Low-temperature Cracking Resistance Research Articles

Laboratory performance and construction challenges for plant produced asphalt mixes containing RAP and RAS

In this study, four plant-produced asphalt mixes were considered to evaluate the performance and construction challenges of mixes containing RAP/RAS. Also, asphalt mixes were collected at two different plant-production times for each mix type to monitor the performance variability between lots. A softer base binder (PG 58–22) was used for mixes with RAS compared to the base binder (PG 64–16) used for the control mix (no RAP or RAS) and the mix with only RAP. Use of small dosages of rejuvenators and the softer binder in the RAS mixes were found to show similar performance compared to the control mix with no RAP or RAS. The results obtained from the extracted binders of these mixes indicate that mixes with RAP and RAP/RAS are expected to show higher rutting resistance and slightly lower low-temperature cracking resistance, also shown in the mix rutting and fracture cracking tests. A similar fatigue life was observed for all mixes at low strain levels in the Four-Point Beam test. However, the mix with both RAP and RAS was found to show better fatigue life at high strain levels. Similar performance test results were observed between different lots of the same mix type for most cases. Finally, there were no problems with field mixing, compaction, or finishing of the mixes containing RAP and RAP/RAS.

Microwave Heating Healing of Asphalt Mixture with Coal Gangue Powder and Basalt Aggregate

Microwave heating is an effective method to achieve autonomic crack healing in asphalt mixtures, and the use of microwave-absorbing materials can largely improve this healing efficiency. As a solid waste, coal gangue contains metal oxides, which shows the possibility of microwave heating. In order to further promote the application of coal gangue in the microwave healing of asphalt mixtures, this study looks into the synergistic effect of basalt and coal gangue powder (CGP) on the microwave heating self-healing of an asphalt mixture. The mechanical performance, water stability, low-temperature crack resistance and microwave healing efficiency of the asphalt mixture were investigated using the immersion Marshall test, standard Marshall test, Cantabro test and semi-circular bending (SCB), and healing tests, respectively. The results indicated that the addition of CGP in asphalt mixture can improve the microwave heating speed, which also showed a significant advantage in water stability and fracture energy recovery. The research results will further promote the utilization rate of coal gangue.

Investigation on performance and durability of bone glue and crumb rubber compound modified asphalt and its mixture

Rubberized asphalt has excellent environmental protection and road property, but its storage stability needs improvement. Existing studies have found that the compound modification of bone glue (BG) and crumb rubber (CR) can effectively raise the separation of CR in asphalt, along with outstanding comprehensive properties. Therefore, this paper explores the micro mechanism, aging performance, and engineering characteristics of bone glue and crumb rubber compound modified asphalt (BCCMA). First, the adhesion of BCCMA was evaluated by a static drop test, and a scanning electron microscope test revealed its microscopic surface morphology. Second, three aging indices using rheological tests were developed to evaluate the aging resistance ability of the BCCMA. Lastly, the road performance of the bone glue and crumb rubber compound modified asphalt mixture (BCCMAM) was investigated. The results indicate that the surface energy of BCCMA (15% BG and 20% CR) increased by 52.39% compared to the neat asphalt. BG can improve asphalt's aging resistance, and the BCCMA with a BG content of 10% has the lowest aging sensitivity. BG promotes the dispersion uniformity of CR in neat asphalt, making the low-temperature crack resistance, high-temperature stability, and water stability of BCCMAM better than rubberized asphalt mixture.

Modification and Enhancing Contribution of Fiber to Asphalt Binders and Their Corresponding Mixtures: A Study of Viscoelastic Properties.

The performance of asphalt binders and asphalt mixtures can be enhanced by the inclusion of fiber. The viscoelastic characteristics of fiber-reinforced asphalt binders and their corresponding mixtures were characterized in this study. To generate fiber-reinforced asphalt samples for dynamic shear rheometer (DSR) tests, polypropylene fibers (PPFs), polyester fibers (PFs), and lignin fibers (LFs) were added into modified asphalt with a ratio of 5wt%. Indirect tensile resilience tests were conducted on the fiber-reinforced asphalt mixture with Marshall samples, which was prepared with a 6.4% of bitumen/aggregate ratio. The addition of fiber can increase the anti-rutting performance of asphalt binders, and also reduce the anti-fatigue performance of asphalt binders to varying degrees. Viscoelastic properties of the fiber-reinforced asphalt binders are highly dependent on the shape of the used fiber. The resistance of the fiber-reinforced asphalt binders to rutting at high temperatures increases with the roughness degree of the fiber's surface morphology. PPF-reinforced asphalt binders surpass the others in terms of anti-rutting capabilities. The high-temperature deformation resistance of the PPF-reinforced asphalt mixture is stronger, whereas the low-temperature crack resistance of the PF-reinforced asphalt mixture is stronger, which can be observed from the master curve of indirect tensile resilient modulus.

