Performance Of Asphalt Research Articles

High-Temperature Characteristics of Polyphosphoric Acid-Modified Asphalt and High-Temperature Performance Prediction Analysis of Its Mixtures

To promote the application of economical and sustainable polyphosphoric acid (PPA)-modified asphalt in road engineering, styrene-butadiene block copolymer (SBS), styrene-butadiene rubber (SBR), and PPA were used to prepare PPA/SBS and PPA/SBR composite-modified asphalts, which were tested and the data analyzed. Fourier transform infrared spectroscopy (FTIR) tests and thermogravimetric analysis (TG) tests were carried out to study the modification mechanisms of the composite-modified asphalts, and the high-temperature performance of the PPA-modified asphalt and asphalt mixtures was analyzed by dynamic shear rheology (DSR) tests and wheel tracking tests. A gray correlation analysis and a back-propagation (BP) neural network were utilized to construct a prediction model of the high-temperature performance of the asphalt and asphalt mixtures. The test results indicate that PPA chemically interacts with the base asphalt and physically integrates with SBS and SBR. The PPA-modified asphalt has a higher decomposition temperature than the base asphalt, indicating superior thermal stability. As the PPA dosage increases, the G*/sinδ value of the PPA-modified asphalt also increases. In particular, when 0.6% PPA is combined with 2% SBS/SBR, it surpasses the high-temperature performance achieved with 4% SBS/SBR, suggesting that PPA may be a good alternative for polymer modifiers. In addition, the creep recovery of PPA-modified asphalt is influenced by the stress level, and as the stress increases, the R-value decreases, resulting in reduced elastic deformation. Furthermore, the BP neural network model achieved a fit of 0.991 in predicting dynamic stability, with a mean percentage of relative error (MAPE) of 6.15% between measured and predicted values. This underscores the feasibility of using BP neural networks in predictive dynamic stability models.

Effect of Binary Blended Fillers on the Durability Performance of Recycled Cold-Mix Asphalt

Cold-mix asphalt is a greener alternative to pavement construction, processed at 10–40 °C, which is typically lower than other techniques like warm-mix asphalt and hot-mix asphalt. Huge amounts of construction and demolition waste, such as broken bricks, recycled concrete aggregates, reclaimed asphalt pavement, ceramic waste, etc., are generated every year due to the acceleration in infrastructure development. The production of such massive amounts causes landfilling issues, and their disposal is a serious issue nowadays. This study examines the effect of binary blended fillers on the performance of cold asphalt mixes using emulsified binders and 50% reclaimed asphalt pavement materials. Moreover, three types of binary blended fillers (BBFs), cement, fly ash, and Stabil Road, were used at different dosages. Overall, 500 samples were prepared for the mix design, and the optimum emulsion content was determined as 11% and 9% for the CM and 50R mixes, respectively, based on the Marshall stability peak value and volumetric properties such as voids in the mineral aggregates, total voids, and dry density. The moisture susceptibility of the recycled cold-mix asphalt (RCMA) mixture was evaluated using the tensile strength ratio. Cantabro abrasion loss was used to assess the cohesion resistance of the mixtures. The dynamic response of the mixes to the applied load was evaluated using the resilient modulus. The results of the present study reveal that using BBFs in the RCMA improved the inter-particle bonding and strength. Furthermore, BBF incorporation enhanced the performance of the recycled cold-mix asphalt.

