Multi-stress Creep Recovery Research Articles

Performance evaluation of bio-oil and high rubber content modified asphalt: More effective waste utilization

In this study, the bio-oil was used to reduce the viscosity and preparation temperature of high content of rubber-modified asphalt. The high rubber content modified bio-asphalt (RMBA) was prepared, the rubber and bio-oil contents were 20 %-30 % and 5 %-15 % (mass ratio of neat asphalt), respectively. The viscosity, temperature sweep (TS), frequency sweep (FS), multi-stress creep recovery (MSCR), and bending beam rheometer (BBR) tests were performed to assess the properties of RMBA. The Fourier Transform infrared spectroscopy (FTIR), Fluorescence microscopy (FM), and Scanning electron microscope (SEM) tests were conducted to explore the microscopic morphology of RMBA. Besides, the economic analysis and life cycle assessment (LCA) were assessed. Bio-oil contributed to the viscosity-reduction of the RMBA. When the rubber content was 30 %, the viscosity decreased by 48.16 % with a bio-oil content of 15 %. The temperature and frequency sensitivity of RMBA were lower than neat asphalt. Rubber improved the creep recovery and anti-rutting deformation behavior for bio-asphalt. The absorption peaks appeared at 1010 and 1038 cm−1, which represented the SO function group. The rubber did not absorb enough bio-oil for solubilization. This resulted in the functional group of SO appeared in 30 %+B-10 % and R-30 %+B-15 %. FM and SEM test results indicated that the rubber in RMBA exists in different states: undissolved rubber and dissolved rubber. The high content rubber could be partially dissolved in bio-asphalt and retained its elastic properties. The dissolved rubber particles exhibited a large crosslinked network structure. The raw material cost of RMBA decreased significantly with the rise of rubber and bio-oil contents. The reasonable application of waste rubber is beneficial to the alleviation of black pollution. The efficient application of rubber and bio-oil could contribute to the development of waste utilization and green transportation.

Evaluation of foaming performance for polymer modified and virgin asphalt binders

The pavement suffers rapid deterioration as a result of the weak bonding strength exhibited by the foamed virgin asphalt in the mixture. Consequently, it is crucial to develop a modified asphalt suitable for foaming. The expansion height and bubble size of foamed asphalt can be continuously and simultaneously monitored by binocular ranging equipment. By analyzing these dynamic responses, the evolution of the spatial domain expansion characteristics and the geometric features of the surface bubbles of foamed thermoplastic resin modified asphalt (TRA) was analyzed. Meanwhile, multi-stress creep recovery (MSCR) and bending beam rheometer (BBR) tests were conducted to analyze its rheological properties. Subsequently, the dispersibility of foamed TRA in the mixture was explored. The results showed that thermoplastic resin significantly improved the physical performance stability of foamed asphalt, as evidenced by an increase in its half-life by 2–3 times compared to the virgin asphalt when the dosage of thermoplastic resin reached 8 %. Foamed modified asphalt has fewer bubbles, but it has larger bubble sizes and more uniform distribution of bubbles. Meanwhile, the TRA exhibited excellent high-temperature deformation resistance and elastic recovery ability. The dispersion uniformity of foamed TRA in the mixture was superior to that of virgin asphalt. This study serves as a valuable reference for the exploration of foaming behavior in modified asphalt and the utilization of foamed modified asphalt in the mixture.