Design and performance evaluation of a new green pavement: 100% recycled asphalt pavement and 100% industrial solid waste

In order to achieve sustainable development of road construction while addressing the occupation of land resources and the environmental impact of recycled asphalt pavement (RAP) and industrial solid waste, as well as the problem of insufficient resistance to permanent deformation and durability of conventional asphalt pavement, this study designed a new type of green pavement, which uses 100% RAP to form a large void matrix skeleton and 100% solid waste to prepare grouting materials. Research has found that green pavement has significantly higher high-temperature stability and durability than conventional asphalt pavement. The green pavement formed with a continuous gradation RAP matrix skeleton can be 100%–1000% higher than the green pavement formed with a single particle size gradation RAP matrix skeleton under the same fatigue stress ratio and load. At the same time, it also has significantly higher low-temperature bending characteristics, strength characteristics, and crack resistance. The above indicates that the green pavement designed in this study has good pavement performance, mechanical properties, and durability, especially the green pavement formed with a continuous gradation RAP matrix skeleton.

Laboratory investigation of the impact of peanut husk ash as an asphalt binder modifier on physical and rheological properties

Researchers propose using agricultural waste into asphalt pavements as a means to raise recycling rate of waste, conserve natural resources, and reduce disposal issues. This paper was set out to explore the ability of peanut husk ash (PHA) as an asphalt binder modifier. To this end, scanning electron microscope (SEM), softening point, penetration, ductility, storage stability, rotational viscosity, multiple stress creep recovery (MSCR), temperature sweep, frequency sweep, and bending beam rheometer (BBR) tests were applied. Besides, the temperature susceptibility was evaluated using the penetration index, while the fatigue parameter was applied to assess the intermediate temperature performance of asphalt binder. Moreover, the response surface methodology (RSM) was performed to assess the interactive impact of load frequency, temperature, and PHA concentrations on the rutting factor and complex modulus, besides the interaction between them. Moreover, models were proposed to fit the findings of experimental work to predict the responses. The findings manifested that asphalt binder can be modified with 8% or less of PHA without experiencing phase separation issues during high temperature storage. Furthermore, the SEM demonstrated that PHA was well dispersed in the modified asphalt. Moreover, the increment of PHA led to increase penetration index, softening point, viscosity, rutting parameter, percent recovery, and complex shear modulus, as well as reducing nonrecoverable creep compliance (Jnr), phase angle, penetration, and ductility. Although the high temperature performance was enhanced, there was a decrease in fatigue and low temperature cracking resistance. The RSM analysis revealed that the input factors significantly affected the asphalt's rutting factor, and complex modulus, and quadratic models were suggested to predict the potential for rutting.

Effect of Blending Behavior on the Performance of Hot Recycled Asphalt Mixtures

Blending behavior is the main factor influencing hot recycled asphalt mixtures’ actual and design performance. The following steps were taken to investigate the above issues. Firstly, the component changes of asphalt mixtures were studied by thin-layer chromatography, with flame ionization detection to obtain the mechanism of asphalt aging and recycling. Secondly, according to the difference in the recycled asphalt components, the hot recycled asphalt mixtures were optimized based on the Marshall design method. Lastly, the hot recycled asphalt mixtures for the three mixing processes were prepared using the optimized design method described above. Laboratory tests were conducted to evaluate the correlation between the degree of blending (DoB) and the high-temperature stability, low-temperature crack resistance, water stability, and fatigue performance. The test results indicate that reducing light components (saturates and aromatics) and increasing heavy components (asphaltenes and resins) are the main reasons for asphalt aging, and asphalt recycling is an inverse process. Additionally, the performance of hot recycled asphalt mixtures is improved with an increase in DoB. Specifically, the DoB is only 50% to 60% under a normal mixing process, but by adjusting parameters the DoB will increase to 80% to 90%.

