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In this study, the feasibility of using bamboo bark fibers as modifiers to enhance asphalt mortar performance was investigated. Bamboo bark fibers were modified with NaOH, KH570 silane coupling agent, and nano-SiO2, and their preparation methods were established. The modified fibers were assessed for their oil absorption, thermal stability, and hydrophobicity. The asphalt mortar was evaluated for three key indicators: rutting resistance, deformation resistance, and durability at high temperatures. The microscopic morphology and modification mechanisms of the fibers were also studied. The results showed that modification with NaOH increased fiber porosity and surface roughness, while KH570 and its hydrolysis products enabled nano-SiO2 grafting onto the fibers, improving their adsorption to asphalt. The NaOH-KH570-nano-SiO2 ternary-composite-modified bamboo bark fiber (NKSBF) demonstrated superior hydrophobicity, oil absorption, and thermal stability at the asphalt mixing temperature. Among the modified fibers, asphalt mortar containing 3% NKSBF showed the best performance based on three key indicators, increased the shear strength by 96.4% and the softening point by 7.1% compared to the base asphalt, and increased the ductility by 1% compared to lignin fiber asphalt mortar. The incorporation of 3% bamboo bark fibers improved the rutting resistance, deformation resistance, and durability of short-term-aged asphalt mortar, with NKSBF showing the most significant improvement. [ABSTRACT FROM AUTHOR]

Polymers, rubber, carbon black, nanomaterials, and other substances are frequently used for producing modified asphalt binders, which strengthen their ability to withstand fluctuating temperatures and growing vehicular loads. In order to achieve the intended performance, crosslinking agents/additives are frequently utilized to enhance the compatibility of various modifiers with the asphalt binder. This literature review paper provides a discussion on the use of different crosslinking agents, such as sulfur, dithiodimorpholine (DTDM), tetraethyl thiuram disulfide (TETDS), polyphosphoric acid (PPA), trans-polyoctenamer rubber (TOR), and peroxide, in the formulation of modified asphalt binder with different polymers, such as styrene-butadiene-styrene (SBS), ethylene vinyl acetate (EVA), and polyethylene (PE), as well as different rubber modifiers, such as styrene-butadiene rubber (SBR), crumb rubber (CR), and ethylene-propylene-diene-monomer (EPDM) rubber. The fundamental concepts of the chemistry of modified asphalt binder are covered first, and then various crosslinking additives/agents and their effects on the storage stability/compatibility and chemical and rheological properties of modified asphalt binder are reviewed. The environmental effects of using these crosslinking agents with modified asphalt binders are also covered in the present work. The paper concludes with recommendations for future research studies using crosslinking agents with different types of modified asphalt binders. [ABSTRACT FROM AUTHOR]

Liquid rubber (LR) has been proven to be a valuable asphalt modifier capable of addressing the existing deficiencies associated with crumb rubber–modified asphalt (CRMA), including poor workability and storage stability. Therefore, an accessible preparation method based on olefin metathesis was explored to produce optimal LR from crumb rubber (CR) in the laboratory. This research established the optimal laboratory preparation conditions for LR and investigated the performance of liquid rubber–modified asphalt (LRMA) mixture when used in pavement. A total of 32 LR samples were generated by olefin metathesis and physical swelling under various catalytic and swelling conditions. The physical properties, viscosity, and storage ability of LRMA were evaluated to select the optimal preparation parameters for LR. A comprehensive analysis was performed to compare the physicochemical characteristics of LR and the original CR through microscopic examinations with scanning electron microscopy (SEM), Fourier-transform infrared spectrometry (FTIR), and gel permeation chromatography (GPC). An in-depth evaluation assessed the stability at high temperatures, the properties at low temperatures, and the moisture stability of LRMA and CRMA mixtures. Experimental results showed that the optimal laboratory preparation conditions for LR were a catalyst dosage between 3‰ and 5‰, a catalytic duration of 48 h, a swelling temperature of 160°C, and a swelling time of 8 h. Moreover, LR possessed a smooth surface without rubber particles. The molecular weight and distribution of LR were considerably reduced compared with those of CR after olefin metathesis and physical swelling. The introduction of LR significantly enhanced the cracking resistance of the base asphalt mixture. However, the enhancement effect of LR on the base asphalt mixture to resist high-temperature rutting and moisture damage was inferior to that of CR. [ABSTRACT FROM AUTHOR]