Preparation and Properties of Waterborne Polyurethane and SBS Composite-Modified Emulsified Asphalt

To address the issue of insufficient durability of traditional modified emulsified asphalt in the application of cold mix and cold paving anti-skid wear layers, this study utilizes cationic waterborne polyurethane (PU+) for composite modification to enhance adhesion and performance across a range of temperatures. Initially, composite-modified emulsified asphalt samples were prepared with varying dosages of PU+ according to a gradient method. Routine performance tests were conducted on the evaporated residues for analysis. Advanced rheological tests, including temperature sweep (TS), frequency sweep (FS), linear amplitude sweep (LAS), and multi-stress creep recovery (MSCR) tests, were performed using a dynamic shear rheometer (DSR). Surface free energy (SFE) tests were conducted with a fully automated surface tension meter (STM). A comprehensive evaluation of the high-temperature rheological properties, fatigue properties, adhesion properties, and water damage resistance of the modified emulsified asphalt residues was carried out. Chemical changes before and after modification were characterized using Fourier transform infrared spectroscopy (FTIR), and the distribution of polymers in the evaporated residue was observed using fluorescence microscopy (FM). The results demonstrated that cationic waterborne polyurethane significantly enhanced the fatigue and adhesion properties of SBS-modified emulsified asphalt, but it also weakened the water damage resistance of asphalt. MSCR tests revealed that the addition of cationic waterborne polyurethane might reduce the elastic recovery performance of modified asphalt, thereby weakening its resistance to rutting. Among the samples, the modified asphalt with a PU+ content of 6% exhibited good high-temperature shear resistance and elastic recovery performance, demonstrating the best anti-rutting performance.

Investigating the influence of stress dependency on the evaluation of high-temperature deformation resistance in SBS-modified asphalt

The rheological responses of Styrene-Butadiene-Styrene (SBS) modified asphalt are stress-dependent, yet the underlying mechanisms and their relationship to the phase structures formed by SBS in the asphalt matrix remain unclear. To address this issue, this study utilized varying dosages of SBS to prepare binders (SBSMA), which were then characterized through fluorescence microscopy, FTIR, and rheological tests including temperature sweeps and Multi-Stress Creep Recovery (MSCR) at four stress levels. Additionally, rutting resistance of the mixtures was evaluated using wheel tracking tests, correlating the results with rheological data. The test results indicate that the formation of a three-dimensional SBS network structure within the asphalt significantly increases the Stress Sensitivity Index (SSI) by 69.5 %, thereby enhancing the binder's stress sensitivity. Based on the theory of entropic elasticity, the stress sensitivity of SBSMA is explained. The cross-linked network structure exhibits superelastic behavior under low stress but may be overstretched and reorganized under high stress, leading to weakened entropic elasticity. Furthermore, the Jnr values obtained at higher stress levels show stronger correlation (r > 0.9) with the Dynamic Stability (DS) from the wheel tracking test results. This finding suggests that entropic elasticity does not significantly improve the rutting resistance performance at the mixture level. Consequently, increasing the stress level in MSCR tests is recommended to more accurately predict the binder’s rutting performance by inhibiting the network's entropic elasticity.

Evaluation of the effect of different preparation processes on the road performance of thermoplastic resin modified porous asphalt mixtures

In order to evaluate the effects of three preparation processes, namely dry process (DP), wet process (WP) and wet/dry mixing process (MP), and resin high viscosity modifier (RHVM) on the road performance of porous asphalt mixtures, the frequency scanning, multi-stress creep recovery, and bending beam rheometer tests were used to analyze the rheological performance of resin-modified high viscosity asphalt under different processes. Uniaxial compression, Wheel tracking, Semi-circular bending and Freeze-thaw indirect tensile tests were used to test the properties of resin-modified porous asphalt mixtures under different processes. The commonly used TAFPACK-Super (TPS) modifier was a control group. Finally, the changes in the microscopic morphology characteristics and chemical composition were used to illustrate the enhancement mechanism of resin modifiers. The results showed that the high-temperature deformation resistance and low-temperature cracking resistance of RHVM modified asphalt prepared by DP and MP are weaker than that of the WP. Compared to the RHVM(WP), the Jnr(3.2) of RHVM(DP) and RHVM(WP) decreased by 14.3% and 63.8%, the strength modulus of RHVM(DP) and RHVM(MP) increased by 21.5%, 28.0% and the creep rate decreased by 2.37%, 4.45%, respectively. As for the performance of asphalt mixture, compared to the RHVM(WP) asphalt mixture, the dynamic stability of RHVM asphalt mixture prepared by the DP and MP decreased by 17.3–18.2%, σs and εs of RHVM(DP) and RHVM(MP) increased by 15–35% and 21–29%, respectively. The water stability of RHVM(DP) asphalt mixtures was better than that of RHVM(WP) when the mixing time reached 180 s. RHVM(WP) asphalt mixtures have superior low-temperature cracking resistance, comparable water stability, and slightly poorer high-temperature stability than that of TPS(WP) asphalt mixture. Microscopic morphology observation found that some modifier particles and asphalt binder did not realize effective mixing under the DP and MP, and infrared spectroscopy results confirmed that TPS modifiers are mainly physically co-mingled with asphalt, while the tackifier resin in the RHVM reacts with the asphalt to form new functional groups to increase the viscosity of the asphalt.