Improving rheological and thermal performance of Gilsonite-Modified binder with phase change materials

Gilsonite, as a type of natural asphalt binder, has been used to improve the high-temperature performance of regular asphalt binders. However, the addition of gilsonite may compromise binders’ low-temperature thermal cracking resistance. In this research, polyethylene glycol (PEG), as one type of the phase change materials (PCMs), was used as an innovative material to balance the impacts of gilsonite on high and low performance of asphalt binders. The dosages of gilsonite and PEG were first determined based on the materials’ rheological behaviors at low temperatures. The performance of the PEG-gilsonite-modified binder was then fully evaluated in terms of the resistance to cracking and rutting at various temperatures. Thermal tests were also conducted to assess the thermal behaviors of the modified binders. The testing results indicate that with the proper dosage of gilsonite and PEG, the rutting resistance of the binder can be improved without sacrificing its low-temperature performance. With the addition of the PCM, the binder was tested to have high volumetric heat capacity, which indicates PCM can reduce the rate and the magnitude of the temperature changes in pavements.

Rheological properties and viscosity reduction mechanism of aromatic/naphthenic oil pre-swelling crumb rubber modified asphalt

Using light oil to pretreat the crumb rubber (CR) could reduce the viscosity of the modified asphalt, thereby enhancing its compatibility with asphalt binder and improving the workability of CR modified asphalt (CRMA). However, the effects of CR pre-swelling on rheological properties of CRMA and the viscosity reduction mechanism are not well understood, especially for commonly used aromatic and naphthenic oils. In this study, the comparative investigations on rheological properties of CRMA before and after pre-swelling process were performed by frequency sweep, temperature sweep, multiple stress creep and recovery (MSCR) and storage stability tests. Meanwhile, the molecular dynamic (MD) simulation method was applied to simulate the distribution, migration, and aggregation characteristics of aromatic oil, naphthenic oil, and asphalt components in CRMA from natural aggregation state to heating mixing and finally cooling, aiming to reveal the viscosity reduction mechanism. The results showed that aromatic and naphthenic oils can significantly reduce the viscosity of CRMA. In addition, the low-temperature crack resistance and storage stability of CRMA can be improved through pretreatment with aromatic and naphthenic oils, which is correlated with the oil content. However, the effects of aromatic and naphthenic oils pre-swelling processes on the high temperature properties of CRMA are different. The MD simulation results showed that the binding energy between asphalt molecules reduced after mixing with aromatic and naphthenic oils, which is which is the primary reason for the viscosity reduction of CRMA. However, there are differences regarding the distribution characteristics of these two oils within asphalt binder. The CR, aromatics, aromatic oil and resins were uniformly dispersed in CRMA system by aromatic oil, whereas the naphthenic oil was adsorbed onto the surface of CR and asphaltenes.

Interaction state and element leaching of waste incineration fly ash-asphalt mortar based on fillerization

Fly ash from diverse sources had various physical and chemical properties, resulting in different modified asphalt properties. Therefore, this paper aimed to investigate the interaction between fly ash and asphalt from different sources and the performance of fly ash-asphalt mortar and further sought the best-replaced amount of fly ash. The fillers included limestone, Dongguan fly ash, and Guangzhou fly ash. First, the filler's physical and chemical properties and microstructure were evaluated. Secondly, asphalt mortar was prepared according to the replaced amount (0%, 25%, 50%, 75%, 100%) and powder binder ratio (0.7). Then, the basic performance test, micro test, high-temperature rheological test, and low-temperature rheological test were conducted on asphalt mortar to investigate the interaction between fly ash and asphalt, as well as the high-temperature performance, elastic recovery ability, and low-temperature crack resistance of asphalt mortar. Finally, the segregation and heavy metal leaching of fly ash-asphalt mortar (FA-AM) were evaluated by the segregation and ICP test. The results indicate that fly ash had a small particle size, a rugged surface, well-developed porosity, abundant mineral components including potassium salt, sodium salt, and calcium carbonate, strong interaction with bitumen, and excellent compatibility. Adding fly ash and increasing the replacement amount improved the high-temperature performance of asphalt and enhanced the elastic recovery ability, but the low-temperature performance was weakened. The enhancement of Dongguan fly ash's high-temperature performance was more significant, while the low-temperature performance of Guangzhou fly ash was marginally superior to that of Dongguan fly ash. However, there was no discernible difference between the two types of fly ash in terms of elastic recovery ability. Segregation had no noticeable effect on the heavy metal absorption concentration of FA-AM, and the storage stability was excellent. Asphalt had the best stabilization effect on Zn, Cu, and Pb in FA-AM (Dongguan) and Pb and Cr in FA-AM (Guangzhou). The recommended replacement amount of Dongguan fly ash and Guangzhou fly ash was 25%∼50%.

