Low-temperature Cracking Resistance Research Articles

Study on the Characteristics of Steel Slag and its Road Performance in Asphalt Mixture

Based on the characteristics of steel slag, the application progress of steel slag as aggregate in asphalt mixture is summarized. Firstly, the differences in mechanical properties, chemical composition and physical structure of steel slag aggregates treated by different methods are summarized. The surface structure of steel slag is rough and rich in edges and corners, showing good wear resistance and crushing resistance, but there are also problems such as high density, high water absorption and volume instability. Among them, volume instability is the key factor affecting the application of steel slag in asphalt mixture. Then, the effects of steel slag aggregate on the road performance of asphalt mixture, such as water stability, rutting resistance, high temperature stability and low temperature cracking resistance, are summarized in detail. It is found that steel slag instead of coarse aggregate in asphalt mixture can improve the performance of skid resistance, rutting resistance and fatigue resistance. The water damage performance is due to the different sources of steel slag, and the uncertainty of the change results is large. On the whole, steel slag instead of aggregate can improve the road performance to a certain extent, but the volume of steel slag aggregate is unstable, which may bring some variability. In the process of road application, targeted regulation should be carried out to ensure the stability of asphalt mixture performance.

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.

Study on the Effect of Hot and Humid Environmental Factors on the Mechanical Properties of Asphalt Concrete.

To investigate the effect of hot and humid environmental factors on the mechanical properties of asphalt mixtures research, in this paper, the dynamic modulus of asphalt mixtures under the effects of aging, dry-wet cycling, and coupled effects of aging and dry-wet cycling were measured by the simple performance tester (SPT) system, and the dynamic modulus principal curves were fitted based on the sigmoidal function. The results show that under the aging effect, the dynamic modulus of asphalt mixture increases with the aging degree; the dynamic modulus of short-term aged, medium-term aged, long-term aged, and ultra-long-term aged asphalt mixtures increased by 9.3%, 26.4%, 44.8%, and 57%, respectively, compared to unaged asphalt mixtures at 20 °C and 10 Hz; the high-temperature stability performance is enhanced, and the low temperature cracking resistance performance is enhanced; under the dry-wet cycle, the aging effect of asphalt water is more obvious in the early stage, and dynamic modulus of resilience of the mixture is slightly increased. In the long-term wet-dry cycle process, water on the asphalt and aggregate erosion increased, the structural bearing capacity attenuation, and the dynamic modulus of rebound greatly reduced at 20 °C and 10 Hz. For example, the dynamic modulus of asphalt mixtures with seven wet and dry cycles increased by 3% compared to asphalt mixtures without wet and dry cycles, and the dynamic modulus of asphalt mixtures with 14 cycles of wet and dry cycles and 21 cycles of wet and dry cycles decreased by 10.8% and 16.5%, respectively, compared to asphalt mixtures without wet and dry cycles. The main curve as a whole shifted downward; the high-temperature performance decreased significantly; in the aging wet-dry cycle coupling, the aging asphalt mixture is more susceptible to water erosion, and the first wet-dry cycle after the mix by the degree of water erosion is relatively small, along with the dynamic modulus of rebound. The dynamic modulus of resilience is relatively larger, and the high-temperature performance is relatively better, while the low-temperature performance is worse.

Waste coffee biochar and bi-oil composite modified rejuvenated asphalt: Preparation, characterization, and performance evaluation

