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To enhance the service life of traditional asphalt pavement and mitigate issues such as high-temperature rutting and low-temperature cracking, this study investigates the composite modification of matrix asphalt using thermoplastic polyurethane (TPU) and styrene-butadiene rubber (SBR). Initially, the study examines the conventional properties of the composite-modified asphalt from a macro perspective, analyzing the performance variations of asphalt before and after TPU and SBR modification. Subsequently, microscopic analysis is conducted to explore the microstructure, phase structure, and modification mechanisms of the composite-modified asphalt, with a focus on understanding the underlying reasons for performance changes. The influence of TPU and SBR on asphalt performance is evaluated comprehensively. It is found that TPU-modified asphalt demonstrates superior high-temperature performance, storage stability, and elastic recovery. Conversely, SBR-modified asphalt excels in ductility at low temperatures, though its storage stability decreases with increasing dosage. Based on a thorough analysis of the conventional properties of the two types of modified asphalt, the optimal dosages of TPU and SBR are determined to be 15% and 3.5%, respectively. In the composite-modified asphalt, TPU facilitates the even distribution of chemical components, creating a more stable cross-linked network structure. The compatibility of TPU, SBR, and asphalt contributes to the good storage stability of the composite-modified asphalt. While SBR effects physical modification, TPU induces chemical modification of asphalt. Consequently, the composite modification system benefits from both physical and chemical enhancements, resulting in excellent overall performance. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

To promote the construction of environmentally friendly, sustainable pavements and solve the impact of the scarcity of asphalt resources on highway development, bio-mixed asphalt (BMA) modified by SBS and polyphosphoric acid (PPA) was prepared, and the influence of the ratio of bio-asphalt (BA) replacing petroleum asphalt on different PPA/SBS blending schemes was explored through conventional property tests. According to each PPA/SBS blending scheme, the optimal replacement ratio of bio-asphalt was optimized, and the microstructure and distribution morphology of different PPA/SBS-modified BMA were evaluated. Conventional property test results show that with the same PPA/SBS content, the replacement ratio of bio-asphalt has a significant impact on the conventional performance of composite-modified asphalt, but the appropriate replacement ratio of bio-asphalt can improve the storage stability and conventional performance of composite-modified asphalt; in micromorphological analysis, it was found that the number of bee-like structures on the surface of the modified BMA decreased significantly, which indicated that the molecular heterogeneity of various components in the asphalt was reduced. In addition, bio-asphalt changed the particle morphology and improved the dispersity of SBS in asphalt. The composite-modified BMA had a lower SBS content, but its conventional performance was still excellent—so it has significant application prospects in road engineering. [ABSTRACT FROM AUTHOR]

Photocatalytic pavements materials are being developed to purify toxic automobile exhaust gas, especially in tunnels where the pollution concentrations are high. This study investigated the photocatalytic efficiency and pavement performance of asphalt mixtures containing steel slag and different contents of CeO2 and TiO2 as photocatalyst materials. Photocatalytic testing equipment was developed to calculate the photodegradation efficiency for CO, CO2 , NO, and HC. The pavement performance of the asphalt mixtures was evaluated using rutting tests and low-temperature bend tests. The texture depth was measured to evaluate the antislide performance. The excessive addition of the CeO2 and TiO2 nano photocatalysts had an adverse effect on the pavement performance of the steel slag asphalt mixture. The optimal contents of CeO2 and TiO2 were 7% and 0.6% by weight of the asphalt binder weight, respectively, as obtained by a gray target decision process based on principle component analysis. These findings are expected to contribute to the development of functional pavement materials that improve the surrounding air quality and have a lower environmental impact due to the use of waste slag. [ABSTRACT FROM AUTHOR]