Experimental Study of Permeable Asphalt Mixture Containing Reclaimed Asphalt Pavement

The current focus of research attention on reclaimed asphalt pavement (RAP) utilization is expanding the applications of RAP. This study aims to analyze the road performance of recycled permeable asphalt mixtures (RPAMs), which represents a novel direction for utilizing RAP. Firstly, the Marshall design method was used to carry out the material composition design of the RPAM with varying RAP contents (10%, 20%, and 30%). Subsequently, the performance of the RPAM with different RAP contents (10%, 20%, and 30%) and preheating temperatures (120 °C, 130 °C, 140 °C, 150 °C, and 160 °C) was tested with a permeable asphalt mixture containing 12% high-viscosity asphalt as the control group. The mixture’s performance included high-temperature stability, low-temperature crack resistance, water stability, anti-raveling performance, and dynamic mechanical properties. The results indicate that the higher the RAP content, the better the high-temperature performance of the RPAM, while the low-temperature performance, water stability, and anti-raveling performance deteriorate. At 30% RAP content, its pavement performance is comparable to that of the control group mixture. However, increasing RAP preheating temperature can improve low-temperature and water stability but may reduce high-temperature performance. The optimal RAP preheating temperature for pavement performance is between 140 and 150 °C. The dynamic modulus test showed that the higher the RAP content, the greater the dynamic modulus of the RPAM, leading to better high-temperature stability but reduced low-temperature crack resistance. The influence of RAP preheating temperature is the opposite. These test results demonstrate the feasibility of utilizing RAP for paving permeable asphalt pavement under controlled RAP content and preheating temperature conditions.

Another look at the semi-circular bend test for the performance ranking of hot mix asphalt

Semi-circular bend (SCB) testing has been widely used to evaluate the cracking resistance of asphalt mixtures. However, it remains unresolved which of the various SCB protocols can provide the most sensitive and precise ranking of different asphalt mixtures. This study aims to improve the current SCB protocol, emphasizing mixture preparation, testing condition and evaluation indices. The effect of aging methods in terms of reversible aging and irreversible aging and loading rates on the intermediate and low temperature cracking resistance of asphalt mixtures was analyzed. Subsequently, the response of different cracking evaluation indices was analyzed. Finally, the repeatability of different cracking evaluation indices was discussed. The results show that higher loading rates are slightly more sensitive to mix composition, possibly due to the toughening effect of polymer modifiers. However, whether higher or lower rates are more accurate remains to be investigated with ongoing field studies. Cracking initiation and resistance indices (CII and CRI) were superior from a repeatability and dynamic range perspective in comparison to flexibility and balanced cracking indices (FI and BCI). Thermoreversible aging over three days of cold conditioning at − 20 °C was found to significantly affect binder properties in selected samples. However, none of the SCB parameters after testing appropriately cold conditioned samples at room temperature reflected this deterioration. Hence, it remains to be investigated whether mixture testing at ambient temperatures properly ranks superior quality Alberta, Canada and Venezuelan sourced materials that are low in wax.