In the realm of sustainable road construction, bio-oil has emerged as a promising and eco-friendly alternative for rejuvenating aged asphalt. Nevertheless, challenges arise due to poor stability, diminished performance at elevated temperatures, and limited anti-aging properties. This study introduces an innovative approach by blending biochar, obtained from the pyrolysis of waste coffee grounds, into bio-oil to create a composite modified regenerator. Initially, the study conducts a microscopic characterization of the biochar using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). Subsequently, the rheological properties of this composite rejuvenated asphalt are evaluated across low, moderate, and high-temperature ranges using bending beam rheometer (BBR), linear amplitude sweep (LAS), and multiple stress creep and recovery (MSCR) tests. Departing from the traditional emphasis on initial property restoration, it further delves into performance alterations after re-aging of rejuvenated asphalt through temperature sweep (TS) and Fourier transform infrared spectroscopy (FTIR) tests, providing a comprehensive assessment of the anti-aging characteristics of rejuvenated asphalt. Additionally, gel permeation chromatography (GPC) is employed to quantitatively analyze the changes in asphalt molecular weight distribution. The microscopic characterization reveals the development of a rough and porous structure within the biochar, facilitating enhanced adhesion and interaction between the rejuvenator and the asphalt binder. Moreover, bio-oil rejuvenated asphalt exhibits excellent low-temperature crack resistance and moderate-temperature fatigue resistance. Following the incorporation of biochar, notable enhancements in high-temperature rutting resistance and anti-aging properties are observed, validating the efficacy of the biochar with bio-oil composite modified regenerator. To achieve optimal performance outcomes, a biochar content of 6 % (as a proportion of aged asphalt), corresponding to a 1:1 ratio of biochar to bio-oil, is recommended. Under this condition, the properties of the composite modified rejuvenated asphalt demonstrate comparability to those of the original asphalt. In summary, this research underscores the potential for integrating waste coffee biochar material into infrastructure development, thereby promoting circular economy principles and advancing more sustainable construction practices.

Study on preparation and properties of GA/h-BN modified road petroleum asphalt based on ball milling method

ABSTRACT Graphene (GA), a two-dimensional nanomaterial, is noted for its exceptional mechanical, thermal and electrical properties. The integration of GA with road materials can potentially develop high-performance composite road materials. However, its application in road engineering is limited by complex preparation processes and high costs. This paper presents a GA/h-BN composite material developed through mechanical stripping using flake graphite and hexagonal boron nitride (h-BN). A mathematical model was created employing uniform design methods and optimised through numerical analysis to identify the optimal process parameters. Microscopic techniques, including X-ray diffraction and atomic force microscopy, confirmed that the GA/h-BN product consists of approximately three layers, forming a ‘graphene-hexagonal boron nitride-graphene’ nanolayer structure. The composite was then used to modify matrix asphalt, with performance tests determining the optimal dosage. The results indicated that adding 0.3% GA/h-BN significantly improved the asphalt's high- and low-temperature performance, fatigue resistance and cracking resistance. Moreover, the evaluation of the physical properties of matrix asphalt modified solely with h-BN revealed that, despite h-BN comprising 70% of the mass fraction in the GA/h-BN modifier, it exerted a minimal impact on the performance of the asphalt. This study introduces a novel source of raw materials for the application of GA in road engineering.

Experimental Study on Pavement Performance of Warm High Modulus Mixture WHMM-13

In order to solve the dusting and rutting problems of hot mix asphalt mixture during construction and operation, rutting test, bending test, Marshall stability test, freeze-thaw splitting test, uniaxial compression dynamic modulus test, overlay test, and four-point bending fatigue life test are applied on WHMM-13 to study the high-temperature stability, low-temperature cracking resistance, water stability, anti-reflection crack performance and fatigue durability in comparison with HMM-13. The results show that, compared to HMM-13, the dynamic stability and dynamic modulus (45 ℃, 10 Hz) of WHMM- 13 are improved by 10.0% and 47% respectively, and the rutting depth is reduced by 27.3%, indicating that the high temperature stability of WHMM-13 has been greatly improved. As for low temperature cracking resistance, the bending failure strain, stiffness modulus, flexural tensile strength and rupture energy of WHMM-13 are slightly lower than those of HMM-13. As for water stability, the residual stability of WHMM-13 in immersion Marshall test is 87.5%, and the splitting strength is 82.3%, both higher than that of HMM-13. As for anti-reflection crack performance, the total tensile rupture energy of WHMM-13 is 2.32 times that of HMM-13, with cracking resistance index (CRI) increased by 25%, which shows that WHMM-13 has better strength, can effectively prevent the crack from spreading and effectively improve the cracking resistance capacity of asphalt pavement. As for fatigue durability, the fatigue life of WHMM-13 is 5.4% lower than that of HMM-13, with bending stiffness modulus and cumulative dissipation energy reduced by 11.3% and 2.8% respectively, indicating that the fatigue durability of WHMM-13 is slightly reduced.