Performance Characteristics of Nano Palm Shell Ash (NPSA) in Asphalt Mixture

One innovation in creating new materials that have superior properties compared to large-sized materials is to use nanotechnology. The uniqueness of nano materials is that the smaller the size of the material, the greater the surface area and performance characteristics of the material in the asphalt mixture. This research develops nano technology in asphalt pavement construction by making nano material from palm shell ash waste. The aim of this research is to determine the effect of adding palm shell ash nano material as a substitute for asphalt in the AC-WC mixture. The research method was carried out by testing the morphological characterization of the palm shell ash nano material using X-Ray Fluorescence (XRF) testing and Scanning Electron Microscope (SEM) testing, then continuing with testing the characteristics of the mixture using the Marshall testing method. The nano material used is palm shell ash material obtained from palm shell burning waste originating from Riau which is then processed into Nano Palm Shell Ash (NPSA) material using a ball mill. The asphalt used is Pen 60/70 asphalt produced by Pertamina. The use of NPSA material in asphalt modification with NPSA variations of 1%, 2% and 3% can improve the performance of marshal characteristics compared to conventional asphalt mixtures. It can be seen that the stability, flow, VFA and MQ values increase with increasing NPSA percentage in asphalt. Meanwhile, the VIM and VMA values decreased along with the increase in the NPSA percentage in asphalt. In addition, increasing the percentage of NPSA in asphalt can reduce the use of optimum asphalt content compared to conventional asphalt mixtures. Utilizing palm shell ash waste is the best alternative for improving the performance of asphalt in mixtures and is environmentally friendly and economical.

Effect of SARA Fractions on Fatigue Properties of Hard Asphalt.

The fatigue performance of hard asphalt is an important factor that affects the service life of asphalt pavement. In order to comprehensively explore the influence of chemical components on the fatigue performance of hard asphalt, and to eliminate the chemical instability between the microstructure of asphalt from different oil sources, seven kinds of hard asphalt were designed and prepared with saturates, aromatics, resins, and asphaltenes (SARA) extracted from the same hard asphalt. Rheological, time sweep and linear amplitude sweep (LAS) tests were carried out to evaluate the fatigue properties. The results show that the complex modulus of asphalt binds increased rapidly with an increase of asphaltene and resins and that the colloidal structure was strengthened, which would increase the fatigue factor. In the time sweep test, the strength of the colloidal structure significantly affected the fatigue life, and the fatigue life was different under different test stresses. In the viscoelastic continuum damage (VECD) model, the cumulative damage was related to the modulus, while with the increase of asphaltene and resins, the fatigue life showed a trend of first increasing and then decreasing. The linear regression analysis showed that the fatigue life of hard asphalt had a good correlation with strain sensitivity. This study investigated the applicability of different fatigue evaluation methods and revealed the influence of four components on the fatigue properties of hard asphalt. The results provide significant insights in the improvement of the fatigue performance of both hard asphalt and corresponding mixtures.

Effect of surfactant modified phosphogypsum whisker on service performance of asphalt based on multi-scale experiments

The development of modern chemical technology had inevitably produced massive phosphogypsum (PSP), the accumulation and storage of PSP had caused serious economic losses and environmental pollution. As the secondary refining product of PSP, the application of phosphogypsum whisker (PSW) to asphalt pavement not only effectively mitigated the adverse impact of PSP on the economy and environment, but also promoted the resourceful utilization of solid waste. However, since PSW was an inorganic material, it was difficult to fuse well with asphalt. Therefore, to enhance the compatibility of PSW with asphalt, this study investigated the modification process of PSW by using four surfactants to modify PSW with organic coating. The effect of surfactants on the surface activity of PSW was evaluated by relevant tests, and the surface enhancement modification mechanism and microstructure of surfactants on PSW were investigated, and then the effect of surfactant-modified PSW (MPSW) on the service performance of asphalt was evaluated. The results showed that the surfactant covered the surface of PSW by intermolecular forces and chemical bonding, which enhanced the surface activity of PSW. The compatibility of PSW with asphalt was enhanced by surfactant, and the MPSW 10599was just physically blended with virgin asphalt. Although the brittleness of virgin asphalt was enhanced to a certain degree by MPSW, the thermophysical properties of virgin asphalt at low temperature was significantly improved, and the incorporation of MPSW enhanced the thermal stability and flame retardancy of virgin asphalt. The incorporation of MPSW would slightly increase the viscosity of virgin asphalt, but the viscous activation energy was reduced and the temperature sensitivity was improved. Furthermore, the low temperature performance of virgin asphalt was improved to a certain degree with the incorporation of MPSW, while the improvement effect was not significant once the temperature was close to the glass transition temperature. Finally, combined with the relevant test results, the recommended dosage of MPSW in asphalt was 10% in this study, and the surface modification of PSW by surfactant was a multifunctional method of powder modification.