Volatile organic compound (VOC) emissions are becoming an increasingly significant issue because of the increasing demand for bitumen in road engineering. This study attempted to develop a type of fume-suppressed bitumen with good comprehensive performance. Initially, 1, 2, and 3% organic montmorillonite and 2, 3, and 4% waxy warm-mix agents were utilised to modify bitumen. Subsequently, the fume suppression and physical and construction performances of the modified bitumen were evaluated, and the modified bitumen with the best comprehensive performance was determined. On this basis, constant- and variable-temperature heating modes were designed to verify the fuel suppression performance of the modified bitumen thoroughly. Finally, the modification mechanism of modified bitumen was investigated via atomic force microscopy. The results indicate that the modifier had the greatest impact on the ductility of the modified bitumen in terms of its physical performance. Although waxy warm mixed agents increase VOC emissions, organic montmorillonite can inhibit this effect. The modified bitumen, composed of 2% organic montmorillonite and 2% waxy warm mix agent, has the best comprehensive performance, with a 40.6% emission reduction rate under constant temperature heating mode and 46.4–28% range from 200 ℃ to 120 ℃ under another mode. The waxy warm mix agents and organic montmorillonite-modified bitumen developed into continuous and dispersed phase systems, respectively, leading to variations in the modified bitumen's physical performance and VOC emission capacity. In contrast, the composite-modified bitumen exhibited a two-phase structure with the surface morphology of an 'egg tray'. This unique structure enhances the heating surface area and facilitates heat conduction, improving the bitumen performance during construction. [Display omitted] • Consideration was given to the VOC emission reduction effect caused by the decrease in viscosity of bitumen. • The efficacy of fume suppression asphalt was verified in two heating modes. • A fume suppression asphalt with commendable comprehensive performance was designed. [ABSTRACT FROM AUTHOR]

In this study, we evaluate the flame-retardant properties of styrene-butadiene-styrene (SBS)/layered double hydroxide (LDH-) –modified asphalt. We performed physical tests, dynamic shear rheological tests, and limit oxygen index measurements to evaluate basic physical properties as well as rheological and flame-retardant properties of SBS/LDH-modified asphalt samples. Fourier transform infrared spectrometry and fluorescence microscopy were performed to elucidate the mechanism reaction between LDH and SBS-modified asphalt. In addition, a novel flame-retardant analyzer was developed and used to analyze the changes in mass and temperature during asphalt combustion. Kinetics analysis and thermogravimetry measurements were performed to determine the most probable mechanism and activation energy. The microstructure of the combustion residue was analyzed using scanning electron microscopy. The results indicate that LDH increases the viscosity of SBS-modified asphalt and its resistance to deformation at high temperatures. However, when added in high concentrations, it has a negative effect on asphalt ductility. The |G*| , G′ , and G″ values for the SBS-modified asphalt increase with the addition of LDH. However, the effect is not statistically significant over the entire investigated frequency range. Moreover, the addition of 5% LDH reduces the phase angle of SBS-modified asphalt for frequencies greater than 30 Hz. Also, its effect is not statistically significant over the entire investigated temperature range. LDH increases the nonflammable grade and activation energy of SBS-modified asphalt and results in the formation of denser char, which significantly improves its flame-retardant properties. [ABSTRACT FROM AUTHOR]

The moisture stability of an asphalt mixture was enhanced with cement, hydrated lime, and an anti-stripping agent (called AMR II) to improve the adhesive bond of asphalt with the aggregate. A total of eight asphalt binders and three aggregates (crushed gravel, limestone, and granite) were used for the preparation of different asphalt mixtures. Indirect tensile strength and residual stability tests were carried out to determine the moisture stability. The surface free energy (SFE) of the asphalt binder and aggregates were measured using the sessile drop method and universal sorption device method, respectively. Based on the SFE method, the cohesive, adhesive, and stripping energies of the asphalt and asphalt mixtures were studied. Moreover, the SFE parameters were introduced while analyzing the correlation of the cohesive, adhesive, and stripping energies of the asphalt with the moisture stability. The results show that the incorporation of a single or compound anti-stripping agent can improve the moisture stability of the asphalt mixture, and the improvement effect of compound agents is greater. Furthermore, the SFE components improved after the addition of the anti-stripping agent. The addition of the anti-stripping agent influenced the cohesive and adhesive energy remarkably, whereas the aggregate type, especially its silica content and specific surface area, has a significant effect on the adhesive and stripping energy of the asphalt mixture. A linear regression analysis suggested that the SFE parameters have a good correlation with the moisture damage properties. The SFE parameters can be used to determine the moisture damage performance, and the SFE method can be used to verify the moisture stability of asphalt mixtures. [ABSTRACT FROM AUTHOR]

