High-viscosity Asphalt Research Articles

Utilization of thermoplastic resin as foamed asphalt modifier in cold recycled mixtures

The utilization of foamed virgin asphalt in cold recycled mixtures results in insufficient bonding strength between aggregates, leading to rapid deterioration to the recycled asphalt pavement. This ultimately causes inefficient clean production and increased carbon emissions. The foaming performance of thermoplastic resin modified asphalt (TRA) under different foaming conditions was analyzed. Micro-scale chemical and physical tests were utilized to discover the foaming mechanism of TRA. The road performance of cold recycled mixtures with foamed TRA was evaluated through splitting, rutting and fatigue tests. The results showed that the increase in the TRA polar functional group index led to an increase in its surface tension, thus limiting its expansion capacity. However, the increase in the specific heat capacity of TRA indicated that it preserves a low viscosity level essential for its foaming efficacy post-ejection from the foaming machine, thereby enhancing its half-life. Furthermore, the dynamic viscosity of the TRA with an 8% thermoplastic resin dosage exceeded 40000 Pa s at 60 °C, meeting the specification requirements for high viscosity asphalt, while exhibiting a notably lower viscosity of only 120 mPa s at the foaming temperature of 170 °C. The observed low viscosity of the asphalt is anticipated to favorably enhance the formation of a stable foam structure. The mechanical properties and overall road performance of the cold recycled mixture with foamed TRA were significantly enhanced, especially in terms of moisture damage resistance and low-temperature crack resistance. The purpose of this paper is to serve as a valuable reference for investigating the mechanism of modified asphalt foaming and to enhance the efficiency of cold recycled pavement regeneration processes.

Interfacial adhesion features of high-viscosity asphalt and aggregate under water conditioning: Micro perspective and molecular simulation

Interface properties between asphalt and aggregate intimately affect the service performance and long-term durability of asphalt pavement. This study seeks to explore the interfacial adhesion features of high-viscosity asphalt (HVA)-aggregate under water conditioning to provide the understanding for the moisture damage of HVA-aggregate interface and asphalt pavement. To this end, the HVA was initially suffered from different durations of water conditioning, and atomic force microscopy (AFM) test was employed to gather the microscopic phase structure and adhesion force of water-conditioned HVA and aggregate, to analyze the adhesion variations of HVA-aggregate interface. Further, molecular dynamics method was used to simulate the changing process and influencing mechanism of adhesion effect at the HVA-aggregate interface under water immersion. The findings indicated that with the increasing water immersion, Catana phase of HVAs vanished, and concave and convex structures appeared on the surface, along with pit groove dispersion phase structures. Longer immersion time resulted in augmented surface roughness of HVA and a more dispersed height distribution in the area domain, most notably during the initial stages of water immersion. Aging increased sensitivity to immersion duration in terms of surface roughness, mechanical properties and adhesion ability of HVAs. Water immersion had a diminishing effect on the mechanical properties of HVA at different aging degrees, although it increased the micro-mechanical modulus of HVAs and impaired the interface adhesion with aggregates. Under water immersion, the phase structure and mechanical properties of HVAs and the interface adhesion indexes all distinguished a prominent negative Pearson correlation (correlation coefficient |R| > 0.7000), and these factors were critical for HVA-aggregate interface adhesion, as alterations in surface phase structure and micro-mechanical traits of HVAs triggered variations in the HVA-aggregate interface adhesion. In addition, water content in the interface layer, simulation temperature and mineral anisotropy significantly affected the interfacial adhesion of HVA and aggregate in water environment. The introduction of water and the rise of temperature considerably weakened the interfacial adhesion effect of asphalt-aggregate system, and the interface adhesion failure occurred once the water layer thickness surpassed 5 Å. Comparatively, the HVA-calcite system demonstrated better interfacial adhesion competence than the HVA-α-quartz system, and the HVA-calcite {1 0 4} system showed the optimal interfacial adhesion.