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.

Quantitative characterization of fusion state of virgin and aged asphalt using nano-ferrous ferric oxide tracer

The exact evaluation of the fusion rate of virgin and aged asphalt is essential to optimize the performance of the recycled asphalt mixture. The fusion rate index was developed by tracing the distribution of tracer asphalt, which contains nano-ferrous ferric oxide (nano-Fe3O4) tracer. Laboratory fusion simulation tests were performed on three types of asphalt to obtain different fusion states, and fatigue tests were performed to evaluate the influence of the fusion rate on the fatigue life of the recycled asphalt. It was found that the tracer asphalt containing 4% nano-Fe3O4 shows the optimal trace effect, and the developed fusion rate index can quantitatively characterize the influence of different factors on the fusion state of the recycled asphalt. The fusion state is closely related to the fatigue performance of recycled asphalt, and the fusion rate index can fairly evaluate its fatigue performance. The relationship between the fusion rate and the fatigue life of recycled asphalt depends on the factors that cause the fusion rate variation. Under the influence of the amount of rejuvenator, the fatigue life of recycled asphalt grows exponentially with increasing fusion rate due to enhancement of molecular motion as well as a supplement of lightweight components. Under the influence of heat preservation treatment, fatigue life increases linearly with increasing fusion rate. The proposed fusion rate index can be utilized to quantitatively characterize the fusion state of virgin and aged asphalt, thus providing a simple way to guide the practical application of recycled asphalt.

Mechanical performance of cold mix asphalt containing cup lump rubber as a sustainable bio-modifier

The road construction industry aims to contribute to the protection of already compromised environment. Cold mix asphalt (CMA) is a measure initiated by the road industry to protect the environment and preserve energy. Despite having additional benefits, CMA has attracted little attention due to its inferior performance. CMA's performance is enhanced using a sustainable binder bio-modifier, natural cup lump rubber (CLR) is one of them. This study evaluated the tensile properties, rutting, moisture susceptibility, and adhesion properties of CLR-modified CMA (CMA-CR). The tensile property was enhanced by 26% due to CLR modification. CMA-CR had excellent rutting resistance of less than 2 mm rut depth at 10,000 load cycles, showing 70% improvement compared with conventional CMA. Moisture susceptibility evaluation indicated that CMA-CR had tensile strength ratio (TSR) value of 104%, satisfying the minimum 80% requirement of AASHTO T283. It also retained more than 96% bitumen coating. The moisture damage resistance was improved by 12% and 10% in terms of TSR and stripping, respectively. The durability results revealed that the CMA-CR mixture prevented higher mass loss, representing 14% improvement compared with conventional CMA.

Microbial treatment of waste crumb rubber: Reducing energy consumption and harmful emissions during asphalt production process

The emergence of crumb rubber modified asphalt (CRMA) has promoted the recycling utilization of waste tires and the improvement of asphalt performance. However, its unsatisfactory storage stability and high construction temperature have brought about excessive energy consumption and environmental challenges. In this study, the waste crumb rubber (CR) was bio-desulfurized by the synergy between two types bacteria for 7 days and 14 days, respectively. On this basis, bio-desulfurization crumb rubber modified asphalt (BCRMA) was prepared. The desulfurization effect of CR was characterized. Thermal storage stability and environmental performance of BCRMA were mainly investigated. The results showed that bio-desulfurization increased the number of pores, surface roughness and specific surface area of CR, and decreased the content of sulfur element. Bio-desulfurization of CR improved the insufficient thermal storage stability of rubberized asphalt and reduced the risk of system segregation. Bio-desulfurization CR has been proven to be a promising environmentally friendly material that can effectively lower the release concentration and release type of harmful flue gas from CRMA. This study makes the large-scale promotion and application of CRMA possible.