Performance of Asphalt Mixtures Modified with Desulfurized Rubber and Rock Asphalt Composites

This study explores the performance of asphalt mixtures modified with North American rock asphalt and desulfurized rubber particles at varying rubber-to-asphalt ratios ranging from 18% to 36% by weight. A comprehensive set of laboratory tests, including high-temperature rutting tests, low-temperature bending tests, indirect tensile tests, and freeze–thaw splitting tests, were conducted to evaluate the modified mixtures. The results indicate that both wet and dry blending methods produce mixtures that meet technical requirements, with the optimal asphalt-to-aggregate ratio determined to be 7.1%. At a rubber-to-asphalt ratio of 18%, the wet blending method slightly improves high-temperature rutting resistance compared to the dry method. However, an increase in rubber content generally enhances rutting resistance regardless of the blending technique. The wet blending method excels in low-temperature crack resistance, possibly due to better rubber dispersion, while an increase in rubber content diminishes crack resistance due to a thinning asphalt film. In terms of fatigue performance, the dry blending method results in significantly longer fatigue life, with a 27% rubber-to-asphalt ratio exhibiting optimal balance. The dry method consistently outperforms the wet method in water stability, and the resistance to water damage increases with rubber content. In conclusion, this study provides valuable insights into optimizing rubber-to-asphalt ratios and blending methods for various application needs, showcasing the benefits of rock asphalt and desulfurized rubber particles in asphalt modification.

Effects of antioxidants on chemical and rheological properties of asphalt binders from different crude oil sources

Antioxidants can effectively mitigate or delay the oxidative aging degradation of asphalt binder, thereby improving pavement durability. While research has largely concentrated on the application of antioxidants to asphalt binders from a single source, limited studies have explored their effects on binders derived from different crude oil sources. Moreover, the relationship between the chemical and rheological properties of antioxidant-modified asphalt binders remains insufficiently understood. In this study, three antioxidants - zinc diethyldithiocarbamate (ZDC), Irganox 1010 and kraft lignin - were utilized and blended with base binders sourced from three distinct regions globally. Fourier transform infrared spectroscopy (FTIR) was utilized to analyze the impact of these antioxidants on the chemical composition of aged binders. Additionally, dynamic shear rheometer (DSR) and bending beam rheometer (BBR) tests were conducted to assess the high- and low-temperature performance of the antioxidant-modified binders, identifying the most effective antioxidant. The linear amplitude sweep (LAS) test further evaluated the performance of ZDC across binders from different crude oil sources. The results revealed three key findings: first, chemical functional group changes due to antioxidants are not always reflected in rheological performance; second, ZDC demonstrated superior performance across different base binders, as evidenced by improved aging indices, high-temperature rutting resistance, and enhanced fatigue and low-temperature cracking resistance; and third, asphalt binders from different crude oil sources exhibit varying sensitivities to antioxidant type and dosage. This study underscores the necessity of determining optimal antioxidant dosages for different asphalt binders, as the relationship between antioxidant dosage and effectiveness is not straightforward.

Rheological and Aging Properties of Nano-Clay/SBS Composite-Modified Asphalt.

Nano-organic montmorillonite (OMMT) not only inhibits the harmful asphalt fume generation during the production and construction processes of asphalt mixtures but also effectively improves the performance of asphalt pavements. In order to prepare asphalt materials with smoke suppression effects and good road performance, this study selects nano-OMMT and SBS-modified asphalt for composite modification of asphalt mixtures and systematically investigates its road performance. Through the temperature sweep test, the frequency sweep test, the multiple stress creep recovery (MSCR) test, the bending beam rheometer (BBR) test, and the atomic force microscope (AFM) test, the high-temperature rheological properties, low-temperature rheological properties, high-temperature properties and aging resistance of the modified asphalt are studied. The research findings indicate that OMMT can effectively reduce the sensitivity of modified asphalt to load stress and improve its high-temperature rheological properties. SBS-modified asphalt shows increased creep stiffness and a decreased creep rate after OMMT modification, resulting in reduced flexibility and decreased low-temperature crack resistance. After short-term and long-term aging, the complex modulus aging index of OMMT/SBS composite-modified asphalt is lower than that of SBS-modified asphalt, and the phase angle aging index is higher than that of SBS-modified asphalt, demonstrating that OMMT enhances the aging resistance of SBS-modified asphalt. OMMT inhibits oxidation reactions in the asphalt matrix, reducing the formation of C=O and S=O bonds, thereby slowing down the aging process of modified asphalt and improving its aging resistance.