Selection of a proper binder–aggregate combination is an important step to ensure optimum resistance to moisture-induced damage in asphalt mixes. In recent years, such selection has become more crucial as asphalt industries are using various additives and modifiers in asphalt mixes that can substantially change bonding strength of a binder–aggregate system. Also, environmental factors such as oxidative aging can affect the chemical compositions of the binder and influence moisture-induced damage resistance of a mix. In order to understand the mechanisms of moisture-induced damage, it is important to determine the chemical and thermodynamic properties of constituent materials of a mix and identify their contributions to the bond strength. The present study was undertaken to explore the effects of aggregate types, additives, and aging on the moisture susceptibility of asphalt mixes using chemical and thermodynamic approaches. For this purpose, a PG 64-22 and a PG 76-28 binder were blended with a warm mix asphalt (WMA) additive, an antistripping agent (ASA), a reclaimed asphalt pavement (RAP) binder and polyphosphoric acid (PPA). The surface free energy (SFE) components of these binder blends under unaged, short-term aged, and long-term aged conditions were determined using the dynamic Wilhelmy plate (DWP) method for measuring dynamic contact angle. Chemical analyses of the binder blends were carried out using x-ray fluorescence (XRF) analysis and Fourier transform infrared (FTIR) spectroscopy. Properties of five commonly available local aggregates were determined using XRF and universal sorption device (USD) testing. The SFE components of the binders and aggregates were used to quantify bonding characteristics of binder–aggregate systems under dry and wet conditions. Aggregate properties significantly influenced the moisture-induced damage potential of a mix. In addition, an increase in carbonyl and sulfoxide functional groups resulted in increased moisture susceptibility with aging. Therefore, the presence of amine functional groups in both WMA and ASA is expected to provide resistance to moisture-induced damage and conversely the presence of PPA may reduce resistance to moisture-induced damage of a binder–aggregate system. [ABSTRACT FROM AUTHOR]

The application of nanomaterials as modifiers in the field of asphalt is increasingly widespread, and this paper aims to systematically review research on the impact of nanomaterials on asphalt viscosity. The results find that nanomaterials tend to increase asphalt's viscosity, enhancing its resistance to high-temperature rutting and low-temperature cracking. Zero-dimension nanomaterials firmly adhere to the asphalt surface, augmenting non-bonding interactions through van der Waals forces and engaging in chemical reactions to form a spatial network structure. One-dimensional nanomaterials interact with non-polar asphalt molecules, forming bonds between tube walls, thereby enhancing adhesion, stability, and resistance to cyclic loading. Meanwhile, these bundled materials act as reinforcement to transmit stress, preventing or delaying crack propagation. Two-dimensional nanomaterials, such as graphene and graphene oxide, participate in chemical interactions, forming hydrogen bonds and aromatic deposits with asphalt molecules, affecting asphalt's surface roughness and aggregate movement, which exhibit strong adsorption capacity and increase the viscosity of asphalt. Polymers reduce thermal movement and compact asphalt structures, absorbing light components and promoting the formation of a cross-linked network, thus enhancing high-temperature deformation resistance. However, challenges such as poor compatibility and dispersion, high production costs, and environmental and health concerns currently hinder the widespread application of nanomaterial-modified asphalt. Consequently, addressing these issues through comprehensive economic and ecological evaluations is crucial before large-scale practical implementation. [ABSTRACT FROM AUTHOR]

Direct-injection SBS modified asphalt has advantages such as easy quality control, low cost, and minimal pollution. It can address the issue of unstable quality in conventional wet-process SBS modified asphalt and has been gradually widely applied in recent years. This study investigated the aging resistance performance of direct-injection SBS modified asphalt at different dosages through short-term aging. By conducting temperature scanning tests, mid-temperature fatigue performance tests, low-temperature rheological property tests, and atomic force microscope tests on the aged direct-injection modified asphalt, the aging resistance performance of the SBS modified asphalt was studied from macroscopic to microscopic scales. The macroscopic experimental results indicated that the direct-injection SBS modified asphalt exhibited an increase in elastic components and fatigue life after short-term aging. During the aging process, the Guolu direct-injection SBS modified asphalt showed a secondary development phenomenon. The microscopic test results revealed that, after short-term aging, both conventional wet-process SBS modified asphalt and Liaohe direct-injection SBS modified asphalt exhibited reduced roughness due to changes in the content of the four components and the degradation of SBS. In contrast, the Guolu direct-injection SBS modified asphalt exhibited increased surface roughness due to further swelling development, consistent with the conclusions drawn from the macroscopic tests. [ABSTRACT FROM AUTHOR]