This article aims to elucidate the long-term water stability of a steel slag asphalt mixture. Both chemical composition and physical morphology of the steel slag were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), the Vickers hardness test and mercury injection testing. Methods of testing wet-dry (W–D) cycles and freeze-thaw (F–T) cycles were designed, and corresponding indices were proposed. The immersion rutting test was conducted to explore the variation in rutting depth, and consequently, the long-term dynamic water coefficient Kl was proposed to analyze the resistance to dynamic water flushing. A regression model was used to analyze the relationship between steel slag content and long-term water stability. Finally, the long-term corrosion characteristics of the steel slag asphalt mixture were analyzed by SEM. The results show that the addition of steel slag can improve the long-term water stability of the asphalt mixture. The water stability of the steel slag asphalt mixture declines with increasing W–D and F–T cycles. The degradation trend becomes gentle after 6 W–D cycles. The attenuation of the water stability of the mixture slows after 15 F–T cycles. The long-term water stability of the steel slag asphalt mixture was evaluated by comparing the residual stability after 6 W–D cycles (MS6) and the tensile strength ratio (TSR) of the steel slag asphalt mixture after 15 F–T cycles (TSR15). The Kl value of the steel slag asphalt mixture first increases and then decreases with increasing steel slag content, and the best effect in terms of long-term dynamic water corrosion resistance is observed for a 30% steel slag asphalt mixture. The SEM results show that, for steel slag asphalt mixture water damage, the steel slag hydrates and produces microcracking on the surface. [ABSTRACT FROM AUTHOR]

Moisture susceptibility plays an important role in the damage of asphalt pavement. Failure occurs when asphalt is removed from the aggregate particles due to the decreased adhesion between the asphalt and aggregate in comparison with that between water and the aggregate. In recent years, efforts utilizing nanomaterials to improve the diverse properties of asphalt have proven to be effective. In this study, three types of nanoclays were used to modify styrene-butadiene-styrene- (SBS-) modified asphalt. The resistances to water damage of the modified binders were evaluated using the surface free energy (SFE) and atomic force microscopy (AFM). The results revealed that the total SFE decreased and the energy ratio (ER) increased when the asphalt binder was modified with the nanoclays, indicating that the addition of nanoclays can improve the moisture resistance of these aggregate-binder systems. After immersion, a decreased amount of bee structures was observed in both the SBS and nanoclay-modified asphalts due to the interactions between water and bitumen. However, the residual amount of bee structures was higher in the nanoclay-modified asphalts than in the SBS-modified asphalt, indicating that the addition of nanoclay makes the surface morphology of asphalt more resistant to water damage. Finally, freeze-thaw splitting tests were used to verify the results obtained through the SFE and AFM tests. [ABSTRACT FROM AUTHOR]

Steel slag, an industrial by-product of steel industry, has great potential in asphalt mixture as an alternative aggregate. The use of steel slag can reduce environmental pollution effectively. Meanwhile, rubber asphalt also has good eco-friendly performance. To study the adhesion between steel slag and rubber asphalt, pull-out test and net adsorption test were utilized to evaluate the adhesion between different aggregates and rubber asphalt. The morphology of different aggregates and the microstructure of aggregate-asphalt interface transition zone were observed using scanning electron microscopy (SEM). Moreover, Fourier Transform Infrared (FTIR) Spectrometer was applied to study the chemical reaction mechanism between steel slag and rubber asphalt. The results show that the adhesion property between steel slag aggregate and rubber asphalt is higher than that between diabase and rubber asphalt. The results of net adsorption and SEM test demonstrated the porous structure of steel slag can improve the adhesion between the steel slag and asphalt effectively. In addition, FTIR test results demonstrated there exists chemical reaction between steel slag and asphalt, contributing to the enhancement of the adhesion property between asphalt and steel slag aggregate. [ABSTRACT FROM AUTHOR]

The objective of this study was to investigate the rheological properties and modification mechanism of crumb rubber modified asphalt (CRMA) with different reaction parameters. The test results indicate that the high reaction temperature can increase the rutting resistance but decreases the temperature stability of CRMA. At low reaction temperature, there is mainly swelling reaction in CRMA. However, the rubber particles begin to degrade in high temperature condition. The results can be confirmed by Fourier infrared spectroscopy (FTIR) and LMS tests. The LMS was well correlated with the rheological properties. The LMS may provide a simple means to determine the mechanical properties of binders. [ABSTRACT FROM AUTHOR]

To evaluate sensitivity of moisture damage resistance with chemical composition of asphalt, the adhesion energy, debonding energy as well as compatibility ratio of 69 asphalt-aggregate combinations were calculated with thermodynamical models. Pearson correlation analysis and regression analysis were carried out to correlate the relationships between asphalt chemical composition (saturates, aromatics, resins, asphaltenes, and wax) and moisture stability of asphalt mixture. The results showed that more resins and less asphaltenes in asphalt could lead to better moisture stability of asphalt mixture under dry and wet conditions, which can be effectively predicted by multiple regression models with different asphalt chemical components. [ABSTRACT FROM AUTHOR]