Mechanochemical Upcycling of Waste Polypropylene into Warm-Mix Modifier for Asphalt Pavement Incorporating Recycled Concrete Aggregates.

To solve the problems on resource utilization and environmental pollution of waste concrete and waste polypropylene (PP) plastics, the recycling of them into asphalt pavement is a feasible approach. Considering the high melting temperature of waste PP, this study adopted a thermal-and-mechanochemical method to convert waste PP into high-performance warm-mix asphalt modifiers (PPMs) through the hybrid use of dicumyl peroxide (DCP), maleic anhydride (MAH), and epoxidized soybean oil (ESO) for preparing an asphalt mixture (RCAAM) containing recycled concrete aggregate (RCA). For the prepared RCAAM containing PPMs, the mixing temperature was about 30 °C lower than that of the hot-mix RCAAM containing untreated PP. Further, the high-temperature property, low-temperature crack resistance, moisture-induced damage resistance, and fatigue resistance of the RCAAM were characterized. The results indicated that the maximum flexural strain of the RCAAM increased by 7.8~21.4% after using PPMs, while the sectional fractures of the asphalt binder were reduced after damaging at low temperature. The use of ESO in PPMs can promote the cohesion enhancement of the asphalt binder and also improve the high-temperature deformation resistance and fatigue performance of the RCAAM. Notably, the warm-mix epoxidized PPMA mixture worked better close to the hot-mix untreated PPMA mixture, even after the mixing temperature was reduced by 30 °C.

Feasibility and environmental assessment of introducing waste polyurethane from wind turbine blades as a modifier for asphalt

Recycled glass fibers from wind turbine blades have significant potential for enhancing the performance of asphalt mixtures. However, the impact of residual polyurethane (PU) components on asphalt performance remains uncertain, presenting a challenge to the high-value utilization of wind turbine blades in pavement engineering. This study investigates the effects of waste polyurethane (WPU) on the rheological properties and compatibility of SBS modified asphalt, widely used in pavement engineering under various temperature conditions. Molecular dynamics (MD) simulations were employed to analyze the underlying mechanisms. The results reveal that incorporating WPU improves the rutting factor and creep recovery rate of SBS modified asphalt, demonstrating superior high-temperature performance compared to SBS modified asphalt alone. The synergistic effect of WPU and SBS significantly enhances low-temperature crack resistance and overall asphalt compatibility. Additionally, the interaction between SBS and the four components of asphalt is strengthened, and diffusion mobility is reduced due to WPU incorporation. This indicates that WPU promotes a more compact structure and a higher relative concentration of SBS and the four components within the spatial system, thereby enhancing the stability of the WPU/SBS modified asphalt system. Furthermore, using WPU in asphalt mixtures not only avoids environmental pollution compared to traditional disposal methods but also offers considerable long-term economic benefits. Overall, WPU positively impacts the rheological properties and compatibility of SBS-modified asphalt, suggesting that processed wind turbine blades can be a viable solution for enhancing asphalt mixture performance.

A study of fine-scale low-temperature cracking in geopolymer grouted porous asphalt mixtures based on real aggregate profile modeling

At a micro-scale level, grouted porous asphalt mixtures are multiphase composites consisting of aggregates, asphalt mortar, filler, asphalt mortar-aggregate interfacial transition zone, and asphalt mortar-filler interfacial transition zone. It exhibits different mechanical behavior under different temperatures and loading conditions. Compared with aggregate, asphalt mortar, and filler, the interfacial transition zone (ITZ) is more prone to damage at low temperatures, with both the fine structure and the nature of the contact interface having a significant effect on the overall strength and crack resistance of the material. To evaluate the influence of ITZ and filler material properties on the cracking resistance of the material, a grouted porous asphalt mixture model based on the real aggregate shape was established using finite element modeling. A cohesive zone model (CZM) was employed to characterize the internal mechanical behavior of the material, and a mesoscale damage simulation was performed for the grouted asphalt mixture. The study revealed the influence of different interfacial and filler material properties on the low temperature cracking resistance and proposed a design approach for anti-cracking grouted asphalt mixtures. The findings indicated that interfacial transition zone (ITZ) and filler properties play a crucial role on determining the damage characteristics. Increasing the ITZ and filler properties significantly enhanced the low temperature crack resistance of the grouted asphalt mixture.