In this study, the effect of biochar from oat hulls (BO) on the rheological properties of a PG 64-22 asphalt binder was evaluated using a full factorial design, which included the following factors: pyrolysis temperature (PT) (300 °C and 500 °C), BO particle size (<20 µm and <75 µm), and the amount of BO (2.5%, 5%, and 7.5%). First, the morphological and physicochemical properties of BO were analyzed by comparing it with graphite powder (CFG) and commercial activated carbon (CAC). The physicochemical properties of the modified asphalt binder were then evaluated using confocal laser microscopy, scanning electron microscopy (SEM–EDX), and Fourier-transform infrared spectroscopy (FTIR). Its storage stability was also evaluated. Subsequently, the rutting parameter G*/sin(δ) and the Fraass breaking point were analyzed to select asphalt binders that extended their viscoelastic range. The asphalt binders selected were those with 2.5%, 5%, and 7.5% BO, produced at a PT of 300 °C with a particle size <20 µm (BO300S). Next, the rheological properties of the selected samples were evaluated by testing for rotational viscosity, rutting parameter G*/sin(δ), multiple stress creep recovery (MSCR), fatigue parameter G*·sin(δ), and creep stiffness by bending beam rheometry (BBR). The rheological aging index according to rutting parameter G*/sin(δ) (RAI) was also evaluated. These tests were conducted in different states of the asphalt binder: original, short-term aged, and long-term aged. According to the results, the application of BO300S significantly increased the resistance of the asphalt binder to rutting and rotational viscosity, proportional to the amount added to the asphalt binder. Moreover, low modifier percentages improved fatigue resistance, outperforming CFG and CAC. In addition, it performs well at low service temperatures, registering better resistance than the control asphalt binders. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Previous studies indicate that traditional asphalt mixtures lack the ability to withstand the stresses caused by heavy traffic volumes under high temperatures. To enhance the rutting resistance of flexible pavement under high levels of temperature and loading, extensive laboratory experiments were carried out. A 60/70 grade bitumen was used as a neat sample for comparison. The study introduced three distinct polymers, polypropylene (PP), low-density polyethylene (LDPE), and acrylonitrile butadiene styrene (ABS), at varying concentrations by weight into the neat bitumen. Initially, conventional tests were performed to evaluate the conventional properties of both the neat and modified bitumen, while aggregate tests assessed the mechanical properties of the aggregates. Subsequently, a Marshall mix design was performed to determine the optimum bitumen content (OBC) in the asphalt mixture. Finally, wheel-tracking tests were performed under a specific load and temperature to investigate the rutting behavior of the modified asphalt mixtures. The results of this comprehensive study revealed that the modified asphalt mixtures displayed improved resistance to rutting compared to the neat asphalt mixture. Furthermore, it was also observed that the LDPE exhibited a superior performance against rutting, followed by the PP and ABS. At polymer contents of 3%, 5%, and 7%, the LDPE achieved reductions in rut depth of 13%, 24%, and 33%, respectively, outperforming both PP- and ABS-modified asphalt. These findings not only enhance our understanding of asphalt behavior under diverse conditions but also highlight the potential of plastic-modified asphalt as an effective solution for mitigating rutting problems in road pavements. By incorporating plastic modifiers into asphalt mixtures, this approach aligns with the principles of sustainable construction by reducing plastic waste while improving pavement durability and performance. [ABSTRACT FROM AUTHOR]

Predicting pavement surface friction during the design stage allows engineers to optimize the design of the roadway to provide the appropriate level of friction for the intended use of the road in a safe and cost-effective manner. The main goal of the study is to propose a methodology to predict pavement surface friction during the design stage. Thus, this study analyzes the role of aggregate Fineness Modulus (FM) and Hot Mix Asphalt (HMA) volumetrics including Air Voids Volume (Va) and Effective Binder Volume (Vbe) on fabricating the surface texture. Surface frictional properties were evaluated using the British Pendulum Test (BPT) and the Sand Patch Test (SPT). The data were analyzed using the analysis of variance (ANOVA) test. Several statistical modeling techniques including Multiple Linear (ML) regression, Non-Linear Stepwise (NLSW) regression with all possible interactions, Non-Linear Beta (NLB) regression, Non-Linear Curve Fitting (NLCF) regression, and multilayer neural network (MNN) were utilized. Models were evaluated using synthetical data and compared using Post-Hoc analysis. The study evaluated nine types of mixes including different gradations with different Nominal Maximum Aggregate Sizes (NMAS) and several asphalt modifiers. The results revealed that Mean Textures Depth (MTD) and British pendulum Number (BPN) values are primarily influenced by FM, followed by Va and Vbe, respectively. According to ANOVA results, the two-level interaction showed that only when FM interacts with either Va or Vbe, the interaction is significant for both MTD and BPN. MNN models had the highest Coefficient of Determination (R2) values for both MTD and BPN. However, the sensitivity analysis and the Post-Hoc analysis revealed that due to the low number of data used to generate the models, statistical regression methods had comparable results and resulted in more accurate prediction than MNN. The NLCF was found to be the most reliable model for predicting both BPN and MTD. [ABSTRACT FROM AUTHOR]

Major global consumption of coffee has led to the generation of a substantial amount of spent coffee grounds (SCG), which contribute to environmental burdens. Research on using SCG for asphalt modification is limited. This study aimed to investigate the effectiveness of using biochar from spent coffee grounds (SBC) produced through low-oxygen pyrolysis as a modifier for asphalt, to enhance high-temperature performance and aging resistance. The results demonstrated excellent compatibility between SBC and asphalt binder without causing agglomeration. The introduction of SBC significantly enhanced asphalt's high-temperature stability and resistance to deformation, while some adverse effects on low-temperature performance were found. The inclusion of SBC improved the anti-aging properties of asphalt, as indicated by various aging performance indices. A decreasing trend was observed for sulfoxide (S═O) 1,030 cm−1. Atomic force microscopy (AFM) images revealed the changes in the size and shape of beelike structures, with smaller bee structures observed in SBC-modified asphalt (SBCMA). Overall, these microscopic structures were consistent with the rheological properties. Due to the improvement of high-temperature stability and anti-aging properties, SBC could prove to be an environmentally friendly and sustainable modifier for asphalt. [ABSTRACT FROM AUTHOR]