Styrene-butadiene-styrene (SBS) modified asphalt used in road engineering is a complicated mixture of various compositions. The present study was undertaken to evaluate the influence of different raw materials and their content on the moisture stability of SBS copolymer modified asphalt mixture. A total of 18 different combinations of base asphalt, SBS, furfural extract oil (FEO), and stabilizer were considered to prepare different SBS modified asphalt samples, and the contact angle test was carried out to determine the work of adhesion and the work of debonding of SBS modified asphalt with aggregate. Moreover, a multi-factor Analysis of Variance (ANOVA) was conducted to investigate the statistical effects of the material composition factors. The results show that the bond strength between SBS modified asphalt and aggregate is significantly affected by the source of base asphalt, but it is insensitive to the change of SBS type under dry and wet conditions. Besides, the moisture damage resistance of SBS modified asphalt improves firstly and then reduces with the rising storage of SBS, FEO, and stabilizer. Furthermore, linear regression analysis suggests that the work of adhesion under dry condition has excellent correlation with the work of debonding under wet condition. [ABSTRACT FROM AUTHOR]

[Display omitted] • The aging behavior of PPA/SBS modified bio-mixed asphalt was analyzed. • The effect of aging on chemical composition of PPA/SBS modified asphalt was investigated. • The PPA/SBS modified bio-mixed asphalt has batter elastic response. • The bio-asphalt has a certain positive effect on aging behaviour. This study investigates the performance of polyphosphoric acid/styrene–butadienestyrene (PPA/SBS)-modified bio-mixed asphalt after thermo-oxidative and ultraviolet (UV) aging, based on its high-temperature rheological properties and microscopic characteristics. The temperature sweep test results revealed that long-term thermo-oxidative aging significantly increased the dynamic shear moduli of the composite-modified asphalts, where the maximum increment in composite-modified asphalts reached to 425 %. However, the dynamic shear modulus of the composite-modified asphalt decreased owing to the degradation of aromatic aldehydes to fatty aldehydes after ultraviolet aging, leading to softer composite-modified asphalts. In addition, the multiple-stress creep recovery (MSCR) test revealed that the maximum increment in the recovery rate of composite modified asphalt reached to 37.4 %. Moreover, the increasing rate of J nr was significantly lower than that of the control asphalt after long-term aging, particularly at a stress level of 3.2 kPa. Finally, the microstructures of each asphalt sample before and after aging were observed using atomic force microscopy. The surface morphology of the composite modified asphalt after aging was relatively smoother, indicating that the molecular homogeneity of the aging residue of the composite-modified asphalt sample was better than that of the control asphalt sample. [ABSTRACT FROM AUTHOR]

• The mechanical properties of BA/PPA/SBS composite modified asphalt were studied. • The chemical composition of composite modified asphalt was analyzed. • The interaction mechanism between BA, PPA, SBS, and petroleum asphalt was discussed. To promote the application of environmentally-friendly and sustainable bio-asphalt (BA) in road engineering, polyphosphoric acid (PPA) and styrene–butadienestyrene (SBS) were used to prepare BA/PPA/SBS composite modified asphalt. The mechanical properties of composite modified asphalt and the interaction mechanism of each modifier were investigated through conventional property, rheological property, infrared spectroscopy, fluorescence microscopy test, and gravimetry analysis for SARAs fractions. The conventional property test results show that PPA and BA improve the storage stability of SBS modified asphalt, and the composite modified asphalt with lower SBS content still has excellent performance. The rheological property test results show that the decrease of SBS content has negative effect on the rheological property of asphalt. But in general, the composite modified asphalt has good high-temperature deformation resistance. The IR-spectra of BA before and after reacting with PPA indicates that the chemical composition of the BA in this study was mainly sugar alcohols, and the esterification reaction occurred during reaction with PPA. By comparing the fluorescence images, it was found that the BA significantly improve the dispersion and compatibility of SBS particles in asphalt. The SARAs fractions analysis shows that the composite modified asphalts have higher content of asphaltenes and aromatics. [ABSTRACT FROM AUTHOR]