Influence of crack configurations of asphalt mortar on the loading response characteristics of cracks under low-temperature conditions

Asphalt mortar is the base material used in asphalt concrete, and its mechanical properties directly affect those of the prepared asphalt concrete. An analysis of the loading response characteristics of cracks in asphalt mortar under low-temperature conditions can help reveal the interaction effect of multiple cracks in asphalt concrete and the influence mechanism of aggregates on the crack propagation and evolution behaviors. In this study, various forms of pre-cracks were generated in asphalt mortar specimens using the water jet cutting technology. Combined with the discrete element method (DEM), an indirect tensile (IDT) test and a virtual IDT test were conducted to analyze the effects of the crack deflection angle (β) and crack length (r) on the crack propagation behavior from macro- and meso-perspectives. The main results showed that: (1) Changes in the crack shape parameters (β and r) not only induced multiple branch cracks in the asphalt mortar but also led to the development of II Mode fractures; (2) With the increase in the crack shape parameters, the low-temperature crack resistance of the asphalt mortar decreased, with β having a greater effect on the crack propagation behavior than r; (3) At the mesoscale, with the increase in the crack shape parameters, there was a gradual transformation of the fracture mode from I Mode to II Mode, and the crack propagation process accelerated, resulting in a significant decrease in the low-temperature crack resistance at the macroscale. The research results establish a theoretical foundation for revealing the characteristics of multi-crack propagation in asphalt concrete under environmental influences, and offer technical support for pavement crack repair and maintenance.

Laboratory evaluation of synergistic blending with SBS-modified bitumen and rejuvenator to enhance the performance of recycled bitumen with a high content of RAP materials

Reclaimed asphalt pavement (RAP) stands as a pivotal construction material widely used in asphalt pavement rehabilitation. The prevailing focus and trajectory revolve around increasing the proportion and utility of RAP materials. However, the potential for temperature and fatigue cracking increases with the dosage of RAP materials. In this study, SBS modified bitumen (SBSMB) and four rejuvenators were combined synergistically with aged asphalt to enhance the performances of the recycled bitumen with high RAP content and consequently augment the value of the RAP material, all while ensuring compatibility between the SBSMB and aged base bitumen. Initially, the base bitumen was aged using a pressure aging vessel (PAV) test. Subsequently, a selection of virgin bitumen (VB), SBSMB, and four rejuvenators were utilized to revitalize the aged bitumen. A comprehensive battery of tests, encompassing conventional tests, temperature sweep, frequency sweep, multiple stress creep recovery (MSCR), bending beam rheometer (BBR), and linear amplitude sweep (LAS), were carried out to characterize the rheological properties. Finally, Fourier transform infrared spectroscopy (FTIR) was employed, along with the determination of polystyrene index (IPS) and polybutadiene index (IPB), to evaluate the compatibility between SBSMB and aged base bitumen. The results underscore that the incorporation of SBSMB and rejuvenator comprehensively enhances high-temperature performance and fatigue cracking resistance while effectively reinstating low-temperature cracking resistance. Furthermore, the values of IPS, IPB, and IPS/IPB exhibit an increase with the addition of a rejuvenator, indicating its potential to improve the compatibility between SBSMB and aged base bitumen. Thus, this research proposes a more cost-effective and environmentally sustainable approach to bolstering conventional asphalt pavement performance and grade.

Study on Low Temperature Cracking Resistance of Carbon Fiber Geogrid Reinforced Asphalt Pavement Surface Combined Body.

Currently, there are limitations in the research on the use of carbon fiber geogrids to prevent low-temperature cracking in asphalt pavements. This study aims to comparatively investigate the effects of carbon fiber-based geogrid type and dense-graded asphalt concrete mixture (AC) surface combined body (SCB) type on the low-temperature cracking resistance of reinforced asphalt pavement through low-temperature bending damage tests. Two geogrid types were prepared: a carbon fiber geogrid (CCF) and a glass/carbon fiber composite qualified geogrid (GCF). Two SCB types were studied: AC-13/AC-20 and AC-20/AC-25. The results show that the improvement in the flexural tensile strength of CCF is similar to that for GCF. Moreover, under reinforced conditions, the improvement in the low-temperature cracking resistance of AC-20/AC-25 is better than that for AC-13/AC-20 by 16.26-24.57%. Based on the analysis, the reasonable ratio range of the aperture sizes to the major particle sizes in the dense gradation can achieve a more effective interlocking effect. This can improve the low-temperature cracking resistance of carbon fiber-based geogrid-reinforced samples. Then, increasing the bending absorption energy is a key way of improving the low-temperature cracking resistance of carbon fiber-based geogrid reinforcements. Eventually, the fracture type of carbon fiber-based geogrid-reinforced samples is a mixed plastic-brittle fracture. These results can provide a reference for the road failure analysis of geogrid-reinforced asphalt pavement.