Carbon nanotube (CNT) is a material with high modulus, high tensile strength, good flexibility and large specific surface area. This material has become very popular and has been also applied as an asphalt modifier. In the current research, multi-walled carbon nanotubes (MWCNTs) and styrene-butadiene-styrene (SBS) were employed as modifiers to fabricate MWCNTs/SBS composite-modified asphalt binder (hereinafter referred to as MCSA). The technical performance of MCSA was evaluated by performance tests and the optimal content of MWCNTs was determined. MCSA dispersion characteristics and interactions of components were investigated by microscopic test methods. Interactions of molecules and tensile behavior of MWCNTs in MCSA were explored by molecular dynamics (MD) simulation. The modification mechanism of MWCNTs was studied at the macro, micro and molecular levels. The following conclusions were drawn: According to macroscopic test results, the optimal content range of MWCNTs was 0.4% to 0.6%. MWCNTs modification process on asphalt binder was a physical modification. MWCNTs enhanced interactions among components and this effect was most obvious when MWCNTs content was 0.6%. The results of the macroscopic test were verified by the microscopic test. MWCNTs molecules could couple with SBS modifier as well as asphalt component molecules, thereby enhancing the interaction of each component in the system. MWCNTs mainly enhanced molecular interactions by increasing van der Waals energy in MCSA system, to make it more stable. MWCNTs do not break during the pull-out process. The molecules of asphalt component, SBS modifier and MWCNTs penetrated each other, which enhanced system stability to resist external loads and improved the mechanical properties of MCSA. [ABSTRACT FROM AUTHOR]

A recently used material that shows environmental and technical advantages for use as an asphalt binder modifier is biochar (BC). Different biomasses can be converted into BC by pyrolysis. One agro-industrial biomass that is abundant in copious quantities is oil palm mesocarp fiber (OPMF) obtained from African palm cultivation. In the present study, the use of a BC obtained from OPMF (BC-OPMF) as a modifier of asphalt binder (AC type) to produce a hot mix asphalt (HMA) was evaluated. This type of BC has not been investigated or reported in the reference literature as a binder and/or asphalt mix modifier. Initially, AC was modified with BC in three ratios (BC/AC = 5, 10, and 15%, with respect to mass) to perform penetration, softening point, and rotational viscosity tests; rheological characterization at high and intermediate temperatures; and scanning electron microscope (SEM) visualization. Based on this experimental phase, BC/AC = 10% was chosen to manufacture the modified HMA. Resistance parameters under monotonic loading (stability—S, flow—F, S/F ratio of the Marshall test, and indirect tensile strength in dry—ITSD and wet—ITSC conditions) and cyclic loading (resilient modulus, permanent deformation, and fatigue resistance under stress-controlled conditions) were evaluated on the control HMA (AC unmodified) and the modified HMA. Additionally, the tensile strength ratio (TSR) was calculated to evaluate the resistance to moisture damage. Abrasion and raveling resistance were evaluated by performing Cantabro tests. BC-OPMF is shown to be a sustainable and promising material for modifying asphalt binders for those seeking to increase stiffness and rutting resistance in high-temperature climates, resistance to moisture damage, raveling, and fatigue without increasing the optimum asphalt binder content (OAC), changing the volumetric composition of the HMA or increasing the manufacturing and construction temperatures. [ABSTRACT FROM AUTHOR]

Diverse types of waste are generated during the sawmilling process. One of them is pine wood shavings (PWSs). This waste can be transformed by pyrolysis into biochar (BC) to produce a sustainable material that can serve as an asphalt binder modifier. In this study, a BC produced with PWS as biomass (BC-PWS) was used to modify the properties of an asphalt cement (AC). This type of BC has not been investigated as a modifier of ACs and asphalt mixtures. Three BC-PWS contents were used for this purpose (BC/AC = 5, 10, and 15% by weight). Conventional characterization tests such as penetration, softening point, and rotational viscosity were performed on the unmodified and modified ACs. Rheological properties were also evaluated at high and intermediate temperatures, and observations were made with a scanning electron microscope (SEM). The modified BC/AC = 10% binder was chosen to manufacture a hot-mix asphalt (HMA). Marshall, indirect tensile strength—ITS, Cantabro, resilient modulus (RM), permanent deformation, and fatigue resistance (under stress-controlled mode) tests were performed on the HMA. The Tensile Strength Ratio (TSR) parameter was determined from ITS tests. BC-PWS is a promising material as an AC modifier from the technical-environmental point of view, which tends to enhance the evaluated properties of AC and HMA (monotonic load, rutting, fatigue, moisture damage, and raveling resistance), without resorting to increases in asphalt content or increases in mixing and compaction temperatures. [ABSTRACT FROM AUTHOR]