Effects of various long-term thermal aging levels on the morphology, rheology and self-healing performances of high-viscosity asphalt

Large macroporous structures of permeable asphalt pavement made high-viscosity asphalt (HVA) more susceptible to aging and failure. However, the standard pressure aging vessel (PAV) test was difficult to accurately emulate the long-term aging behavior of HVA. Hence, 1–5PAV aging levels of two HVAs (i.e. HVA-1 and HVA-2) were emulated by the simple aging test (SAT). Rheological analysis indicated that asphalt oxidation consistently dominated regardless of the long-term aging levels of HVAs. Combined with the fluorescence microscopy observation, HVA-2 with meticulous and uniform granular distribution was more resistant to aging than HVA-1 with coarse and continuously strip-like structures. Stress-strain curve analysis in linear amplitude sweep (LAS) test revealed that the accumulated strain energy (ASE) representing the overall mechanical properties of HVAs first increased and then decreased as the long-term aging level grew. The continuous repeated LAS (RLAS) test further reflected that the yield stress, yield strain and ASE of HVAs gradually decreased as the LAS loading number increased at initial long-term aging states; but as the sustained growth of aging level, the stress-strain curve of HVAs become increasingly chaotic until remarkable strain hardening occurred. Furthermore, RLAS-based self-healing (RLASSH) test was developed by introducing intermittent time into RLAS test. The variation of ratio of ASE decrease can characterize the self-healing performance of HVAs. RLASSH test showed that the self-healing performance of HVAs was unstable at 1–3PAV aging level, and the HVAs with 4 or 5PAV aging levels completely lost their self-healing performance. Overall, with the increase in long-term aging levels, significant differences were observed in the evolution characteristics of morphology, rheology and self-healing performances of different HVAs. This study helps to understand the rheology and self-healing performance evolution pattern of HVA during long-term service.

Research on Low-Cost High-Viscosity Asphalt and Its Performance for Porous Asphalt Pavement.

To develop a cost-effective, high-viscosity asphalt for porous asphalt pavement, we utilized SBS, tackifier, and solubilizer as the main raw materials, identified the optimal composition through an orthogonal experiment of three factors and three levels, and prepared a low-cost high-viscosity asphalt. We compared its conventional and rheological properties against those of rubber asphalt, SBS modified asphalt, and matrix asphalt, employing fluorescence microscopy and Fourier transform infrared spectroscopy for microstructural analysis. The results indicate that the optimal formula composition for high-viscosity asphalt was 4-5% styrene-butadiene-styrene (SBS) + 1-2% tackifier +0-3% solubilizer +0.15% stabilizer. The components evenly dispersed and the performances were enhanced with chemical and physical modification. Compared with SBS modified asphalt, rubber asphalt, and matrix asphalt, the softening point, 5 °C ductility, and 60 °C dynamic viscosity of high-viscosity asphalt were significantly improved, while the 175 °C Brookfield viscosity was equivalent to SBS modified asphalt. In particular, the 60 °C dynamic viscosity reaches 383,180 Pa·s. Rheological tests indicate that the high- and low-temperature grade of high-viscosity asphalt reaches 88-18 °C, and that high-viscosity asphalt has the best high-temperature resistance to permanent deformation and low-temperature resistance to cracking. It can save about 30% cost compared to commercially available high-viscosity asphalt, which is conducive to the promotion and application of porous asphalt pavement.

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.

Rheological properties of warm mixed high viscosity asphalt at high and low temperatures.

The rheological properties of asphalt can well reflect its road performance, but the rheological properties of warm mix high viscosity asphalt (HVA) are unclear. In order to study the effect of warm mixing agent on rheological properties of HVA, two kinds of warm mixing agent EC120 (EC) and Evotherm M1 (M1) were selected to prepare warm mix HVA. The rheological properties of warm mix HVA at high temperature (135~195°C), medium temperature (0~80°C) and low temperature (-6~18°C) were studied by Brinell rotary viscosity test, dynamic shear rheological test (including temperature scanning, frequency scanning, linear amplitude scanning) and bending beam rheological test. The test results show that both EC and M1 have good viscosity reduction effect on HVA at high temperature, and can effectively reduce the construction temperature. At medium temperature, M1 can effectively improve the fatigue resistance of HVA, and the fatigue life can be increased by about 30% when the dosage is 0.6%. EC can increase the rutting factor of HVA and improve its resistance to deformation, but it will reduce its fatigue performance. When the dosage is 4%, the fatigue life will be reduced by about 9%. At low temperature, M1 can reduce the creep stiffness S, increase the creep rate m, and improve the low temperature performance of HVA, while EC has the opposite effect, weakening the low temperature performance of HVA. The results are helpful to understand the rheological properties of warm mix HVA and promote its application.