Performance assessment of composite modified bitumen integrated with desulfurized crumb rubber and SBS modifier as waterproofing adhesive layer

Performance of the waterproofing adhesive layer played a critical role for governing duration of bridge deck paving system due to harsh service conditions. To develop a new type of modified bitumen suitable for the layer between bridge deck and overlaid asphalt, this study investigated the performance of composite modified bitumen (CMB) integrated with desulfurized crumb rubber (DCR) and SBS modifier. The influence of DCR and SBS additive on rheological behavior, high-temperature performance, low-temperature cracking resistance, and adhesive performance of CMB was investigated by adopting various experimental tests, which including penetration, ductility, softening point, Brookfield viscosity, dynamic shear rheometer (DSR), bending beam rheometer (BBR), and bonding strength. The high-temperature stiffness and low-temperature flexibility of CMB was improved after composite modification, which in turn contributed to the shear and cracking resistance. The black diagram indicated that the formation of polymer network in the CMB improved the viscous flow resistance and maintained elastic response at high in-service temperature. The bonding strength and moisture stability of the composite bitumen-concrete interface were enhanced, with the properties exceeded the commercial SBS modified bitumen. The CMB binders R18S2 and R18S3 presented good performance and can be used for waterproofing adhesive layer as a substitute of the commercial SBS modified bitumen.

Low-temperature performance and micro-structure of warm mix recycled composite aged asphalt

Given the cold winters in Inner Mongolia, the low-temperature performance of asphalt pavement is one of the key factors affecting the service life of roads. This study focuses on commonly used SBS modified asphalt and investigates the coupling effect of adverse factors such as solar radiation, high temperature, and precipitation on road surface asphalt. The objective is offer insights for improving the applicability and service life of warm mix recycled asphalt in cold regions. By using indoor simulation aging equipment, asphalt subjected to hot oxygen aging, composite water aging, and composite ultraviolet aging was prepared to investigate the low-temperature performance of warm mix recycled asphalt. Additionally, to explore the synergistic effect of new asphalt, regenerant, and warm mix agent on the regeneration of aged asphalt, this study analyzes the low-temperature performance and microstructure changes of recycled asphalt through bending beam rheometer (BBR) test, atomic force microscopy (AFM) test, and infrared spectroscopy (FTIR) test. The results show that as the degree of aging increases, the low-temperature crack resistance performance of asphalt deteriorates. Additionally, after the regeneration of aged asphalt, the damping ratio and dissipation energy ratio of warm mix recycled asphalt slightly enhances compared to hot mix recycled asphalt. Furthermore, the incorporation of a warm mix agent enhances the asphalt’s fluidity, viscosity, surface toughness, and further its low-temperature performance. The AFM test results show that the synergistic effect of warm mix agents and regeneration effectively restores the microstructure and surface roughness of asphalt. Moreover, the warm mix agent improves the dispersion uniformity of the SBS modifier in asphalt, helping prevent the agglomeration of asphalt slurry. Qualitative and quantitative analysis of asphalt through FTIR test demonstrates that the mechanisms of warm mix agents and regeneration on new and aged asphalt are a physical process. New asphalt and regeneration supplement the internal lightweight components of aged asphalt, enabling the restoration of most asphalt without affecting the structure of SBS modified asphalt. This project provides a theoretical basis for the engineering applicability of high content warm mix recycled asphalt (composed of 50 % aged asphalt) in large temperature range areas.