In low-temperature environments, asphalt materials harden easily and become brittle, and the repeated action of traffic load further aggravates the cracking of and damage to the asphalt mixture. In order to explore high-performance asphalt pavement materials that are more suitable for cold climates, this paper selected four modifiers, namely SBS, rubber powder, SBR and TPS. With SBS as the main agent, combined with other modifiers, three types of base asphalts with grades of 70#, 90# and 110# were compositely modified to prepare 12 different combinations of composite-modified asphalt samples. The optimal dosage of the modifier was determined by the basic performance test of asphalt, and the compatibility, interaction energy and mechanical properties of the modifier and base asphalt at different temperatures were analyzed by molecular dynamics simulation. Subsequently, the high- and low-temperature rheological properties of various modified asphalts were systematically evaluated using a dynamic shear rheology test (DSR) and a bending beam rheology test (BBR), and the rheological properties and road performance indicators of each composite-modified asphalt were comprehensively compared so as to select the road materials most suitable for cold areas. The research results show that different grades of base asphalt and modifiers show good compatibility in the range of 160–175 °C. Among them, rubber powder and TPS modifier significantly improve the high-temperature mechanical properties of SBS-modified asphalt, while rubber powder and SBR modifier significantly improve its low-temperature mechanical properties. The DSR and BBR test results further show that SBS/rubber powder composite-modified asphalt exhibits excellent rheological properties under both high- and low-temperature conditions, and is the preferred solution for road materials in cold regions. [ABSTRACT FROM AUTHOR]

Though warm mix asphalt (WMA) technology has been introduced for a long time, there is still reluctance in the industry to utilize it in practice. In regions like India, where WMA incorporation into road construction has been limited over the past two decades, building confidence in local binders is imperative for widespread adoption. Thus, the present study appraises the effect of three commonly used WMA additives in India, namely Sasobit®, Evotherm®, and Zycotherm®, with base binder VG-30 on the rheological and mixture performance parameters. Three dosages of each WMA additive were blended with the control binder to give ten binder combinations. Different binder evaluations such as Superpave grading and parameters, frequency sweep testing, multiple stress creep recovery test, and linear amplitude sweep test were conducted for comparative dynamic mechanical analysis. Based on the binder testing results, suitable dosages of WMA additives were established, and mixture testing was carried out using these specific additive dosages. Binder evaluations showed improvement in high-temperature characteristics with Sasobit® and better fatigue performance with Evotherm®, while Zycotherm® did not alter binder properties significantly. The asphalt mixture testing results indicated satisfactory performance with the three additives based on Marshall stability and flow testing. The WMA additives also showed enhancement in moisture susceptibility based on the modified Lottman test with Zycotherm® demonstrating the best performance. Overall, the study underscores promising effects of the three WMA additives across different parameters, signaling their potential for widespread application in real-world scenarios. [ABSTRACT FROM AUTHOR]

Asphalt binder is the most common material used in road construction. However, the need for more durable and safer pavements requires a better understanding of asphalt's aging mechanisms and how its characteristics can be improved. The current challenge for the road industry is to use renewable materials (i.e., biomaterials not subjected to depletion) as a partial replacement for petroleum-based asphalt, which leads to reducing the carbon footprint. The most promising is to utilize biomaterials following the principles of sustainability in the modification of the asphalt binder. However, to understand whether the application of renewable materials represents a reliable and viable solution or just a research idea, this review covers various techniques for extracting bio-oil and preparing bio-modified asphalt binders, technical aspects including physical properties of different bio-oils, the impact of bio-oil addition on asphalt binder performance, and the compatibility of bio-oils with conventional binders. Key findings indicate that bio-oil can enhance modified asphalt binders' low-temperature performance and aging resistance. However, the effect on high-temperature performance varies based on the bio-oil source and preparation method. The paper concludes that while bio-oils show promise as renewable modifiers for asphalt binders, further research is needed to optimize their use and fully understand their long-term performance implications. [ABSTRACT FROM AUTHOR]

To address the issue of insufficient durability of traditional modified emulsified asphalt in the application of cold mix and cold paving anti-skid wear layers, this study utilizes cationic waterborne polyurethane (PU+) for composite modification to enhance adhesion and performance across a range of temperatures. Initially, composite-modified emulsified asphalt samples were prepared with varying dosages of PU+ according to a gradient method. Routine performance tests were conducted on the evaporated residues for analysis. Advanced rheological tests, including temperature sweep (TS), frequency sweep (FS), linear amplitude sweep (LAS), and multi-stress creep recovery (MSCR) tests, were performed using a dynamic shear rheometer (DSR). Surface free energy (SFE) tests were conducted with a fully automated surface tension meter (STM). A comprehensive evaluation of the high-temperature rheological properties, fatigue properties, adhesion properties, and water damage resistance of the modified emulsified asphalt residues was carried out. Chemical changes before and after modification were characterized using Fourier transform infrared spectroscopy (FTIR), and the distribution of polymers in the evaporated residue was observed using fluorescence microscopy (FM). The results demonstrated that cationic waterborne polyurethane significantly enhanced the fatigue and adhesion properties of SBS-modified emulsified asphalt, but it also weakened the water damage resistance of asphalt. MSCR tests revealed that the addition of cationic waterborne polyurethane might reduce the elastic recovery performance of modified asphalt, thereby weakening its resistance to rutting. Among the samples, the modified asphalt with a PU+ content of 6% exhibited good high-temperature shear resistance and elastic recovery performance, demonstrating the best anti-rutting performance. [ABSTRACT FROM AUTHOR]