Effect of steel slag and aspha-min zeolite on moisture susceptibility and stiffness of asphalt concrete mixes

This study evaluates the laboratory performance of Warm-Mix Asphalt (WMA) containing locally sourced Steel Slag (SS) and limestone (LS), focusing on stiffness and moisture sensitivity. Four asphalt mixes were tested: Hot mix with limestone (HL), hot mix with steel slag (HS), warm mix with limestone (WL), and warm mix with steel slag (WS). The binder used for all mixes was AC 60/70 penetration grade, and Aspha-min served as the warm mix additive.Testing included Marshall Stability, boiling water, indirect tensile strength, moisture-induced damage (TSR), and dynamic modulus. Image Analysis quantified the aggregate-retained coated area after the boiling test. Despite performance differences, all mixes met Egyptian code requirements for asphalt concrete mixes.Visual inspection and image analysis demonstrated the effectiveness of using steel slag to mitigate asphalt mix stripping. The retained coated area for limestone mixes ranged from 60 % to 75 %, while SS mixes exhibited over 95 %. Dynamic modulus tests indicated no significant stiffness difference with SS, and stability increased by 8 % and 14 % with and without the warm additive. Economic study confirmed the feasibility of utilizing SS. In conclusion, combining Aspha-Min and steel slag improves AC mix production and construction processes, offering a sustainable and advantageous option in Egypt.

Multiscale enhancement mechanism of low-temperature performance for degraded recycled waste rubber asphalt binders: MD simulation and microscopic investigation

Desulfurization and degradation are important processes to facilitate the storage of waste rubber asphalt and improve its utilization. However, this process is extremely complex and the mechanisms underlying the resulting performance enhancement remain unclear. This study aims to investigate the multiscale mechanism of rubber degradation and its impact on the low-temperature performance of degraded rubber modified asphalt (DRMA) binder through differential scanning calorimetry (DSC), bending beam rheometer (BBR), fluorescence microscopy (FM) and Fourier transform infrared spectroscopy (FTIR) tests and molecular dynamics (MD) simulations. The results showed that as the degradation of rubber powder deepens, lightweight components decomposed from the rubber are more easily dissolved into the virgin asphalt, thus improving its dispersion. In addition, the small molecular structure after rubber degradation penetrates and fills the aggregation space between asphalt molecules, effectively increasing the molecular activity of asphalt, thus enhancing the low-temperature performance of asphalt.

Study on the high-temperature performance and self-healing capability of asphalt modified with pyrolysis oil from waste tires and polyphosphoric acid

To develop a novel self-healing asphalt binder and address the challenge of poor performance of waste tire pyrolysis oil-modified asphalt at high temperatures, this study employed polyphosphoric acid and waste tire pyrolysis oil for composite modification of asphalt. Subsequently, comprehensive evaluations of the modified asphalt were conducted using experimental techniques such as temperature sweep, time sweep, differential scanning calorimetry, Fourier-transform infrared spectroscopy, and fluorescence microscopy. The entropy weight method was utilized to determine the optimal dosage of modifiers in the asphalt binder and evaluate the comprehensive performance of the modified asphalt. Experimental results indicate that the introduction of polyphosphoric acid not only effectively maintains the self-healing properties of the modified asphalt but also significantly improves the negative impact of waste tire pyrolysis oil on the high-temperature performance of the asphalt binder. Analysis using the entropy weight method revealed that the optimal dosages of 2% polyphosphoric acid and 4% waste tire pyrolysis oil served as modifiers, resulting in the superior overall performance of the modified asphalt at these concentrations. In conclusion, the development of polyphosphoric acid/waste tire pyrolysis oil composite modifiers offer a novel avenue for the sustainable enhancement of asphalt modification.

