in the laboratory preparation of TB asphalt.

Study of the high and low-temperature behavior of asphalt based on a performance grading system in Northeast China

The performance of asphalt pavement mainly depends on the performance of the asphalt binder material used to construct them. Asphalt traditionally is characterized in terms of its empirical properties, such as penetration and softening point. However, this characteristic is not sufficient for a comprehensive and performance-based assessment of asphalt over a wide range of temperatures, nor for damage such as rutting and low temperature cracking. The objective of this research is to determine temperature conversion formulas, PG climate zones, and a PGm-n grading system for asphalt in northeastern China by analysis of air and pavement temperatures. On the basis of this analysis, the high and low temperature performance of asphalt (mixture) is evaluated. The research results have certain theoretical and practical value for improving the low and high temperature performance of asphalt binder, and have certain economic and social benefits.

Study on rheological properties and phase-change temperature control of asphalt modified by polyurethane solid–solid phase change material

Polyurethane solid–solid phase change material (PCM) with low phase change temperature is synthesized via prepolymer method. The synthetic polyurethane solid–solid PCM had lower crystallinity than PTMEG2000. The polyurethane solid–solid PCM was still in solid state during the heating process, and no liquid leakage was observed. After many phase change cycles, the polyurethane solid–solid PCM exhibited good stability of phase change cycles. Hence, the asphalt modified by polyurethane solid–solid PCM was prepared by high-speed shearing method. With increasing polyurethane solid–solid PCM proportion, the high temperature deformation resistance of modified asphalt gradually increased. At low temperature (<−18 °C), the addition of the polyurethane solid–solid PCM improved the low temperature performance of asphalt. With increasing polyurethane solid–solid PCM proportion, the specific heat capacity of the modified asphalt gradually increased. When the polyurethane solid–solid PCM proportion was >3 wt%, the specific heat capacity of the modified asphalt had an evident peak ranging from 13 °C to 25 °C. In the range of the proportion, the coefficient of the heat conductivity of the modified asphalt gradually increased with increasing PCM content. During the cooling process, the modified asphalt cooled relatively slow before the phase transition of the polyurethane solid–solid PCM. With continued decrease in the temperature, the phase transition of the polyurethane solid–solid PCM occurred, and the cooling rate of the modified asphalt further decreased. With increasing polyurethane solid–solid PCM content, the temperature control ability of modified asphalt and the efficiency of temperature control gradually increased.

Effect of ultraviolet absorber (UV-531) on the properties of SBS-modified asphalt with different block ratios

SBS modified asphalt with different block ratios (40/60, 30/70, 20/80) was prepared using a high-speed shearing apparatus to study the effect of the ultraviolet absorber (UV-531) on its properties. A melt blending method was used to prepare the modified asphalt with three doses of UV-531. The ultraviolet aging of asphalt was simulated in an indoor chamber. Dynamic shear rheological test, bending beam rheological test and force ductility test were used to assess the effects of different doses of UV-531 on high and low temperature performance of asphalt material modified with SBS of different block ratios. The results showed that UV-531 has little effect on the complex shear modulus of SBS-modified asphalt, and has a great influence on the phase angle of SBS-modified asphalt. The structural characteristics of SBS modifier is an important factor affecting the rheological properties at high temperature. UV-531 affects the distribution state of SBS modified medium hard segment (S) and soft segment (B) in asphalt, and has great influence on the low temperature performance of SBS-modified asphalt with different block ratios. The degree of aging and chemical changes in the UV-SBS modified asphalt were studied according to its softening point increment (SPI), complex shear modulus aging index (G*AI), infrared spectrum and scanning electron microscope. These results suggest that the degradation reaction of SBS modifier under UV leads to a significant reduction of polybutadiene segment (B) and cracking of SBS-modified asphalt. UV-531 can effectively reduce the aging of SBS-modified asphalt and prevent the decomposition reaction of SBS modifier in asphalt.