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.

Analysis of asphalt microscopic and force curves under water-temperature coupling with AFM

Asphalt, as a crucial material in road construction, is affected by external environmental factors, among which water and temperature are the primary causes of water damage to asphalt pavements. Different hydro-thermal environments can cause varying types of damage to asphalt or the asphalt-aggregate interface. To analyze the micro-performance changes of different types of asphalt under various hydro-thermal environments, this study conducts tests onPG64–22 matrix asphalt, PG76–22 SBS-modified asphalt and PG82–34 high viscosity asphalt under different hydro-thermal coupling and freeze-thaw cycle conditions using Atomic Force Microscopy (AFM). The analysis is based on the obtained micro-morphology images and mechanical properties, exploring the impact mechanisms of different hydro-thermal environments on various asphalts. Results show that under different hydro-thermal conditions, the three asphalts exhibit different morphological changes: the asphalt surface's “bee-shaped structure” is gradually destroyed after hydro-thermal coupling, while a “disappearance-reappearance” phenomenon is observed under freeze-thaw cycles. Moreover, the roughness of the two modified asphalts shows a different trend from that of the matrix asphalt, indicating that the modifier alters the micro-structure of asphalt to some extent. Under hydro-thermal coupling, the adhesion force of the three asphalts decreases linearly, with matrix asphalt decreasing by 89.2% after 3 hours, SBS modified asphalt by 63.1%, and high-viscosity asphalt by 23.9%, showing that high-viscosity asphalt has better waterproof and heat-resistant performance. During freeze-thaw cycles, the adhesion force between the asphalt and the tip shows varying degrees of recovery. Additionally, there are differences in adhesion force across different areas of the asphalt surface, which tend to diminish with hydro-thermal coupling or freeze-thaw cycles. These results indicate that hydro-thermal coupling and freeze-thaw cycles have different mechanisms of damage to the internal structure of asphalt, providing important data for understanding the damage mechanisms in depth.

Evaluation of cooling effect and road performance of warm mixed high viscosity porous asphalt mixture.

In order to study the effect of different warm mixing agents on the cooling and road performance of porous mixture bonded with High Viscosity Asphalt (HVA), the Superpave Gyratory Compactor (SGC) was proposed to conduct variable temperature compaction test on the warm mixed porous asphalt mixture. The relationship between the compaction difficulty coefficient and the temperature of the mixture was obtained by regression, and the mixing and compacting temperature and cooling effect of the warm mixed porous asphalt mixture were determined. Then, the influence of Evotherm M1 and EC120 warm mix agents on the performance of porous asphalt mixture was compared by rutting tests, beam bending tests, immersion Marshall tests, freeze-thaw splitting tests, and penetration strength tests. The results show that two types of warm mixing agents can reduce the mixing and rolling temperatures of the mixture by more than 10°C. The addition of warm mix agents will increase the high temperature stability, water stability, and shear resistance of porous asphalt mixtures. For the improvement effect of high temperature stability, EC120 warm mixing agent is greater than Evotherm M1 warm mixing agent, and for the improvement effect of water stability, Evotherm M1 warm mixing agent is greater than EC120 warm mixing agent. For shear resistance, the improvement effect of both is equivalent, with a penetration strength increase of about 3% to 4%. For low temperature performance, Evotherm M1 warm mixing agent improved the low temperature performance, while EC120 warm mixing agent showed the opposite effect.