Recycling the electric arc furnace waste after geopolymerization in bitumen: experimental analyses and LCA study

The conversion of solid waste materials into cleaner products for road paving. applications appears to be a promising and sustainable option. However, there is still a lack of attention given to quantifying the potential environmental benefits of recycling solid wastes in asphalt pavements, regarding the impact on asphalt performance. To address this gap, the present study investigates the effects of recycling electric arc waste based geopolymers on asphalt binder and mixture characteristics, as well as environmental outputs. For this purpose, geopolymers were incorporated into both neat and SBS-modified binders. A comprehensive rheological investigation was conducted using cutting-edge multiple stress creep recovery (MSCR) and linear amplitude sweep (LAS) analyses. Stability, Marshall quotient, and flow values, as well as dry and wetconditioned tensile strength were considered, to determine asphalt mixture properties. In the Life Cycle Assessment (LCA), greenhouse gases resulting from fuel and energy consumption in each inventory phase were determined. The varying service lifetimes, maintenance and rehabilitation plans, and production and construction requirements of the different asphalt schemes were taken into account. Subsequently, the environmental impacts of the asphalt mixtures, including global warming potential, acidification, eutrophication, and smog formation potential, along with the total energy demand, were calculated across different stages of the LCA. The results show that the geopolymerization process results in important contributions in terms of both environmental savings and pavement performance.

Optimizing the performance of TPCB/SCA composite-modified asphalt using improved response surface methodology

Abstract A composite-modified asphalt was developed by incorporating tire pyrolytic carbon black (TPCB) with a silane coupling agent (SCA) to enhance its ductility and storage stability. The functional binding between asphalt and TPCB was improved by the addition of SCA. The gray correlation comprehensive evaluation method is incorporated into the response surface methodology (RSM), leading to an improved RSM. The improved RSM was employed to optimize the content of the modifier and the preparation process to enhance overall performance. A central composite design-based experiment was conducted to optimize the penetration, softening point, 10°C ductility, Brookfield rotational viscosity, and storage stability indicators of modified asphalt. The response surface of the gray comprehensive evaluation value of the evaluation indicators was calculated using the gray correlation analysis method, and a second-order regression model was established between independent variables such as TPCB, SCA content, and shear time factor and the gray comprehensive evaluation value. This model analyzed the impact of a single variable and variable interaction on the performance of the TPCB/SCA composite-modified asphalt. The optimized model results showed that the preparation parameters that optimize the expected comprehensive performance of the composite-modified asphalt are 9.2% TPCB content, 2.1% SCA content, and a shear time of 56.3 min. Finally, the TPCB/SCA composite-modified asphalt prepared with the improved RSM exhibited the highest gray comprehensive evaluation value and the best overall performance, indicating the feasibility of the optimized preparation parameters with the improved RSM.

Application of fume silica nanoparticles to improve high-temperature rheological performance of terminal blend rubberized asphalt

This study aims to evaluate the impact of fume silica nanoparticles (FSNPs) on the high-temperature rheological properties of terminal blend rubberized asphalt (TBRA). In this study, FSNPs were utilized to modify TBRA asphalt with three different CR contents (30%, 40%, 50%). The micro-morphology of FSNPs was observed through Scanning Electron Microscopy (SEM) experiments. The effects of FSNPs on the high-temperature rheological properties of TBRA were assessed using temperature sweep tests, Multiple Stress Creep Recovery (MSCR), and rotational viscosity tests. Furthermore, the influence of FSNPs on the chemical and thermal properties of TBRA was analyzed through Fourier Transform Infrared Spectroscopy (FTIR) and Thermogravimetric Analysis (TGA) tests. Rheological tests and SEM results indicate that FSNPs can effectively enhance the high-temperature elasticity, fatigue resistance, and deformation resistance of TBRA binders. This improvement is attributed to the unique branched network structure of FSNPs, which plays a pivotal role in enhancing the elasticity within the TBRA asphalt matrix. Additionally, the degradation of TBRA's low-temperature performance due to FSNPs is minimal. Considering the optimal viscosity for FSPN-modified TBRA, recommended ratios are: TB30/6%, TB40/4%, and TB50/2%. FTIR and TGA results demonstrate that the modification of TBRA by FSNPs is primarily physical blending, and the addition of FSNPs enhances the thermal stability of TBRA.