Performance Improvement of Asphalt Mastics Using Bamboo Fiber Reinforcement

Integrating fibers into asphalt mixtures improves their crack resistance and permanent deformation. Previous studies have found the effect of various fibers on asphalt mixtures, but bamboo fibers were not included. In addition to providing strength and toughness, bamboo fiber’s recycled nature saves resources and protects the environment. This study investigates the reinforcement effect by different particle sizes and contents of bamboo fiber on asphalt mastic. Three sizes (100 mesh, 200 mesh, and 400 mesh) and three contents (3%, 6%, and 9%) of bamboo fibers were selected to modify the asphalt mastic. The frequency sweep (FS), linear amplitude sweep (LAS), multiple stress creep recovery (MSCR), and bending beam rheometer (BBR) test were used to evaluate the linear viscoelastic properties, fatigue performance, rutting resistance, and cracking resistance of fiber-modified asphalt mastics, respectively. Results demonstrate that bamboo fibers have excellent stiffness-reinforced characteristics, increase the elasticity of the asphalt, and enhance the high-temperature stability and low-temperature crack resistance of the asphalt mastic but adversely affect the fatigue properties of the asphalt mastic. In addition, asphalt mastics exhibited the same crack initiation stage and different crack expansion behavior, and the fiber incorporation prevented further crack propagation. Burgers model was used to represent the rheological behaviors of the asphalt mastic with bamboo fiber, and the model parameters are estimated. Furthermore, the Burgers model results indicated that the fiber addition reduced the proportion of elastic compliance and viscous compliance but increased the proportion of delayed elastic compliance of the asphalt mastic. Finally, the statistical model obtained based on the statistical approach can appropriately fit the values of rheological parameters with different fiber contents and lengths. The optimal design solution is 200 mesh with 9% content.

Laboratory evaluation of the performance of reclaimed asphalt mixed with composite crumb rubber-modified asphalt: reconciling relatively high content of RAP and virgin asphalt

ABSTRACT Reclaimed asphalt pavement (RAP) applications are largely limited by the insufficient performance of reclaimed asphalt (RA). To address this challenge, the composite crumb rubber-modified asphalt (CCRMA) with SBS and SBR modifiers was mixed with RA to prepare reconciling and reclaimed modified asphalt (RRMA) and evaluate its performance in laboratory tests. Experimental groups of RRMA included five RA contents (30%, 40%, 50%, 60%, and 70%) and three aging degrees. Results showed that RRMA’s high-temperature and fatigue resistance performances improved by adding CCRMA, while this improvement was weakened with increasing RA content and aging degree. This was because the addition of CCRMA reduced the morphology of ‘bee-like structures’ and improved resistance to deformation. CCRMA slightly reduced moderate-temperature crack resistance but still improved low-temperature crack resistance because adding CCRMA reduced the internal adhesion of asphalt. The moderate-temperature crack resistance was below the threshold. However, it is necessary to consider adding other technical means when RRMA was aged for more than 20 hours with more than 60% RA content. Furthermore, the reliability of excellent performance was 85% for RRMA with 30% RA content under a short-term aging state, which provided a reference for the design of reclaimed asphalt binder.

Characterization of Sustainable Asphalt Binders Modified with Styrene–Isoprene–Styrene (SIS) and Processed Oil

The current study aims to evaluate the viscosity and rheological properties of PG 64-22 modified with Styrene–Isoprene–Styrene (SIS) and Processed Oil (PO) to enhance asphalt binder properties. Performance properties were measured at high, intermediate, and low temperatures. PG 64-22 was blended with SIS and Processed Oil at three levels (5%, 10%, and 15% by weight of binder) and two concentrations (6% and 12% by weight of binder), respectively. Modified binders underwent two short and long artificial aging processes, through the spinning of the thin film in an RTFO oven and a pressure aging vessel (PAV). The Superpave binder evaluations were carried out using a rotational viscometer (RV), dynamic shear rheometer (DSR), and bending beam rheometer (BBR). According to the findings of the research, the addition of SIS caused higher values of viscosity, but when co-modified with processed oil, there was a substantial decrease in viscosity values. As a result, workability was improved. (1) It was observed that a greater reduction in viscosity was achieved when the processed oil was present at a higher concentration at 135 °C compared to a lower concentration. (2) The study showed that the incorporation of processed oil led to a reduction in rutting performance of the asphalt binder. However, the addition of SIS resulted in a notable enhancement of rutting resistance. (3) The role of processed oil as co-modifier at concentrations of 6% and 12% caused significant decreases in G*sin δ, based on the susceptibility of asphalt molecules to accept oil molecules in their network links. (4) The extracted measurements from the BBR tests indicated that modification with SIS and PO improved the low-temperature cracking resistance significantly. Comparison of asphalt binders modified with 6% and 12% PO and the same SIS content showed significant changes in modification with 12% PO rather than 6%.