Effects of thermal aging level on the morphological structures, rheological properties and fatigue characteristics of high-viscosity asphalts

High-viscosity asphalt (HVA) provides excellent cracking and rutting resistance for ecological permeable pavement. However, HVA suffers from severe aging due to higher construction temperatures and rich porous structures, which limited its applications for urban sustainability. Currently there is still a lack of knowledge about the thermal aging effects and mechanisms of HVA. In this study, the effects of thermal aging on the morphological structures, rheological and fatigue properties of two HVAs (i.e. HVA-1 and HVA-2) at five aging levels via Simple Aging Test (SAT) are systematically investigated. HVA-1, characterized by loosen and coarse reticulated structures, undergoes significant structural changes during aging, whereas HVA-2, characterized by dense and fine reticulated structures, experiences fewer alterations. The changes in the modulus master curves of HVAs become more gradual after aging, indicating the reduced temperature sensitivity. Multiple stress creep recovery results reflect that two types of HVAs exhibit totally different dominance of oxidation or polymer degradation depending on aging level. Liner amplitude sweep (LAS) results based on damage mechanics analysis reveal that aging leads to an increase in the accumulated strain energy observed in stress-strain curves for both HVAs. As aging progresses, the proportion of elastic energy decreases due to polymer degradation, resulting in a reduction in fatigue life. Especially, the fatigue life of aged HVAs significantly decreases after SAT40. LAS results based on fracture mechanics analysis show that the crack length increases with aging due to polymer degradation and asphalt phase hardening. Aging effect on crack length was limited at initial stage but becomes more significant as crack extends. As aging deepens, the crack initial stage of HVAs tends to lengthen while the crack extension stage tends to shorten. Moreover, the crack growth process of HVAs follows a two-stage behavior of crack initiation and propagation under certain aging levels from the relationship between energy release rate and crack propagation rate. Overall, the thermal aging kinetics of various HVAs differ significantly in the structures, rheological and fatigue properties as aging deepens. HVA-2 with loosen and coarse structures exhibits greater aging resistance and lower temperature sensitivity than HVA-1 with dense and fine structures.

Study on the Performance of Phase-Change Self-Regulating Permeable Asphalt Pavement

Under low-temperature conditions in winter, asphalt pavement is prone to cracking, icing and other distresses, which affect its safety and comfort. Therefore, by incorporating phase-change materials into asphalt and conducting relevant performance studies, the aim is to alleviate low-temperature distress and regulate road surface temperature and expand the application of phase-change materials in asphalt pavement. We mixed the selected phase-change materials with different dosages into the matrix asphalt to prepare phase-change temperature-regulating asphalt and tested the four basic indicators: road performance, latent heat characteristics, temperature-regulating performance, and rheological properties of phase-change asphalt and its mixture. The research results indicate that with the increase in phase-change material content, the penetration, softening point, ductility, and dynamic viscosity of phase-change high-viscosity asphalt gradually increase. Under the constant temperature test conditions of −2.5 °C and −5 °C, the surface icing speed of asphalt binder specimens mixed with phase-change materials is slower than that of specimens without phase-change materials. Adding phase-change materials can improve the high-temperature and low-temperature PG grading of high-viscosity asphalt, effectively improving its high-temperature rutting resistance and low-temperature cracking performance. According to the temperature regulation test results, phase-change temperature-regulating asphalt has a certain regulating effect on temperature under low-temperature conditions, which can slow down the cooling rate of asphalt, reduce the thermal conductivity of permeable asphalt mixture by more than 50%, increase the temperature regulation rate by more than 30%, and improve the ice-melting and snow-melting ability by more than 20%. Phase-change materials have almost no effect on the porosity of permeable asphalt mixtures and can effectively improve the water stability, low-temperature crack resistance, and antiflying performance of permeable asphalt mixtures. Their Marshall stability and rutting stability decrease, but still meet the requirements of the specifications. Applying phase-change materials to permeable asphalt pavement can automatically adjust the temperature of the pavement, reduce the cooling rate of the asphalt pavement during cooling, alleviate the problem of snow and ice accumulation on the asphalt pavement in winter, and thereby improve the performance of permeable asphalt pavement against freeze–thaw cycles.