Investigation of the effect of sediment clogging on the hydraulic conductivity of porous asphalt mixes using CFD and DEM methods

This study investigated the impact of sediment clogging on the hydraulic performance of porous asphalt (PA) pavements using a novel numerical approach combining the discrete element method (DEM) and computational fluid dynamics (CFD). In particular, image analysis techniques captured the morphology of real aggregates for the 3D appearance information. Then, the information was used to reproduce aggregates and their gradation in asphalt mixes using DEM, including sediments causing clogging of the PA. The samples in the DEM were transferred to CFD for hydraulic performance simulation. DEM samples were prepared with air voids content of 20% and 25%. Clogging particles with different sizes of 0.5 mm and 0.75 mm were used. The study found that clogging particles can move to deeper layers of the PA pavement but have a high potential to be trapped in upper layers and cause clogging issues in the top 5 mm and middle-to-bottom sections. Due to surface clogging, the air voids content for the 20% porosity PA sample was reduced by approximately 2% on average, whereas up to 7% reduction in air voids content was observed for the 25% PA sample. This led to 37.35% and 42.7% reduction in hydraulic permeability, respectively. The reduction in air voids content below 10 mm from the surface is negligible (0.3–0.7% reduction). Due to the clogging development inside the pore structure, the surface runoff on the top of the sample increases by 8.1% for the 20% air voids asphalt sample case and 37.5% for the 25% voids sample.

Investigation of Surface Modification of Bagasse Fibers: Performance of Asphalt Binders/Mixtures with Bagasse Fibers

The influence of surface modification on the properties of bagasse fibers and asphalt binders/mixtures was investigated. Bagasse fibers were modified by single, binary, and ternary methods with hydrochloric acid, sodium hydroxide, and sodium chlorite, respectively. The physical and chemical properties of bagasse fibers were analyzed by scanning electron microscopy, Fourier transform infrared spectroscopy, and an adsorption test, respectively. The rheological properties of asphalt binders with bagasse fibers or lignin fibers were analyzed by the dynamic shear rheometer test and bending beam rheometer test. In addition, the performance of asphalt mixtures with bagasse fibers or lignin fibers were evaluated by a wheel rutting test, bending test at a low temperature, and water stability test, respectively. In conclusion, the hydrophilic functional groups on the fiber surface were partially eliminated by modification, facilitating the degradation of different fiber components. Furthermore, the degree of fibrillation was improved, and more interfaces with asphalt components were formed, thus enhancing the high-temperature deformation resistance of asphalt binders, but slightly impairing its low-temperature performance. Among all modification methods, the ternary composite modification exerted important influences on fiber structure, oil absorption, and rheological properties of asphalt binders, significantly enhancing the performance of asphalt mixtures. Combined with surface modification methods, bagasse fibers would be promising reinforced pavement materials.