Rheology of Crumb Rubber-Modified Warm Mix Asphalt (WMA).

This study explores the impact of adding waste vehicular crumb rubber to the commercially available warm mix additives Sasobit® and Zycotherm® on modified asphalt binders' physical and rheological properties. Various concentrations of crumb rubber (0%, 10%, 15%, and 20%) were introduced to asphalt binder samples with 2% and 4% Sasobit and 1.5% and 3% Zycotherm. The investigation employed conventional tests (penetration and softening point) and advanced mechanical characterization tests, including Superpave rotational viscosity (RV), Dynamic Shear Rheometer (DSR), DSR multi-stress creep recovery (MSCR), DSR linear amplitude sweep (LAS), and Bending Beam Rheometer (BBR). Traditional tests measured the asphalt consistency, while workability was assessed through the RV test. The results showed that the Zycotherm binders experienced a more significant penetration reduction than the Sasobit binders. Additionally, an increased crumb rubber content consistently elevated the softening point and rotational viscosity, enhancing the complex shear modulus (G*) values. Rubberized binders exhibited an improved rutting performance and low-temperature PG grades. Increasing the crumb rubber content enhanced fatigue life, with Z1.5CR20 and S2CR20 demonstrating the longest fatigue lives among the Zycotherm and Sasobit binders, respectively. Overall, Z1.5CR20 is recommended for colder climates, while S2CR20 is suitable for hot-climate applications based on extensive analysis.

Rheological Performance Analysis of Different Preventive Maintenance Materials in Porous High-Viscosity Asphalt Pavements.

Porous asphalt pavements are widely used in rainy and wet areas for their skid resistance, noise reduction, runoff minimization and environmental sustainability. Long-term moisture vapor erosion and the destabilization of large pore structures can easily result in pavement problems such as fragmentation, spalling, cracking, and excessive permanent deformation. To this end, four different preventive maintenance materials, including the rejuvenation (RJ), cohesion reinforcement (CEM), polymerization reaction, and emulsified asphalt (EA) types, were selected in this paper to improve the high-viscosity porous asphalt pavement. The effects of the different preventive maintenance materials on the temperature sensitivity, rheological properties and fatigue performance of high-viscosity modified asphalt were evaluated through temperature sweep, frequency sweep, multi-stress creep recovery (MSCR), linear amplitude sweep (LAS), and bending beam rheometer (BBR) tests. The results showed that the four preventive maintenance materials exhibit different enhancement mechanisms and effects. RJ improves the fatigue properties, deformation resistance and low-temperature cracking resistance of aged asphalt by adding elastomeric components; CEM materials are more conducive to increasing the low-temperature crack resistance of aged asphalt; while GL1 and EA improve the viscoelastic behavior of aged asphalt, but the effect of the dosing ratio needs to be considered.