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One of the primary causes of premature pavement deterioration in Asphalt Concrete (AC) mixtures is the breaking of the adhesive bond between the aggregate and the binder. The purpose of this study is to assess the performance characteristics of AC mixture utilizing the Rediset LQ-1200 additive. In order to achieve this goal, tests such as the Marshall Stability (MS), Marshall Stability Ratio (MSR), Indirect Tensile (IDT), indirect tensile cracking, and Wheel Tracking (WT) were deployed to evaluate the mechanical properties of AC mixtures. The findings demonstrated a considerable improvement in the physical parameters of the AC mixture with the Rediset LQ-1200 additive compared to the base AC mixture. The MS and MSR were improved by about 28% and 13%, respectively, while the AC mixture's resistance to rutting and cracking was efficiently increased. [ABSTRACT FROM AUTHOR]

Adding graphene microflakes with excellent mechanical properties to asphalt materials can promote the development of sustainable transportation infrastructure. Recently, graphene oxide–modified asphalt has gained popularity due to its enhanced storage stability, ease of construction, and high-temperature stability. However, the modification mechanism of graphene oxide and polymer modifiers within asphalt remains unclear. This study aims to investigate the mechanism of action of aminated graphene oxide and styrene-butadiene-styrene (SBS) within asphalt and elucidate their influence on the properties of composite-modified asphalt. This research utilized X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), dynamic shear rheometer (DSR), multiple stress creep recovery (MSCR), bending beam rheometer (BBR), and thermogravimetry analysis (TGA) to explore the performance of composite-modified asphalt and the modification mechanism of modifiers. X-ray diffraction and Fourier transform infrared spectroscopy showed that the modification effect was better, the surface wrinkles of modified graphene oxide increased, and the interlayer spacing expanded, which was favorable to its compatibility with asphalt. Conventional test and Brookfield viscosity revealed that composite-modified asphalt possessed favorable high-temperature resistance and plasticity compared to the original asphalt. Additionally, dynamic shear rheological and storage stability tests indicated that the addition of aminated graphene oxide not only improved the viscoelastic properties of asphalt but also enhanced the compatibility between various substances. Multiple stress creep recovery and bending beam rheometer tests measurements confirm that the composite-modified asphalt exhibits superior high-temperature rutting resistance and low-temperature crack resistance. Fluorescence microscopy analysis demonstrated the uniform distribution of the modifier and SBS within the asphalt, while thermogravimetry analysis revealed that composite-modified asphalt exhibited higher thermal stability compared to SBS-modified asphalt. This study holds significant importance in advancing the development and practical application of road modification materials. [ABSTRACT FROM AUTHOR]

This paper aims to evaluate the possibility of using recycled concrete aggregate (RCA) as an alternative to coarse natural aggregates (NAs) in warm-mix asphalt (WMA). The index engineering characteristics of the RCA used for the asphalt mixtures were determined. The physical and rheological characteristics of virgin and modified asphalt binders were specified using conventional and performance grade (PG) tests. The WMA was manufactured by two approaches. The first approach involved modifying the asphalt binder properties by incorporating Sasobit as an organic additive into the heated asphalt binder (wet process). The second approach incorporated Asphamin as a synthetic zeolite foaming additive into the aggregate during the mixing process (dry process). Nanosilica fume (NSF) was used as an economical alternative to nanomaterials to improve the investigated WMA's performance compared with a control hot-mix asphalt (HMA) containing 100% coarse RCA/100% fine NA. The performance of the asphalt mixtures in terms of Marshall, indirect tensile strength (ITS), dynamic modulus (E*), and flow number (FN) was also estimated. The Marshall test results of WMA mixtures with the two types of additives were relatively identical with the control HMA mixture with a slight difference in the optimum asphalt content (OAC). However, the NSF incorporation as a replacement to the mineral filler within the WMA mixtures led to an increase in stability values by up to 35%, especially at 40% NSF with low OAC. The tensile strength ratio (TSR) values for WMA mixes were lower than 80%, but the use of NSF showed a slight enhancement in their values to meet the minimum requirement set by Egyptian specifications. Also, the results revealed a decrease in E* and FN values for the WMA mixtures compared with those for the HMA control, whereas the addition of NSF enhanced the results significantly to outperform the HMA. Practical Applications: This research highlights the use of recycled concrete aggregate as a replacement for coarse natural aggregates for manufacturing warm-mix asphalt with two different technologies and compares their performance with hot-mix asphalt. In addition, the effect of using by-product materials such as nanosilica fume as an economical alternative to nanomaterials for raising the efficiency of warm-mix asphalt mixtures was sought. The results provide a better understanding of the performance of warm-mix asphalt mixtures, which contribute effectively to achieving environmental sustainability in the pavement industry. [ABSTRACT FROM AUTHOR]