Rheological Properties of Composite Inorganic Micropowder Asphalt Mastic

Graphene Tourmaline Composite Micropowder (hereinafter referred to as GTCM) modified asphalt was prepared by the ball milling method. The effects of different temperatures and different frequencies on the high-temperature performance of composite-modified asphalt were evaluated by dynamic shear rheological test, and the viscoelastic properties of composite-modified asphalt under different stresses and different temperatures were analyzed. The low-temperature rheological properties of GTCM-modified asphalt were analyzed by bending beam rheological test, and its mechanism was analyzed by Fourier transform infrared spectroscopy (FTIR) test. The results show that the temperature sensitivity and anti-aging resistance of GTCM-modified asphalt are significantly higher than that of tourmaline-modified asphalt. The improvement effect gradually increases with the increase in graphene powder content, and its addition does not change the viscoelastic properties of asphalt. The complex shear modulus and phase angle of GTCM-modified asphalt at appropriate temperatures are more conducive to tourmaline-modified asphalt and matrix asphalt, which can improve the rutting resistance of asphalt. In the same type, with the increase in composite modified micropowder content, the rutting resistance of modified asphalt is better. The improvement of rutting resistance of GTCM-0.5, GTCM-1.0 and GTCM-1.5-modified asphalt can reach 12.95%, 10.12% and 24.25%, respectively; the improvement range is more complicated due to temperature and frequency changes. The GTCM-modified asphalt has good low-temperature crack resistance. The creep stiffness modulus of GTCM-modified asphalt decreases with the increase in load time under different types and dosages, and its stiffness modulus is smaller than that of tourmaline-modified asphalt and mineral powder asphalt mastic. The creep rate increases with the extension of load time, which is greater than that of tourmaline-modified asphalt and mineral powder asphalt mastic. When the load was 60 s, the creep stiffness modulus of GTCM-0.5, GTCM-1.0 and GTCM-1.5-modified asphalt decreased by 5.75%, 6.97% and 13.73%, respectively, and the creep rate increased by 1.37%, 2.52% and 4.35%, respectively. After adding GTCM or tourmaline to the matrix asphalt, no new functional groups were produced due to the chemical reaction with the asphalt.

Use of the Iron Chloride Type of Lewis Acid Catalyst in High Reclaimed Asphalt Pavement Content Asphalt Mixtures

The use of reclaimed asphalt pavement (RAP) as a partial replacement for virgin aggregates and asphalt binders has received considerable attention recently. This approach is one of many promising methods for improving sustainability. However, many state Departments of Transportation are cautious in adopting high RAP content into their designs because of cracking and durability issues resulting from the aged RAP binder. A Lewis acid catalyst has been used to modify the asphalt binder’s chemical composition and disrupt the associated molecules formed in the aged RAP binder. The objective of this study is to assess the effectiveness of the use of a Lewis acid catalyst in improving the cracking resistance of an asphalt mixture containing high RAP contents. A suite of laboratory mechanical tests was performed, namely, the dynamic modulus test for linear viscoelastic properties; the semi-circular bend, Illinois flexible index, ideal cracking tolerance, and simplified viscoelastic continuum damage tests for fracture and fatigue resistance; the loaded wheel tracking test for rutting resistance and moisture susceptibility; indirect tensile creep compliance and strength tests for low-temperature cracking resistance; and the Cantabro abrasion test for durability. Further, AASHTOWare Pavement ME software was used to predict the long-term performance of asphalt pavements containing mixtures with high RAP contents and a Lewis acid catalyst. Results showed that the use of the Lewis acid catalyst can disrupt associated molecules formed in the aged RAP binder. Thus, asphalt mixtures containing high RAP contents (recycled binder ratio > 0.20) and a Lewis acid catalyst exhibited similar performances to conventional mixtures. Further, Pavement ME predicted fatigue cracking was lower for a structure containing a FeCl3-modified mixture as compared to a similar one with no FeCl3, illustrating the effectiveness of FeCl3.