Full-scale experimental investigation on the performance of seamless asphalt plug joint through mixture design and structural enhancements

The seamless asphalt plug expansion joint integrates a traditional asphalt plug joint (APJ) with an overlying continuous asphalt concrete layer, preventing block failure of the asphalt plug joint and enhancing driving comfort. However, typical damages such as fatigue cracking, rutting, and permanent deformation often occur in the upper asphalt layer. This is attributed to the inadequate stiffness of the lower joint plug mastic, particularly under high temperatures and heavy loads. To extend the service life of asphalt plug expansion joints under such conditions and enhance their durability, efforts were made to bolster the performance of the lower asphalt plug joint mixture and improve anti-rutting performance. This study involved: (1) Qualifying APJ mixture requirements under high temperature and heavy load by focusing on two critical material properties: good rutting resistance and permanent deformation resistance. High temperature rheological properties of these binders were examined through temperature scanning tests and multi-stress creep recovery tests (MSCR). (2) Exploring the impact of binder-aggregate ratios and specimen molding methods (standard compaction, paving vibration and pre-mixing) on the bonding strength and rutting resistance of the APJ mixture. This analysis was conducted using pull-off tests and dynamic stability tests. (3) Development of a novel APJ featuring dowel bars to enhance vertical deflection resistance and joint horizontal movement. Comprehensive laboratory tests showcased the modified joint structure's resilience after numerous test cycles, demonstrating exceptional resistance to bending and vertical deformation. The significant findings from this research provide valuable insights for optimal material selection, appropriate joint design, and installation guidelines for seamless asphalt plug expansion joints.

Evaluation of the Thermal Stability and Micro-Modification Mechanism of SBR/PP-Modified Asphalt.

To evaluate the thermal stability of composite polymer-modified asphalt, thermoplastic elastomer styrene-butadiene rubber (SBR)/polypropylene (PP) pellets were prepared using a hot-melt blending technique, with butyl rubber powder and waste polypropylene pellets as raw materials. The effects of different evaluation indexes on the thermal stability of SBR/PP-modified asphalt were investigated using a frequency scan test and a multi-stress creep recovery (MSCR) test, and the compatibility of SBR/PP particles with asphalt was studied using the Cole-Cole diagram and microstructure images. The tests show that, firstly, the performance grade (PG) classification of asphalt can be improved by adding an SBR/PP thermoplastic elastomer to enhance the adaptability of asphalt in high- and low-temperature environments, and the evaluation separation index can reflect the high-temperature storage stability of composite-modified asphalt more reasonably. Additionally, the larger the rubber-to-plastic ratio the worse the high-temperature thermal stability of composite-modified asphalt. Moreover, the addition of additives to the composite particles can promote the SBR/PP particles in the asphalt to be more uniformly dispersed, forming a more desirable microstructure and improving the thermal stability of composite-modified asphalt. Ultimately, the semicircular curve of the Cole-Cole diagram can reflect the compatibility characteristics of the two-phase structure of SBR/PP-modified asphalt, which can be used as an auxiliary index to evaluate the compatibility of polymer-modified asphalt.

Performance evaluation of styreneic methyl copolymer regenerated SBS-modified asphalt and its mixture with high content RAP

The aging degree of reclaimed asphalt pavement (RAP) is complex and diverse, and the current utilization rate of RAP is far from meeting the needs of green cycle development. To explore the effect of Styreneic Methyl Copolymer (SMC) rejuvenator of aging asphalt and the performance of SMC regenerated asphalt mixture containing 50% and 60% RAP, this study used SMC rejuvenator to regenerate SBS-modified asphalt with different aging degrees. The high and low-temperature rheological properties of regenerated asphalt were evaluated by temperature sweep test, multi stress creep recovery test, and bending beam rheometer test. Then, the recommended content of the SMC rejuvenator was obtained by using Matlab to establish the corresponding model. Finally, the road performance of the regenerated mixture with high-content RAP was verified. The test results showed that the recommended content range of the SMC rejuvenator for the aging asphalt with PAV (Pressurized Aging Vessel) 0 h, PAV5h, PAV10h, PAV15h, PAV20h were 1.56∼2.31%, 3.03∼3.36%, 4.269∼4.48%, 5.23∼5.66%, 5.95∼6.91%, respectively. The road performance of the SMC regenerated asphalt mixture with 50% and 60% RAP content met the specification requirements. SMC rejuvenator had no significant negative impact on high-temperature performance, significantly improving low-temperature cracking resistance. SMC regenerator had a positive significance in improving regeneration efficiency.