Graphene and its derivatives have garnered significant attention as novel nanomodifiers in the asphalt industry. Despite its vast potential, poor compatibility and dispersion between graphene and asphalt have been persistent challenges for researchers. To prepare well-dispersed graphene materials, polyvinylpyrrolidone (PVP) was grafted onto water-soluble graphene (WG), resulting in PVP-WG composites. This PVP-WG composite was introduced into matrix asphalt as a modifier to improve the compatibility and dispersion of graphene with asphalt. Various advanced techniques such as Fourier transform infrared spectroscopy, laser particle size analyzer, scanning electron microscopy, and X-ray diffraction confirmed the successful attachment of PVP to the surface of water-soluble graphene, thereby increasing the spacing between WG and promoting the intercalation of asphalt molecules. The loose structure of PVP facilitated the effective binding between WG and asphalt molecules. The multiple stress creep recovery and dynamic shear rheometer tests demonstrated that PVP-WG was effective in enhancing the elastic recovery performance, high temperature resistance to deformation, and viscoelastic properties of the asphalt binder. In addition, the results of the bending beam rheometer test showed that PVP-WG slightly reduces the low-temperature performance of asphalt, but PVP significantly improves the low-temperature cracking resistance of WG-modified asphalt. This study provides valuable insights into the potential application of graphene in asphalt pavement materials. [ABSTRACT FROM AUTHOR]

This article is a continuation of work on the use of plastic waste (such as PP, PS, LDPE, HDPE, and their mixtures) processed in the proprietary pyrolysis process as asphalt additives. The article carried out detailed tests of the mixes of selected additives with pen-graded bitumen 50/70, taking into account, among others, the influence of impurities and the ratio of PE to PP in the additives as well as short- (RTFOT) and long-term (RTFOT + PAV) ageing. An extensive research program was carried out, including functional and rheological tests in a wide range of temperatures. First, tests of stability and adhesion to various types of aggregates were carried out, demonstrating the usefulness of the proposed additives. Then, the elastic recovery and the impact of technological ageing on penetration, Fraass breaking temperature, and plasticity range were assessed. The same binder mixes were subjected to rheological tests in a wide range of technological and operational temperatures, assessing, among others, viscosity, the norm of the complex shear modulus, elastic recovery and compliance in the MSCR test, and stiffness in the bending beam rheometer. This entire class of tests was carried out for clean samples and those containing impurities, indicating their impact on individual material parameters. [ABSTRACT FROM AUTHOR]

Moisture damage in asphalt mixtures is typically attributed to the loss of bond strength at the interface of the asphalt binder and aggregate matrix. Selecting an appropriate combination of materials that resist moisture-induced damage is therefore critical. This concern is of utmost importance when asphalt mixtures are prepared at lower temperatures (i.e. warm-mix asphalt (WMA) mixtures). An attempt was thus made to quantify the impact of moisture on asphalt mixtures prepared using four different WMA additives and two aggregates through bond strength tests. The results showed that WMA binders imparted similar or even higher bond strength than the base asphalt binder, regardless of the aggregate source and moisture exposure (wet or dry). The use of WMA additives improved the moisture sensitivity (evaluated through the bond strength ratio), despite lower production temperatures, compared with the base asphalt binder (VG30). Statistical analysis showed that the asphalt binder type significantly affected the bonding mechanism and moisture sensitivity. Based on the ranking protocol used in this study, use of the chemical-based WMA additive Rediset showed the best performance compared with other WMA additives in VG30. [ABSTRACT FROM AUTHOR]

Solid waste recycling and reuse have attracted great interest as environmentally friendly modifiers for asphalt pavements in recent years, and phosphogypsum whiskers (PSWs) synthesized by phosphogypsum (PSP) wastes were used as the main modifying material to develop an environmentally friendly asphalt binder in this study. PSWs could significantly enhance the deformation resistance and fatigue performance of asphalt binder but were prone to cracking at low temperature. To alleviate this problem, the novel idea of developing a PSW composite modified asphalt binder was proposed in this study. The organic coating method was used to surface modify PSWs by using surfactants and ultrasonic vibrator to enhance the compatibility of PSWs with asphalt binder. Then a composite modifier containing modified PSW (MPSW) was developed by the uniform design method (UDM), and the preparation process of the modifier was investigated by response surface method (RSM) on this basis. The physical performance of modified asphalt binder was investigated by conventional performance tests; the high-temperature performance, rutting resistance, and fatigue performance were investigated by several rheological tests; and the low-temperature performance was evaluated by the force ductility test (FDT). The microstructure and modification mechanism were characterized by the Fourier transform infrared spectroscopy (FTIR) test and differential scanning calorimetry (DSC) test. The results showed that the self-developed modifier (MPGJ-I) could effectively reduce the negative effects of MPSW on conventional physical properties, and it exhibited a significant aging resistance compared with other commonly used modifiers. In addition, the modified asphalt binder showed a significant enhancement in high-temperature performance, rutting resistance, and fatigue performance. The MPGJ-I not only solved the adverse effect of MPSW on low-temperature performance, but also enhanced the low-temperature performance to a certain degree. The MPGJ-I was only physically mixed with asphalt binder and did not change its chemical structure. The MPGJ-I reduced the influence of MPSW on glass transition temperature (Tg) and improved the thermodynamic properties of asphalt binder at low temperatures. The comparison study revealed that the MPGJ-I could comprehensively enhance the service performance of virgin asphalt binder, and the recommended dosage of MPGJ-I was 6%. [ABSTRACT FROM AUTHOR]