Asphalt pavements are widely used in road engineering owing to their good skid resistance, ease of maintenance, and high driving comfort. However, large amounts of toxic fumes are produced during petroleum asphalt heating, asphalt mixture preparation, and pavement construction. This review clarifies the fuming mechanisms and hazards of asphalt fumes with the aim of promoting the application of fume-suppression asphalt(s) and reducing the emission levels of asphalt fumes. First, starting from the fuming mechanisms of hot asphalt, the composition and hazards of asphalt fumes are described. Second, existing indoor and on-site asphalt fume testing methods are discussed. Finally, the inhibitory effects and mechanisms of different types of fume suppressants are discussed separately to provide a reference for the popularization and application of fume-suppression asphalt. The review shows that the existing descriptions of the fume-generation mechanisms are based on physical phenomena, and there is a lack of systematic research at the chemical level. An indoor asphalt fume test is usually conducted using a fume-generation and collection device, where the main test object is an asphalt binder. Therefore, it is difficult to simulate real fuming conditions in these tests. A field testing mainly evaluates the concentrations of different types of asphalt fumes, and there is a lack of standardization of asphalt fume test methods and emission specifications. Existing asphalt fume suppressants mainly include polymers, flame retardants, warm mixing agents, adsorbents, and nanomaterials; traditional fume suppressants such as polymers, flame retardants, and warm mix agents have poor fume-suppression effects or reduce the pavement performance. Meanwhile, nanomaterial-based fume suppressants have good fume-suppression and improved pavement performance to some extent; however, they are still in the early stages of exploration. Therefore, future research should focus on asphalt fume-generation mechanisms, asphalt fume-evaluation methods and specifications, and environmentally friendly nanomaterial-based fume suppressants. [Display omitted] • The asphalt fuming mechanism in different construction stages were summarized. • The test methods of asphalt fume were discussed in detail from the perspective of indoor test and field test. • The inhibitory effect, mechanism and working performance of different fume suppressants were classified and summarized. [ABSTRACT FROM AUTHOR]

• Asphalt mixtures contained ATH and MMT were evaluated by CONE test. • Road performance of the ATH/MMT asphalt mixtures was investigated. • ATH/MMT composites show good flame retardant and smoke suppression properties in asphalt mixture. Alumina trihydrate (ATH) and organic montmorillonite (MMT) were used to improve the flame retardancy and smoke suppression properties of highway tunnel asphalt mixture. A series of laboratory tests were conducted on asphalt mixtures to evaluate the effects of ATH/MMT composites on their combustion properties and road performance. Cone calorimeter test results indicate that ATH/MMT delays the ignition time of the asphalt mixture and reduce the total and peak heat release rate of asphalt mixture, thus significantly improving the flame retardancy and smoke suppression properties. The road performance test results show that ATH/MMT additionally improves the deformation resistance, moisture damage resistance, fatigue life and temperature segregation resistance of the asphalt mixture. Although the low- temperature crack resistance of the asphalt mixture is slightly reduced, it still satisfies road performance requirements. [ABSTRACT FROM AUTHOR]

• A new equipment for dynamic flame retardant performance of asphalt materials was designed. • Effect of ATH/OMMT on flame-retardant and smoke-suppression properties of asphalt was studied. • The synergistic flame retardant mechanism of ATH/OMMT composite modified asphalt was revealed. To investigate the flame-retardant performance and mechanism of aluminum hydroxide–organic montmorillonite(ATH/OMMT) composite modified asphalt, the limiting oxygen index test(LOI) and scanning electron microscopy(SEM) were used. In addition, new dynamic flame-retardant test equipment for asphalt was designed. The results show that the ATH/OMMT composite modified asphalt has excellent flame-retardant performance. The dynamic combustion characteristics of asphalt were divided into four stages. ATH/OMMT can delay ignition time, increase ignition temperature, and reduce heat release during combustion. Both ATH and OMMT work together to improve the strength and compactness of the composite modified asphalt carbon layer, thereby improving its flame-retardant properties. [ABSTRACT FROM AUTHOR]

• Effect of OMMT on flame-retardant and smoke-suppression properties of asphalt was studied. • An equipment was designed to characterize the dynamic flame-retardant property of asphalt materials. • The flame-retardant mechanism of OMMT modified asphalt was also investigated. • The flame-retardant and smoke-suppression mechanism model of OMMT modified asphalt was established. To investigate the performance and mechanism of flame retardance and smoke suppression of organic montmorillonite (OMMT) modified asphalt, limiting oxygen index (LOI) and dynamic flame-retardant performance tests were performed. The pyrolysis characteristics of modified asphalt were analyzed using thermalgravimetric-Fourier transform infrared (TG-FTIR) analysis. The results show that the OMMT particle size has little effect on modified-asphalt performance. OMMT increases the ignition time and ignition temperature, and it reduces heat release during combustion. OMMT also significantly inhibits smoke emission during pyrolysis and combustion of modified asphalt. Finally, a flame-retardant and smoke-suppression mechanism model of OMMT-modified asphalt was established. [ABSTRACT FROM AUTHOR]