Evaluation on low temperature characteristics of SBS/CR modified asphalt binder under different aging conditions

This study discussed the low temperature performance of styrene–butadiene–styrene (SBS)/crumb rubber (CR) modified asphalt under different aging process. The bending beam rheometer (BBR) test was conducted to compare the low temperature performance of SBS and SBS/CR modified asphalt at three different temperatures. The continuous low service temperature of two modified asphalt binders was calculated based on the ASTM method. The simple fractional viscoelastic model was implemented to better describe the creep behaviour of asphalt at low temperatures from the BBR test results. The damping ratio and dissipated energy ratio were also derived from the simple fractional model to assess the low temperature performance of asphalt from the aspect of energy. The analysis results showed that adding CR to SBS modified asphalt was beneficial to reduce the low service temperature and increase the values of damping ratio and dissipated energy ratio before and after the aging process. It has been proved that the low temperature performance of SBS/CR modified asphalt is much better than that of SBS modified asphalt under different aging conditions.

Laboratory investigation on low-temperature performance of asphalt at different aging stages

This paper seeks to introduce an Improved Simple Aging Test (ISAT) as a new method for short-term and long-term aging of asphalt binder. Two kinds of asphalt, SK and ZH, were selected to be aged in the laboratory with the ISAT. The properties of the aged asphalt were investigated, including the high-temperature viscoelastic behavior, low-temperature performance and chemical composition. Moreover, the high-temperature viscoelastic behavior of the aged asphalt with different aging methods (IAST, Rotated thin Film Oven Test (RTFOT), and Pressurized Aging Vessel (PAV)) were also examined. The results show that aged asphalt in ISAT for 120 min at 163 °C have a similar viscoelastic behavior compared with the RTFOT, meanwhile the same conclusion between ISAT for 72 h at 95 °C and PAV can be drawn. By increasing the aging time, the low-temperature performance of the asphalt becomes worsen. At the beginning of the aging process, the performance reduces at a fast nonlinear rate, later the rate becomes constant. When compared with the asphalt SK, the asphalt ZH has a superior low-temperature performance and an inferior reduced rate in its performance at different aging stages. According to the chemical composition analysis of asphalts, the results described above can be well explained from the mechanism.

Preparation and Characteristics of Ethylene Bis(Stearamide)-Based Graphene-Modified Asphalt.

In this study, graphene-modified asphalt (GMA) was prepared from SK-70# matrix asphalt and ethylene bis(stearamide) (EBS). Based on the uniform design method, a model was created using Data Processing System (DPS) software and First Optimization (1stOpt) software using the graphene mixing amount, EBS mixing amount, shear rate, shear time, and shear temperature as factors and using the asphalt penetration, softening point, force ductility, SHRP-PG test, and multistress creep recovery data as indices. Calculations and analysis showed that the optimal composition and preparation parameters of GMA are as follows: the graphene proportion is 20‰, the EBS proportion is 1%, the shear rate is 6000 r.p.m., the shear time is 180 min, and the shear temperature is 140 °C. The prepared GMA had a significantly improved softening point, low-temperature fracture energy, antirutting factor, and creep recovery rate, indicating that adding graphene can improve the high- and low-temperature performance of asphalt. The prepared GMA was characterized by X-ray diffraction (XRD). The dispersibility of graphene in asphalt was evaluated by fluorescence microscopy and Image-Pro Plus imaging software. The results show that graphene can exist in asphalt in a stable form, which increases the loose-layered structure of stacked asphalt or gum. The intense adsorption effect of graphene strengthens the ordered structure of asphalt. However, due to its dispersibility characteristics, some graphene exists in asphalt in clustered form. When the graphene-to-dispersant ratio approaches the optimal value, the dispersant changes the form of graphene in asphalt from irregular clusters to regular clusters and from large, distinct clusters to small, indistinct clusters. When dispersant cannot uniformly disperse graphene in asphalt, graphene clusters primarily form medium-sized grains.