The Properties of Modified Bagasse Fiber/Nano-TiO2 Composite Asphalt in a High-Temperature and High-Humidity Salt Environment.

The southern tropical coastal areas of China are high-temperature and high-humidity salt environments, which hinder the durability and service life of ordinary asphalt pavement. To enhance the durability of asphalt pavement in these areas, modified bagasse fiber combined with nano-TiO2 was used to improve the corrosion resistance of asphalt pavement in high-temperature and high-humidity salt environments. The micro-morphology, high-temperature oil absorption, high-temperature heat resistance, and hygroscopicity of bagasse fiber modified using three silane coupling agents combined with NaOH were compared, and the best silane coupling agent/NaOH modification scheme for bagasse fiber was found. Based on conventional physical tests (penetration, softening point, ductility), rheological property tests (rotational viscosity, dynamic shear rheological test, multi-stress creep recovery test, linear amplitude scanning test), and a four-point bending fatigue test of the asphalt mixture, the properties of modified bagasse fiber asphalt binder and mixture after cyclic dry-wet erosion under pure water and salt solution (NaCl, Na2SO4) were determined, and the effects of the erosion environment and fiber ratio on the basic physical and rheological properties of the asphalt were clarified. Compared with the silane coupling agents KH550 and KH590, the bagasse fiber modified with KH570/NaOH had a better high-temperature oil absorption capacity, heat stability capacity, and matrix asphalt compatibility. The worst erosion environment was Na2SO4, but the increase in test temperature and fiber content weakened the sensitivity of the asphalt binder performance in different erosion environments. The erosion capacity order was as follows: Na2SO4 > NaCl > pure water. In the worst erosion environment, 0.5% modified bagasse fiber/Nano-TiO2 asphalt binder (Bn-570-0.5) had the best corrosion resistance in a high-temperature and high-humidity salt environment. The penetration, softening point, creep recovery rate R3.2, non-recoverable creep compliance Jnr3.2, and fatigue life after long-term aging (with 5% strain) of Bn-570-0.5 were, respectively, increased by -16.9%, 37.5%, 37.95%, -27.86%, and 38.30% compared with unblended base asphalt binder (B). In addition, the four-point flexural fatigue life of Bn-570-0.5 was 169.2% higher than that of the unblended base mixture.

Study on Aging Mechanism and High-Temperature Rheological Properties of Low-Grade Hard Asphalt.

In order to investigate the potential application of low-grade hard asphalt in high-temperature and high-altitude areas, various tests were conducted to analyze the performance and high-temperature rheological properties of 30#, 50#, and 70# matrix asphalt under thermo-oxidative aging and ultraviolet aging. The tests utilized for analysis included the examination of basic asphalt properties, Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), gel permeation chromatography (GPC), dynamic shear rheology (DSR), and multi-stress creep recovery (MSCR). The results indicate a progressive decrease in asphalt performance with increasing aging time. Prolonged exposure to thermal oxygen aging and ultraviolet irradiation significantly diminishes the plasticity of asphalt. The carbonyl index and sulfoxide index of asphalt increase after thermal oxygen aging and ultraviolet aging. Notably, 30# asphalt demonstrates greater resistance to aging compared to 50# and 70# asphalt under long-term high ultraviolet radiation. The LMS% of 30#, 50#, and 70# asphalt increases by 14%, 15%, and 16%, respectively. Following photothermal oxidative aging, a larger proportion of lighter components in the asphalt transforms into resins and asphaltenes. The high-temperature rheological properties of the three types of asphalt rank as 30# > 50# > 70#, while within the same type of asphalt, the high-temperature rheological properties rank as PAV > UV3 > UV2 > UV1 > RTFOT > virgin. Elevating temperature, stress level, and stress duration negatively impact the high-temperature stability of asphalt. In general, low-grade asphalt demonstrates superior anti-aging ability and high-temperature rheological properties during the aging process.