• The effect of thermal aging on the mechanical properties of ACRMA was evaluated. • The reaction mechanism of ACRMA before and after aging was investigated. • Microwave activation of crumb rubber improved the anti-aging properties of asphalt. The anti-aging properties and related mechanism of microwave-activated crumb rubber-modified asphalt (ACRMA) were evaluated in this study. Physical and rheological tests were conducted on ACRMA before and after simulated thermal aging, and several microcosmic tests were performed to analyze the aging mechanism. The stiffness, plasticity, and viscoelasticity of ACRMA were less affected by aging than crumb rubber-modified asphalt (CRMA). After aging, ACRMA exhibited better high-temperature performance and permanent deformation resistance than CRMA. The thermal aging process of ACRMA was analyzed, and the anti-aging mechanism model was established. The anti-aging performance of ACRMA was better than that of CRMA. [ABSTRACT FROM AUTHOR]

• Effect of ATH and OMMT on flame retardancy properties of asphalt was studied. • VOCs emission properties of asphalt mixture in mixing process was investigated. • The thermal stability and dynamic volatiles release properties of the asphalt binders were analyzed. • Effect of ATH/OMMT composites on engineering performances was evaluated. The objective of this study was to evaluate the flame retardancy and emission properties of asphalt binders containing ATH and OMMT. Limit oxygen index test was performed to evaluate the flame retardancy of each asphalt binder. Volatile organic compound (VOC) emission properties of the asphalt mixture in the mixing process were investigated using a designed test method. Thermogravimetry and Fourier transform infrared spectroscopy were used to evaluate the thermal stability and volatile-release properties of the asphalt binders. The results indicated that both ATH and OMMT effectively suppress the VOC release of the modified asphalt. The flame retardancy and VOC-emission properties of the OMMT/ATH modified asphalt were significantly improved. The addition of ATH/OMMT delayed the thermal decomposition and exhibited good thermal-insulation performance, reducing the heat release during asphalt combustion. Additionally, The ATH/OMMT compounds prevented the breakage of molecular chains in the asphalt, promoting the charring of the asphalt during combustion. According to the engineering-property tests of modified asphalt mixtures, the ATH/OMMT significantly improved the high-temperature performance of the asphalt mixture. However, it slightly reduced the thermal-cracking resistance and moisture susceptibility of the asphalt mixture. [ABSTRACT FROM AUTHOR]

Waste crumb rubber (CR) can be used in asphalt pavement construction to develop eco-friendly and sustainable pavements. The objective of this study was to investigate the reaction mechanism, high-temperature properties, thermal stability, and volatiles released by CR-modified asphalt (CRMA) activated using microwaves (i.e., ACRMA). The chemical characteristics determined via Fourier-transform infrared spectroscopy revealed that mainly physical reactions occurred in the CRMA before and after activation; however, the swelling reaction in the ACRMA was more efficient than that in the CRMA. These results were confirmed by gel permeation chromatography and atomic force microscopy. The high-temperature performance of the ACRMA was slightly better than that of the CRMA. Additionally, according to stress creep and recovery test results, the microwave activation reduced the stress sensitivity of the rubber-modified asphalt. Thermogravimetric curves indicated that the microwave activation reduced the decomposition temperature of the rubber-modified asphalt. Moreover, the total amount of released volatiles for the base asphalt was significantly larger than that for rubber-modified asphalts, indicating that the CR suppressed the total amount of released volatile gases from the asphalt during the pyrolysis of asphalt. But the addition of CR can increase the release of some toxic gases in CRMA and increase the toxicological potential of asphalt fumes. However, in the initial pyrolysis of rubber asphalts, microwave treatment can reduce the generation of toxic gases. In the later stages of this process, the introduction of rubber particles before and after activation has little effect on the released volatiles. [ABSTRACT FROM AUTHOR]