Experimental investigation of usability of modified asphalt binder with waste expanded polystyrene (EPS)

EPS (Expanded polystyrene) is widely used in construction and packaging industries. Unfortunately, EPS is not mostly recyclable because it might not be economically feasible to store, transport, and process EPS so that it becomes recyclable. Therefore, alternative waste management strategies are urgently needed. The main objective of this study is to experimentally investigate the potential use of waste EPS in asphalt binder modification. As part of this study, a base asphalt binder with a Penetration grade of 70/100 was modified with waste EPS in four different ratios (0%, 1.5%, 3% and 4.5%, by weight of asphalt binder). The modified asphalt binder specimens were tested based on several physical (penetration, ductility, softening points and viscosity) as well as rheological/Superpave binder grading system tests including Rolling Thin Film Oven (RTFO), Pressure Aging Vessel (PAV), Dynamic Shear Rheometer (DSR), and Bending Beam Rheometer (BBR). Based on the tests results, rheological and engineering properties of the modified asphalt binders were compared with the ones of the base binder so that effect of waste EPS addition on the properties of the base binder was evaluated; and how the Superpave binder grades of the modified binders were changed with the additions of waste EPS was discussed. It was found out that modifying asphalt binders with EPS provided them with a better rutting resistance at the expense of lowering their fatigue and low temperature cracking resistance. Overall, it could be concluded that waste EPS can be potentially used in the asphalt binder modification by paying special attention to these factors, and it should be noted that using waste EPS in the asphalt binder modification has many economic and environmental benefits.

Low-Temperature Crack Resistance of Basalt Fiber-Reinforced Phase-Change Asphalt Mixture Based on Digital-Image Correlation Technology

DaoLu Tiaowen Cailiao (DTC) phase-change materials are important materials for improving the temperature adaptation of asphalt pavements. In order to improve the low-temperature crack resistance of asphalt pavements after adding DTC phase-change materials, basalt fiber-reinforced DTC phase-change asphalt mixtures with different basalt fiber dosages were prepared, and their mechanical properties, horizontal strain, and crack characteristics were analyzed using semicircular bending tests combined with digital-image correlation technology. The study showed that the basalt fiber increased the fracture strength of the phase-change asphalt mixture, delayed its damage time, improved its deformation capacity, reduced the crack development rate and damage degree of the interface, and enhanced its low-temperature crack resistance. The enhancement of low-temperature crack resistance of phase-change asphalt mixtures increased and then decreased, and the best effect was achieved when the dosage of basalt fiber was 3‰, which delayed the damage time of phase-change asphalt mixtures by 42.53 s, slowed down the crack expansion rate by 54.23%, and reduced the fractal dimension (D) and damage factor (Df) by 4.32% and 29.83%, respectively. In conclusion, basalt fibers can enhance the low-temperature crack resistance of phase-change asphalt mixtures, and the optimal dosage of basalt fiber is 3‰. Also, both D and Df showed a positive correlation pattern with KIC, but Df was more closely related to KIC, which shows that the new index Df based on the image analysis method and MATLAB software is reliable.

Investigation of road performances of rejuvenated styrene-butadiene-styrene modified asphalt mixture

Exploring the effective recycling of waste styrene-butadiene-styrene block copolymer (SBS) modified asphalt mixture is the difficulty and hotspot in the field of road materials research. Common rejuvenation method and reactive rejuvenation method were used to recover the road performances of aged SBS modified asphalt mixture (ASMBM) in this paper. The recovery effect of high- and low-temperature performance, fatigue resistance and water stability for ASMBM after rejuvenation was studied, and the road performance development of ASMBM after reactive rejuvenation in the early stage was also investigated. The results show that reactive rejuvenation method could significantly enhance the Marshall stability and rutting resistance of rejuvenated ASMBM, and further improve its low-temperature cracking resistance as compared with common rejuvenation method, which attributes to the reconstruction of aged SBS cross-linking structure and its improvement on the interface stability of rejuvenated mixture. Meanwhile, the fatigue life of reactive rejuvenated ASMBM under strain level of 400 με is 26.6 % higher than that of common rejuvenated mixture. Water stability test results show that reactive rejuvenation is more beneficial to restore the water-immersed Marshall stability and Hamburger rutting resistance of ASMBM. Furthermore, the road performances of reactive rejuvenated ASMBM have a further improvement with the extension of time in the early stage after rejuvenation, its Marshall stability, the freeze-thaw splitting strength ratio and water-immersed Marshall stability could restore to the initial level of fresh mixture. Thus, reactive rejuvenation method is more conducive to realizing the high-performance recycling of waste SBS modified asphalt mixture and enhance its recycling value.