A Comparative Study for Creep and Recovery Behavior Characterization of Modified Bitumens Using the MSCR Test

In recent decades, the application of modified bitumens has experienced tremendous growth. However, due to the varying modification mechanism of different modifiers, the creep and recovery properties of modified bitumen have not been comprehensively understood. This study aims to evaluate the creep and recovery properties of several representative modified bitumens using the multi-stress creep recovery (MSCR) test. The MSCR test can highlight the unique delayed elasticity of modified bitumen and it uses a high stress level, which is more comparable to the field. In particular, this test also aims to identify the effects of different aging conditions. To do so, a total of 15 bitumens, including 7 elastomeric-modified bitumens, 5 non-elastomeric-modified bitumens, and 3 plain bitumens, were prepared and examined. Furthermore, 10 different aging conditions were considered. The results suggest that the generation mechanism of elasticity varies for different modified bitumens. There are two types of elasticities, which are energy elasticity and entropy elasticity, and their differences need more attention in the road bitumen material community. Aging changes the percentages of contributions from energy elasticity and entropy elasticity to the bitumen’s overall recovery performance. The increase in “bad” energy elasticity may compensate for part of the “good” entropy elasticity loss, but overall, the bitumen’s recovery rate is decreasing and the ratio of energy elasticity is increasing, which might hinder the bitumen’s road performance.

Effects of using waste solid sheet photopolymer plates in combination with SBS on the rheological properties of bitumen

ABSTRACT Large quantities of Solid Sheet Photopolymer plates (SSP) are used and wasted by the flexographic printing industry worldwide. The use of waste SSP, contains valuable polymers for bitumen modification, is an effective way of disposing of post-consumer products and an alternative way of obtaining new modifiers with good properties. Styrene–butadiene-styrene (SBS) copolymer, which is widely used in bitumen modification, causes excessive costs. The purpose of this study is to look at the effects of using SSP in combination with SBS and how much SSP saves on SBS content. Dynamic Shear Rheometer (DSR), Multi-Stress Creep Recovery (MSCR), Bending Beam Rheometer (BBR), Storage Stability tests, thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR) were carried out. The performance of the 4 and 5 wt.% single SBS modifications was compared with the SBS + SSP combination. SBS and SSP additives were found to interact well, and the use of 7% SSP in combination with 2% SBS provided improved low and high temperature performance and storage stability compared to the single 5% SBS modification. The use of waste SSP, which is cheaper than bitumen, together with SBS in bitumen modification offers a cost-effective and environmentally friendly solution without compromising performance.

Synergic effects between vacuum residue and polymers for preparing high-performance bitumens

This research presents a laboratory study on a polymer-modified bitumens (PMBs) made with a vacuum residue (VR) as a bitumen extender. Two different PMBs were prepared, one with a plastomeric Elvaloy and the other one with an elastomeric styrene-butadiene-styrene SBS. The mechanical properties of the samples were determined by means Multi Stress Creep Recovery tests (MSCR) and temperature sweep test. The results show that polymers can improve the mechanical properties of bitumen, and the vacuum residue can be used as softening bitumen extender. However, their simultaneous presence highlights non-additive effects giving optimal mechanical properties with a lowered temperature dependence of the viscoelastic properties and a high extension of the usage temperature range. The peculiar effect of the combined action of polymers and vacuum residue was also confirmed by chemical-physical analyses. In fact, Atomic Force Microscopy (AFM) and Nuclear Magnetic Resonance (NMR) relaxometry have shown that vacuum residue and polymers are able to effectively interact with the inner structures of the bitumen to give enhanced performances, with an increased stability upon temperature changes.