Effective approaches are required to be developed to solve the poor compatibility and thermal stability problems of crumb rubber-modified asphalt (CRMA). This study focuses on a method called microwave activation. However, seldom researches pay attention to the properties of MACRMA after aging. The objective of this study was to prepare microwave-activated CRMA (MACRMA) and investigate the performance of asphalt after aging. The samples were subjected to thin-film oven test (TFOT) at different times and temperatures. The effect of heat aging on the properties of MACRMA was evaluated by three indicator tests: viscosity, dynamic shear rheology test (DSR), and repeat creep recovery test (RCRT). The test results indicated that the MACRMA after two aging conditions had noticeably lower performance values (e.g., penetration, ductility) compared to unaged samples, and thus, the need to control temperature and time for mixing and construction was verified to be important. In addition, the G*/sin δ and phase angle values were largely influenced by the TFOT aging temperature and time. The MACRMA's ability to recover was improved after aging. Compared with the aging temperature, the aging time had a more significant effect on the deformation and recovery ability of MACRMA. [ABSTRACT FROM AUTHOR]

[Display omitted] • The micro modification mechanism of bio-asphalt/TLA modified asphalt are analyzed. • Bio-asphalt improves the low temperature performance of TLA modified asphalt. • The relationship between indexes of modified asphalt and mixture is established. Trinidad Lake Asphalt (TLA) modified asphalt has excellent high temperature performance, but its low temperature performance is poor, which limits its engineering application. But bio-asphalt presents relatively excellent low temperature performance. In this paper, TLA and Bio-asphalt were used as additives to prepare composite modified asphalt with excellent properties both at high and low temperatures. The micro modification mechanism of asphalt was studied by Fourier transform infrared spectroscopy (FTIR) and gel permeation chromatography (GPC). The macro mechanical behavior of asphalt binder was explored through routine physical property test and rheological property test. Finally, the mechanical properties of asphalt mixture were studied through the routine test of asphalt mixture, and the relationship between the macro and micro indexes of asphalt binder and the high and low temperature performance of asphalt mixture was established through grey correlation. The test shows that the mixing mode of TLA, bio-asphalt and base asphalt is physical blending. Modifiers affect the macro mechanical properties of asphalt by changing the distribution of asphalt components, the size of molecular weight, the interaction strength and arrangement of molecules. TLA improves the performance of asphalt binder at high temperature, but weakens the low-temperature performance. The low temperature performance of TLA modified asphalt was significantly improved by adding bio-asphalt at the cost of slightly reducing the high temperature performance. When the content of bio-asphalt is 9%–12%, the bio-asphalt/TLA modified asphalt and its mixture have better performance on high and low temperature properties than that of base asphalt. The micro indexes such as aromatic ring index and weight average molecular weight are good indicators of the high temperature performance of asphalt mixture. Creep rate (m), equivalent brittle point (T1.2) and stiffness modulus (S) can reflect the low-temperature performance of asphalt mixture. [ABSTRACT FROM AUTHOR]

This study proposes the incorporation of waste steel slag and waste rubber into asphalt to prepare asphalt mastic with increased mechanical properties and can thus concurrently limit environmental pollution from these wastes. The surface of crumb rubber (CR) was activated by NaClO and was then treated with KH550 silane coupling modifier. Dynamic shear rheometer (DSR), multi-stress creep recovery (MSCR) and zero shear viscosity (ZSV) tests were applied explore the high temperature performance of asphalt mastic. The performance of asphalt mastic was analyzed by Burgers model, and the enhancement mechanism was analyzed by Fourier transform infra-red (FTIR) spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray (EDX), fluorescent microscopy (FM), and X-ray diffraction (XRD). Experimental results showed that coupling modified CR improved the complex modulus (G*) and rutting factor (G*/sinδ) and reduced the temperature sensitivity of asphalt mastic. The coupling modified CR increased the elasticity coefficient E 1 , viscosity coefficient η 1 , relaxation time η 1 /E 1 and delay time η 2 /E 2 of asphalt mastic by 2.8 times, 3.6 times, 1.3 times and 0.9 times, respectively, while steel slag powder (SSP) further enhanced the mechanical properties of the asphalt mastic. FM test showed that coupling modifier CR promoted the swelling of CR and SBS polymer, and hence resulted in a well-developed cross-linked network structure in the asphalt. The positive effect of SSP on the high temperature properties of asphalt mastic suggests that the use of SSP and CR in pavement engineering provides a sustainable solution for the disposal of industrial wastes and the preparation of new asphalt mastic with higher mechanical and thermal properties for practical applications. [Display omitted] • The crumb rubber was modified by secondary treatment. • Burgers model was used to analyze the viscoelastic behavior of asphalt mastic. • The feasibility of CR with steel slag powder in road engineering was demonstrated. • Coupling modified CR promoted the network structure in modified asphalt mastic. • A sustainability analysis of the application of CR and SSP in asphalt was performed. [ABSTRACT FROM AUTHOR]