Interface interaction between high viscosity asphalt and aggregate: A multi-scale study based on experiments and molecular dynamics simulation

The pull-off strength, boiling peeling ratio, adhesion work, stripping work, interaction energy, nanoindentation resistance force, and hydrogen bond distribution were analyzed based on laboratory tests and molecular dynamics simulation. The interface interaction between the original, aged, or regenerated high-viscosity asphalt (HVA) and the acid or alkali aggregate component in the aqueous or anhydrous environment was clarified from multi-scales of macro, micro, and nano scales. The results show that the pulling strength has an obvious positive correlation with the interfacial adhesion work, which can evaluate the interfacial adhesion state with water. The boiling peeling ratio has an obvious positive correlation with the interface stripping work, which can evaluate the interfacial adhesion state without water. The ratio of adhesion work to stripping work can characterize the interface water-stripping resistance. In nanoindentation simulation, the vertical resistance force of the indenter characterizes the interaction between HVA and the aggregate indenter. The interfacial adhesion state deteriorates with the deepening of HVA aging. Further addition of a high viscosity modifier (HVM) in the regenerated HVA effectively restores the interfacial adhesion state. The higher temperature causes worse interfacial adhesion, and the hydrogen bond ratio, adhesion, and water-stripping resistance of the interface between the HVA and alkaline aggregate components are much better than those between the HVA and acid aggregate components. Van der Waals force plays a leading role in interfacial adhesion. With the deepening of aging, the oxygen-containing functional groups such as carbonyl and sulfoxide in HVA increase, in which it is easy for oxygen atoms to form hydrogen bonds with water, so the water-stripping resistance of the interface decreases.

Thermal Aging Degradation of High-Viscosity Asphalt Based on Rheological Methods.

With the acceleration of the construction of sponge cities in China, porous asphalt pavement (PA) is has been widely used. High-viscosity asphalt (HVA) is the core material in building PA because it has good rheology properties, which can provide good raveling and rutting resistance. However, due to the open-graded structure of PA, HVA was more susceptible to rapid aging, which significantly affects the durability of PA. To investigate the thermal aging effect on the rheological properties of self-modified HVA (SHVA), five types of asphalts were aged using a rolling thin film oven (RTFO) and pressure aging vessel (PAV). Then, rheological tests were adopted, such as temperature sweep test (TS), repeated creep and recovery test (RCR), and bending beam rheometer test (BBR). The results indicate that during the aging process, the oxidation-induced hardening effect of neat asphalt and the degradation-induced softening effect of the modifier changes the rheology properties of HVA significantly. As the aging progresses, the contribution of the modifiers of HVA to anti-aging performance is greatly reduced. At high temperatures, HVA demonstrates better anti-aging performance than conventional styrene-butadiene-styrene (SBS)-modified asphalt (Guo Chuang, GC). The change of the high-temperature rheological indices of the two HVA types (SHVA and TAFPACK-super HVA (TPS)) showed a smaller activation energy index (EAI), a more considerable viscous component of binder creep stiffness (Gv), and more minor accumulated stain (racc), indicating a more significant anti-short-term and long-term aging performance, which is beneficial to the high-temperature performance of asphalts. However, the changes in low-temperature rheological properties do not align with those in high-temperature rheological properties after long-term aging. The BBR test results reveal that TPS exhibits worse low-temperature performance than GC and SHVA. During the thermal aging process, the contribution rate of the modifiers in SHVA against RTFO and PAV aging is higher than that of the modifiers in TPS, which contributes to the superior anti-aging property. Overall, SHVA demonstrates the best anti-aging performance among the five asphalts tested.

Adhesion Properties of Recycled High-Viscosity Asphalt-Aggregate Interface under Dynamic Water Erosion.

The drainage of asphalt pavement requires the use of a large amount of high-viscosity-modified asphalt, which faces the service environment under dynamic water erosion. The feasibility of recycling high-viscosity-modified asphalt should be investigated to facilitate sustainable infrastructure construction. This study used ultrasonic equipment to simulate dynamic water erosion test conditions and tested the adhesion performance of different types of recycled high-viscosity asphalt at various environmental temperatures. The adhesion energy index and microstructure of recycled high-viscosity asphalt were analyzed using the contact angle test and AFM test. The results demonstrate that the higher the environmental temperature, the worse the anti-stripping performance of recycled high-viscosity asphalt. From the perspective of adhesion performance indicators, a 6% recycling agent dosage is more conducive to restoring the performance of aged high-viscosity -modified asphalt. The AFM test showed that the microstructure of high-viscosity -modified asphalt represented significant changes with an increase in the recycling agent content, and the change in the adhesion force of recycled high-viscosity -modified asphalt was consistent with the results of macroscopic adhesion performance tests. This study illustrates the applicability of implementing regeneration technology for the recycling of aged drainage asphalt pavement.