Influence of preparation parameters on rheological properties and relation analysis of waste rubber modified bitumen mastic

Waste rubber modified bitumen has gained significant attention as a sustainable and innovative material in the field of pavement engineering. This study aims to evaluate the performance of rubber modified bitumen mastic by considering its rheological properties, specifically focusing on preparation parameters, i.e., rubber content, mesh number, and filler to bitumen ratio. From the experimental results, the rheological properties of rubber modified bitumen mastic were significantly influenced by preparation parameters. Increasing the rubber powder content in bitumen mastic results in higher viscosity. Increasing the rubber content improves high-temperature rutting resistance to a certain extent, however, excessive rubber powder content would result in weakened high-temperature performance improvement. The rutting factor decreases gradually with an increase in the rubber mesh number. A ratio of filler to bitumen of 0.95 exhibits the best resistance to rutting at high temperatures. Higher rubber content and larger mesh number correspond to stronger low-temperature crack resistance in bitumen mastic. As the ratio of filler to bitumen increases, the low-temperature deformation capacity gradually decreases, resulting in weaker low-temperature crack resistance. Based on the grey relation analysis, the ratio of filler to bitumen has the greatest impact on the high and low-temperature rheological properties of bitumen mastic, followed by the rubber content. The rubber mesh number has a relatively lower impact. It is crucial to control the ratio of filler to bitumen to avoid excessive values. When possible, a higher rubber powder content should be used while meeting process requirements. These findings provide valuable insights into the design and optimization of rubber modified bitumen mastic, which can contribute to the development of sustainable and high-performance bitumen mixtures, promoting the use of recycled rubber in pavement engineering.

The Impacts of Red Mud on Road Performance and Aging Resistance of Asphalt Mixture

Abstract Red mud as an asphalt modifier has been investigated in some studies, but few studies are further concerned about the effect of red mud on performance of asphalt mixture. In this study, the impact of red mud on road performance and aging endurance of asphalt mixtures was evaluated. Primarily, the optimal asphalt content was determined based on mechanical strength and volumetric properties. Then, the performance evaluations, including Marshall stability, low-temperature splitting, freeze-thaw splitting, indirect tensile fatigue, and thermal-oxidative aging, were executed. The outcomes demonstrate that in comparison with the base asphalt mixture, red mud asphalt mixture exhibits worse high-temperature stability and moisture resistance, and superior temperature shrinkage cracking resistance and fatigue performance. After the surface of red mud has been modified, the adhesion between asphalt mastics and aggregate is strengthened, and the distribution of red mud in asphalt mixture becomes more uniform, which intensifies the rigidity and road performance (except for low-temperature cracking resistance) of asphalt mixture. Furthermore, since red mud absorbs a portion of asphalt content, it can hinder the physical hardening and oxidation rate of asphalt mixture. The anti-aging ability of asphalt mixture is further reinforced by the incorporation of organic red mud.

Correlation analysis of evaluation methods and indicators for low-temperature performance of epoxy asphalt

Selecting an epoxy asphalt (EA) material with excellent low-temperature performance is a challenging task due to that the traditional test methods and indicators for thermoplastic asphalt may not be appropriate for thermosetting EA, and the binders’ low-temperature performance does not always match that of mixtures. The primary purpose of this study is to determine the appropriate low-temperature evaluation methods and indexes of EA materials and the correlation between the low-temperature performance of EA binder and EA mixture (EAM). First, the low-temperature performance of four EA binders was analyzed using tensile, bending beam rheometer (BBR), and dynamic mechanical analysis (DMA) tests. Then, the low-temperature cracking resistance of the EAMs was evaluated through beam bending and semi-circular bend (SCB) tests. Finally, Pearson correlation analysis was performed separately on the low-temperature indicators of EA binders and EAMs. Moreover, the Grey correlation analysis was employed to determine the correlation between the low-temperature properties of the two. The results showed that the correlation between fracture elongation (ε) and other test indicators was not significant. The multiple indicators of the BBR, such as viscoelastic parameters, viscous deformation ratio (JR), along with the glass transition temperature (Tg) of the DMA, showed consistent evaluation results for the low-temperature performance of the four EA binders. However, the correlation of these indicators with the cracking resistance of the EAM was notably different. The flexural strain energy density of the beam bending test and SCB fracture energies demonstrated excellent correlation. The grey correlation analysis results of these two indicators as reference series were highly similar. Specifically, the novel JR in this study and the Tg exhibited a better correlation with the low-temperature cracking resistance of EAM. These two indicators were preferentially recommended for the evaluation of the low-temperature performance of EA and the prediction of the low-temperature cracking resistance of EAM.