[Display omitted] • MD simulation revealed anti-freezing mechanism of AFP-modified emulsified asphalt. • Microscopic properties of AFP-modified emulsified asphalt were observed. • Rheology and frost resistance of AFP-modified emulsified asphalt studied. • MD simulations were consistent with microscopic and freeze resistance test results. In this study, biological modification technology was utilized to improve the frost resistance of pavement. By adding biological antifreeze protein to asphalt-based materials, a biomodified emulsified asphalt layer with active antifreeze qualities was created. The mixing mode and its anti-freezing efficacy were investigated using molecular dynamics (MD) simulations. The anti-freezing protein (AFP) was embedded on the asphalt surface, and the structure was completed with asphalt application in two phases. After AFP was attached to the surface of the asphalt binder, the structure remained stable at low temperatures, inhibiting icing and producing a thermal hysteresis differential. Hydrogen bonding and Van der Waals forces influence ice molecule aggregation, and AFP can reduce their effect and induce ice crystal melting. Scanning electron microscopy (SEM) and fluorescence microscopy (FM) revealed that the AFP surface was uneven and anchored to the asphalt surface. The overall structure was complete, with a two-phase distribution that corresponded with the MD results. The anti-icing test results demonstrated that the AFP-modified emulsified asphalt coating effectively inhibited ice condensation and could change the ice crystal growth pattern. The rheological test results revealed that AFP had a slightly negative effect on the high-temperature deformation resistance of the asphalt binder. Environment friendly AFP-modified emulsified asphalt can significantly improve the anti-freezing characteristics of the pavement. [ABSTRACT FROM AUTHOR]

[Display omitted] • Bio-antifreeze protein is used to prepare pavement anti-freezing coating. • The anti-freezing performance of bio-AFP-modified emulsified asphalt coating was tested. • The road performance of bio-AFP-modified emulsified asphalt coating was tested. Natural organisms use their own biological antifreeze proteins (AFP) to cope with cold environments. Based on this natural phenomenon, we herein use biological AFP and asphalt-based materials to prepare road anti-icing coating materials and subsequently study its storage stability and anti-icing performance. The storage stability test, fluorescence microscope analysis, scanning electron microscope analysis, and infrared spectrum analysis demonstrated that when the AFP powder content was not more than 5%, it was evenly dispersed in the emulsified asphalt, had good stability, did not undergo a chemical reaction, and retained the molecular activity of AFP. Combined with the anti-icing, pull-out, and falling ball impact tests, the addition of biological AFP powder demonstrates obvious anti-icing performance; furthermore, with an increase in the powder content, the anti-icing effect is improved. The road performance test showed that the coating had good durability and spalling resistance. When the spraying amount of the coating on the asphalt pavement is ≤ 0.4 kg/m2, the BPN value and TD value meet the requirements of the specification. The application of a biological AFP-modified emulsified asphalt coating can significantly improve the anti-icing performance of roads and does not harm ecological environments. [ABSTRACT FROM AUTHOR]

[Display omitted] • The virgin-old recycling slowed the thermal-oxidative aging by physical approach. • The change in molecules affects the viscosity more than the fatigue performance. • The increase in viscosity was mainly attributed to macromolecules weight increased. • The proportion of the dispersion medium affected the fatigue resistance potential. This study aimed to investigate the thermal-oxidative aging and virgin-old recycling behavior of SBS polymer modified asphalt. For the same, the four-component method, the Fourier transform infrared spectroscopy (FTIR), and the gel permeation chromatography (GPC) test were adopted for characterizing five types of asphalt binders. Besides, Brookfield rotary viscosity and time scan tests were conducted for measuring the rheological parameters of the asphalt samples. The results indicated the following: (i) Thermal-oxidative aging deteriorated the fluidity and performance stability of the asphalt. The aromatic ring index, I C=C , was able to reflect the change in the temperature sensitivity of the asphalt during the process of aging. (ii) After thermal oxidation, the increase in viscosity was mainly attributed to the increase of asphalt macromolecules weight. A reduction in the proportion of the dispersion medium in the asphalt colloid structure was observed to be the main reason for its decreased fatigue resistance potential. (iii) By adding fresh asphalt, the virgin-old recycling approach slowed the thermal-oxidative aging, primarily due to physical integration. (iv) In this study, the asphalt viscosity-temperature properties were more sensitive to molecular changes than fatigue properties. [ABSTRACT FROM AUTHOR]