Designing electrostatic synergistic nanohybrid interface layer in polyester fiber for asphalt binder modification

AbstractIn this study, a novel multiscale synergistic reinforced polyester fiber (PET) was prepared by a bionic coating and electrostatic synergism. The three‐dimensional (3D) interconnected structure was developed on the surface of PET by electrostatically synergistic hybridization of negatively charged 2D lamellar graphene oxide (GO) and positively charged 1D hollow tubular aminated halloysite nanotubes (HNT). These fibers were applied to prepare fiber incorporated styrene‐butadiene‐styrene modified asphalt (SBS@MA). X‐ray photoelectron spectroscopy, atomic force microscopy, and field emission scanning electron microscopy analyses revealed that the 3D interconnected highly rough structure was constructed on the fiber surface. The surface free energy and adhesion work at the fiber and asphalt were calculated from the contact angle tests, which showed that adhesion work of the modified fibers was improved by 30% compared with the original fibers, confirming the better adhesion performance of GO‐mHNT‐PET fibers with the asphalt. The improved mechanical and viscoelastic characteristics of the modified GO‐mHNT‐PET/SBS@MA were verified by dynamic shear rheometer, and multistress creep recovery tests. At 46°C, the complex modulus of 1.5% GO‐mHNT‐PET/SBS@MA was 31.02% higher compared with that of PET/SBS@MA. This study provides a promising strategy for the preparation of PET/SBS@MA materials with excellent mechanical properties and interfacial bonding.

Study of the Properties of Waterborne Epoxy Resin Emulsified Asphalt and Its Modification Mechanism

Waterborne epoxy resin (WER) emulsified asphalt (WEREA) has the advantages of high viscosity and strength of epoxy asphalt, as well as a simple construction process, so it is used widely in asphalt pavement maintenance and repair projects. This paper investigated the comprehensive properties, the microstructure, the modification mechanism, and the strength formation mechanism of WEREA. The results of bond strength tests, adhesion tests between emulsified asphalt and coarse aggregate, conventional performance tests, and multistress creep recovery (MSCR) tests showed that with the increase of WER content, the adhesive properties and creep recovery properties at high temperature of the WEREA gradually improved, and gradually became the properties of brittle materials. When the WER content was 15%, the irrecoverable creep compliance of the WEREA stabilized and it met heavy traffic demand. In addition, fluorescence microscopy (FM) and scanning electron microscopy (SEM) showed that WER changed from having an island structure to having an epoxy skeleton structure in the WEREA. The results of Fourier-transform infrared (FTIR) testing showed that during the modification of the emulsified asphalt by the WER, no new substances were generated, which indicated that the sample possessed the mechanism of intermolecular physical blending. The test results were used to analyze the strength formation process of WEREA, which provides theoretical guidance for other researchers to study WEREA.

Chemical inhibition of wax precipitation to improve cracking resistance of warm mix asphalts