Preparation and Properties of High-Viscosity Asphalt Using WTR, Terpene Resin, and APAO

Abstract In this research, a novel high-viscosity asphalt (HVA) is developed using renewable modifiers to reduce its environmental impact and cost over traditional polymer modifiers such as styrene-butadiene-styrene and Tafpack super. Waste tire rubber (WTR) was utilized to increase the viscosity and improve the rheological properties of asphalt matrix at a relatively low cost. Amorphous poly alpha olefin (APAO) and terpene resin (TR) were used in the study to promote the effect of WTR and reduce the reaction temperature of the modification process. The rheological properties of asphalt matrix, WTR rubber-modified asphalt (RMA), and HVA were evaluated by dynamic shear rheometer, and the internal microstructure was observed by fluorescence microscopy and Fourier transform infrared spectroscopy to evaluate the compatibility of the prepared asphalts. The reaction temperature was reduced by 20°C–30°C. The optimum dosage of WTR, APAO, and TR was determined as 20 percent asphalt by weight (wt%), 5 wt%, and 3 wt%, respectively. Experimental outcomes indicated that the optimum modifiers appreciably increased the viscosity by 2.5 times (higher than 20,000 Pa·s at 60°C) and increased the ductility and softening point of RMA by approximately 50 % and 10 %, respectively. The HVA exhibited greater resistance to permanent deformation at high temperatures and to cracks at low temperatures. Because of the chemical and physical reaction between the asphalt phase and WTR, the addition of APAO and TR promoted the swelling of rubber powder and improved the uniformity of the system.

Sustainable Utilization of Recycled Waste in High-Viscosity Asphalt Binders: Case for Improvement in Aging Resistance

Sustainable Utilization of Recycled Waste in High-Viscosity Asphalt Binders: Case for Improvement in Aging Resistance

Multiscale study on aging process and mechanism of high viscosity Asphalt: Macro-micro experiments and quantum chemical molecular simulation

Clarifying the aging mechanism of high viscosity asphalt (HVA) is the prerequisite for ensuring its durability, but there are relatively few studies on the aging mechanism of HVA under coupling effects. The quantum chemical simulation method can be applied to better reveal the mechanism of aging behavior from the molecule perspective compared with macro and micro tests. However, the quantum chemical method has not been applied in the HVA aging study. In this paper, the macro and micro tests were carried out to study the changes of macro properties, functional groups, molecular weight and microstructure of HVA after thermal oxygen aging. Quantum chemical simulation was conducted to analyze the reaction sites, steps and products of styrene–butadienestyrene (SBS) and asphalt components in HVA under the coupling effect of oxygen, water and ultraviolet. The results show that with the aging deepening, the penetration and ductility of HVA decrease, the softening point and complex modulus increase, the high-temperature performance increases and the low-temperature performance decreases. After short-term aging, the cross-linked structure destruction and the SBS degradation dominate, so the HVA viscosity decreases and the phase angle increases. After long-term aging, the polymerization of aromatics and saturates dominates, so the HVA viscosity increases and the phase angle increases. The most easily oxidized site in HVA is the carbon atom at the carbon–carbon bond in SBS molecule, followed by the carbon atom connected with the benzene ring in asphalt. SBS is easier to react with oxygen or water than asphalt, so SBS delays the aging of asphalt in HVA. Under different water content, the aging processes and products of SBS/asphalt components with oxygen/water are different, but the ultraviolet excitation does not change the reaction path. The HVA aging was enhanced with the water content increase or ultraviolet excitation by reducing the energy barrier in reaction.