Emission reduction effect of eco-friendly asphalt modified with isocyanate-nanoclay composites

The environmental and health issues associated with the generation of fumes during hot mix asphalt used in road construction necessitate the exploration of cleaner production methods. This study investigated the viability of utilizing isocyanate-nanoclay composites as modifiers for eco-friendly modified asphalt. The composite modified asphalt samples were prepared by adding isocyanate (isophorone diisocyanate, IPDI) and nanoclay (organic montmorillonite, OMMT or attapulgite, ATT) to the base asphalt at varying contents. A device for generating and collecting asphalt fumes was developed. The impact of modifier dosage on fume emission reduction was assessed quantitatively and qualitatively using ultraviolet–visible spectrophotometry and gas chromatography-mass spectrometry, yielding the optimal ratio of composite modifiers. The fume emission reduction mechanism of the modifiers was elucidated by analyzing changes in distribution, functional group composition and micromolecular spacing of asphalt using fluorescence microscopy, fourier-transform infrared reflection, and X-ray diffraction. Results revealed that the intercalation effect between nanoclay and asphalt, combined with chemical reactions between isocyanates and functional groups of nanoclay/asphalt components, effectively impeded the escape of fume molecules. Modified asphalt with 3% ATT+3% IPDI achieved an impressive fume emission reduction rate of 44.67% and enhanced basic performance of base asphalt. The findings contribute to the development of cleaner production methods for hot mix asphalt, thus paving the way for sustainable and safer construction practices in the future.

Secondary degradation of bio-oil degraded crumb rubber and preparation of stable degraded crumb rubber modified asphalt

Using bio-oil to desulfurize and degrade crumb rubber (CR) significantly enhances the compatibility between CR and asphalt, improving the workability of CR-modified asphalt and providing environmental and economic benefits. However, the secondary degradation of bio-oil degraded crumb rubber (ODR) in asphalt hinders the stability of ODR-modified asphalt. To optimize the mechanical performance of ODR-modified asphalt, the secondary degradation behaviors of ODR were investigated. The degree of CR degradation was determined by solubility testing, while the rheological properties and chemical structures of ODR-modified asphalt were characterized through rotational viscometer, dynamic shear rheometer, bending beam rheometer, and Fourier transform infrared spectrometer. The processes for preparing stable ODR modifier and ODR-modified asphalt were proposed to mitigate the damage caused by bio-oil and degraded CR to the high temperature mechanical properties of asphalt. The results show that at lower processing temperatures for ODR-modified asphalt, the volatilization of light components is predominant, while higher processing temperatures prompt secondary degradation of ODR. By stirring at 280°C for 2 hours to acquire moderately degraded CR, and then concentrating it at 220°C for 2 hours, a stable ODR less susceptible to secondary degradation can be obtained. The workability, temperature sensitivity, and low temperature cracking resistance of stable ODR-modified asphalt improve significantly. The reduction of ester group and increase in aromaticity restore the high temperature deformation resistance of ODR-modified asphalt. Further, the inclusion of composite SBS extends the range of rheological properties in ODR-modified asphalt, bolstering the application potential of ODR in asphalt pavement.

Design of SBS molecular structure and contribution mechanism from its soft and hard segments to modify asphalt

ABSTRACT The excellent performance of SBS-modified asphalt is attributed to the release of the SBS soft segment (PB segment) and hard segment (PS segment) in the asphalt. The release mechanism of the SBS soft and hard segments was studied using MD simulation and laboratory experiments, and the optimal molecular structure of SBS for asphalt modification was determined. MD simulation results revealed that SBS with a higher PS content exhibited better compatibility with asphalt. The larger and stronger molecular aggregates of the PS segment improved the high-temperature shear resistance of the asphalt but reduced the molecular mobility of the system. Additionally, radial distribution function analysis showed varying degrees of aggregation behaviour of asphaltenes with different segment ratios of polymer modifiers. Laboratory experiments were conducted using synthetically prepared SBS modifiers with specific segment ratios, as well as PB and PS monomer modifiers. Conventional tests and rheological experiments indicated that the PB segment improved the low-temperature performance of the asphalt, while the PS segment enhanced its high-temperature performance. The experimental results of the Cole–Cole plots are consistent with the solubility parameter results. Morphological studies revealed a two-phase continuous structure formed between SBS and asphalt when the SBS segment ratio was approximately 30/70.