In recent years, the wax-based warm mix additives are always doped into the asphalt to lower the construction temperatures, which can lead to the substantial energy savings and promote energy sustainability. However, few studies have considered the methods to inhibit the premature precipitation of wax-based warm mix additives in warm mix asphalt, which will deteriorate the cracking resistances of asphalt pavement. This paper introduced a new method from the essence of the phase separation between the wax-based warm mix additives and asphalt leading to the reduction of cracking resistance, which chemically inhibited the premature precipitation of common additives (linear aliphatic hydrocarbon (LAH), polyethylene (PE), fatty acid amides (FAA), and Fischer-Tropsch (F-T) waxes) by wax inhibitors (WIs) to improve the compatibility of additives, and the cracking resistances of warm mix asphalts with addition of WIs were also investigated through the multi-stress creep recovery (MSCR), linear amplitude sweep (LAS), dynamic mechanical analysis (DMA), and thermal fatigue tests. The results show that the wax precipitation temperature (WPT) of warm mix asphalt reduces with the addition of WIs to inhibit the precipitation of additives to improve the compatibility, and the wax inhibition efficiencies of WIs are better with the asphalt doped with short-chain additives at higher content. The WIs can provide the warm mix asphalt with the additional elasticity and decrease the dependency on the applied strain, which increases the high-temperature rutting and intermediate-temperature fatigue resistances. The cracking and thermal fatigue resistances of warm mix asphalt at the low temperature can also be improved after doping with WIs, which is leaded by the precipitation inhibition of additives. Therefore, it is promising to improve the cracking resistances of warm mix asphalts and develop a new energy-saving pavement by chemically inhibiting the precipitation of additives.

Reinforcement Effect of Different Fibers on Asphalt Mastic.

Fiber materials as an asphalt mixture additive and stabilizer can effectively improve the performance index of asphalt pavement. In this study, lignin and carbon fiber were used as modifiers to study their effects on the road performance of asphalt mastic. Based on the frequency sweep, linear amplitude sweep (LAS) and multi-stress creep recovery (MSCR) experiments were conducted to test the high-temperature rutting and medium-temperature fatigue resistance of asphalt mastic with different fiber incorporation and low-temperature performance tests based on bending beam rheometer (BBR). The results indicate that adding fibers increased the stiffness of the asphalt mastic, and the modification effect of lignin fibers was better than that of carbon fibers. Meanwhile, the characteristic flow index of the asphalt mastic gradually increased with the increase in temperature, indicating that it gradually became a near-Newtonian fluid at higher temperatures. The addition of fibers also improved the high temperature rutting resistance of the asphalt mastic but did not have an advantageous effect on fatigue and low temperature cracking resistance. Additionally, the fitting results of the four-parameter Burgers model show that the use of fiber modification decreases the proportion of elasticity and viscous creep compliance but increases the delayed elasticity part.

Effect of glutaraldehyde-chitosan crosslinked graphene oxide on high temperature properties of SBS modified asphalt

Composite material using glutaraldehyde (GA) cross-linked chitosan (CTS) and graphene oxide (GO-CTS-GA) was designed applying electrostatic interaction strategy under strong alkali environment. GO-CTS-GA was in turn applied to prepare styrene butadiene styrene (SBS) GO-CTS-GA/SBS composite modified asphalt (MA)_binder. The effect of GO-CTS-GA on the physical properties of SBS modified asphalt binder was investigated and its mechanism of action was analyzed. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and atomic force microscopy tests confirmed the retainment of GO flakes microscopic dimensions while compensating for the chemical structural defects and mechanical property damage of GO. The results of dynamic shear rheometer and multi-stress creep recovery tests indicated that the GO-CTS-GA/SBS-MA binder exhibited better viscosity performance and elasticity performance, rutting resistance and high temperature thermal stability. At 64 °C, the loss modulus of 0.10 % GO-CTS-GA/SBS-MA was 29.5 % and 25.2 % higher than that of SBS-MA and GO/SBS-MA, respectively. SEM and TEM analyses of the four components of asphalt binder before and after modification revealed that the change of asphaltene microscopic morphology seriously affects the stability of asphalt colloidal system. Fourier transform infra-red analysis of the MA binder revealed that the change of saturation fraction and colloidal polarity by GO-CTS-GA is responsible for the dispersion and cross-linking of SBS chain segments in the asphalt binder phase. This study provides important reference information for nanomaterials to change the macroscopic mechanical properties by modulating the microstructure, physical and chemical properties of asphalt binder at the micro and nano-scale.