Preparation and performance analysis of high-viscosity asphalt containing high-content SBS and crumb rubber by oxygen-free high-temperature treatment

Styrene-butadiene-styrene (SBS) and crumbed rubber (CR) are widely used for asphalt binder modification in the field of road materials. Especially, the high-viscosity asphalt with high-content SBS/CR modifiers has been applied for constructing the porous pavement and ultra-thin overlay. However, the workability of the SBS/CR modified asphalt still needs to be improved due to many unswollen polymer particles in the blended system. This work aims to propose an oxygen-free high-temperature treatment method to reduce the viscosity of SBS/CR-modified asphalt at construction temperature for better workability. Viscosities at 60 °C and 180 °C were tested to obtain the content of SBS, CR, and tackifying resin for high-viscosity asphalt; multiple physical tests were conducted to obtain acceptable heating temperature, initial pressure, and reacting time; the two high-viscosity asphalt binders cured under various conditions were compared through physics, chemistry, and rheology properties. The results show that the 70# asphalt incorporating 10% SBS, 6% CR, and 9% (by weight of asphalt binder) resin can prepare ideal high-viscosity asphalt binders. After high-speed shearing, it was recommended that CR-SBS-asphalt blends be cured in the reactor at the initial pressure of 3 MPa and temperature of 200 °C for 45 mins. The improved reaction conditions increased light components in a homogeneous and formed a stable modified asphalt blended system. Hence, the low-temperature performance and workability were improved, despite weakening the rutting resistance, which was still excellent at the high temperature.

Study of fatigue performance of fiber reinforced high-viscosity asphalt mastic based on rheology

Open-graded asphalt mixture pavement, with its functional benefits of drainage and noise reduction, holds promising engineering application potential. The high-viscosity asphalt mastic significantly influences the performance of this open-graded asphalt mixture. In this study, the fatigue performance of fiber reinforced high-viscosity asphalt mastic was investigated based on rheology. Shear rheometer was used to perform temperature sweep tests, time sweep tests, and linear amplitude sweep tests on the fiber reinforced high-viscosity asphalt mastic. The influences of filler/binder ratio, filler properties, fiber type, and content on the fatigue performance of the mastic were analyzed. Time sweep test data was used to establish a prediction equation for temperature-stress fatigue life of the mastic. The interconnectivity and differences between various fatigue life indicators were studied based on phenomenology and energy dissipation theory. The fatigue characteristics and damage mechanism of the mastic were investigated using a viscoelastic damage model, and the fatigue lives at different strain levels were observed. The research results indicate that fatigue damage of high-viscosity asphalt mastic mainly occurs at low temperatures. An increase in filler/binder ratio at the same temperature reduces the anti-fatigue performance of the mastic. Compared with dust, mineral powder has a larger specific surface area and better fatigue resistance performance. The established temperature-stress equation can accurately predict the fatigue life of mastic under different temperatures and stresses. The fatigue indicators Np20 and Nfm, based on energy dissipation theory, show a favorable linear relation with the fatigue indicator Nf50 based on phenomenology, and these three indicators are consistent in evaluating the fatigue performance and life of the mastic. Np20 and Nfm are found to be more applicable for evaluating the fatigue performance of fiber reinforced high-viscosity asphalt mastic. The fatigue life of the mastic decreases with increasing strain levels, and high-viscosity asphalt mastic containing basalt fiber shows better adaptability to complex traffic conditions.

Research on high-temperature rheological performance of fiber reinforced high-viscosity asphalt mastics

High-temperature performance of high-viscosity asphalt mastic containing fiber additive were studied by means of rheological analysis. The effects of two types of asphalt, two types of fillers, and two types of fibers with three fiber contents on the high-temperature rheological properties of asphalt mastic were evaluated by temperature sweep test, multiple stress creep recovery test, and frequency sweep test using a dynamic shear rheometer. The master curve of fiber reinforced high-viscosity asphalt mastic and phase angle were constructed using 2S2P1D model. The results show that the nature of asphalt plays a leading role in improving the resistance to deformation of asphalt mastic at high temperature, compared with the type of mineral powder. For the short-term aging asphalt mastic, with temperature increasing, the unrecoverable creep compliance gradually increases and the differences between asphalt mastic with different fiber contents also become greater. The creep recovery rate of mastic with basalt fiber is much higher than that of polyester fiber under the same conditions. For long-term aging asphalt mastic, compared with increasing fiber content, the fiber type has more significant influence on the storage modulus. 2S2P1D model can well fit the master curve of the complex modulus of fiber reinforced high-viscosity asphalt mastic, but poorly fit with the phase angle. From master curves, it finds that the enhancement of the fiber to mastic is prominent in the low frequency which is corresponding to the extreme high-temperature condition.