Fatigue cracking, a major distress in asphalt pavements, is worsened by traffic and climate conditions such as moisture effects on constituents and interfacial properties. However, investigation on fatigue's evolution in different scales under moisture effect is still scarce in the open literature. This work aims to assess moisture‐induced damage effects on asphaltic materials focusing on the failure of asphalt binders, the aggregate‐binder interface, and mixture. The methodology included tests under dry and wet conditions: linear amplitude sweep (LAS); asphalt bond strength (ABS) in different temperatures and pull rates for interfaces; indirect tensile strength (ITS), and tension‐compression fatigue on asphalt mixtures. Key findings were: (i) moisture damage presents growing effects from binders to mixtures; (ii) LAS test results were not sensitive to moisture; (iii) ABS tests require proper field temperatures for accuracy; (iv) ITS ratio provide reliable conditioned fatigue expectations; and (v) fatigue testing without conditioning to hydrodynamic effects or real moisture susceptibility might overestimate service‐life. Highlights: Moisture damage presents growing effects from binders to mixtures;LAS results were not sensitive to moisture;ABS tests require proper field temperatures for accuracy;ITSR indicates conditioned fatigue behavior, unconditioned tests might overestimate service life. [ABSTRACT FROM AUTHOR]

Concern for the environment has been increasingly evident in recent years, knowing that one of the main environmental problems found in urban centers is associated with the urban heat island phenomenon. In view of this environmental problem, one way to obtain cooler paved surfaces under the incidence of solar radiation is to increase their albedo, through the coloring of paved surfaces. Thus, the objective of this work was to investigate the potential of using waste high-density polyethylene (HDPE) waste to color asphalt mixture and minimize the urban heat island phenomenon due to the high reflection of HDPE colors. The research was structured in three main strands: (i) rheological characterization of the binder modified by HDPE in the contents of 1%, 2%, and 3%; (ii) mechanical analysis of asphalt mixtures with HDPE; (iii) evaluation of the use of HDPE on the asphalt surface and its contribution to the reduction of surface temperature. A statistical Student's t test verified the significance of the mechanical performance data of the mixtures. The results showed that the addition of 2% of HDPE contributed to the asphalt binder presenting rheological benefits at high temperatures and, consequently, a gain in the mechanical performance of the asphalt mixtures. The use of HDPE on the asphalt surface provided a reduction in surface temperatures, which could be a contributing agent in the reduction of urban heat islands. [ABSTRACT FROM AUTHOR]

A high-performance composite modifier ER-SBS-T was prepared through the mixing of epoxy resin with a fast-melting styrene–butadiene–styrene modifier (SBS-T) to enhance material properties. This study evaluated the fatigue characteristics of ER-SBS-T-modified asphalt using a linear amplitude sweep test, and 70# base asphalt, SBS-modified asphalt, and SBS-T-modified asphalt were used as control groups. The fatigue life of ER-SBS-T-modified asphalt was determined according to viscoelastic continuous damage (VECD) theory. The findings indicated that as the ER-SBS-T modifier content increased, both the maximum value and the cumulative damage limit value increased, while the rate of change of decreased. At strain levels of 2.5% and 1%, the fatigue life of the modified asphalt improved with increasing ER-SBS-T content. However, at a strain level of 5%, the modified asphalt exhibited no significant trend in fatigue life across different ER-SBS-T contents. ER-SBS-T-modified asphalt with a modifier content of >10% demonstrated favorable fatigue performance suitable for practical engineering applications. [ABSTRACT FROM AUTHOR]

During the preparation of asphalt mixtures, styrene-butadiene rubber (SBR) polymers are susceptible to thermal decomposition, which can significantly impair the binder’s low-temperature performance. This study explores the potential of combining warming agents with waste materials to enhance the low-temperature properties and aging resistance of the binder. Specifically, it examines the synergistic impact of Sasobit/recycled engine oil (Sasobit/REO) composites on the rheological and physical attributes of styrene-butadiene rubber asphalt binder (SBRAB). Utilizing fluorescence microscopy (FM), bending beam rheometer (BBR), and dynamic shear rheometer (DSR), the study assesses the aging resistance and modification mechanisms of Sasobit/REO on SBRAB. The findings indicate that the incorporation of Sasobit/REO composites more effectively reduces the mix preparation temperature than either component alone. The preparation of Sasobit/REO warm mix asphalt mixtures is feasible at temperatures 20°C lower than those required for traditional hot mixtures. These composites also enhance the performance of SBRAB at both high and low temperatures, counteracting the adverse effects associated with the individual use of Sasobit or REO. This reduced short-term aging temperature is beneficial in lessening the negative impact of high temperatures on SBRAB’s performance. Moreover, the addition of Sasobit/REO composites significantly improves the thermal cracking resistance of SBRAB mixtures. The study also demonstrates that Sasobit/REO enhances the short-term and long-term aging resistance of SBRAB, paving the way for the broader application of this novel warm mix additive in the asphalt industry. [ABSTRACT FROM AUTHOR]

To investigate the rheological properties of poly(styrene-butadiene-styrene) (SBS)/tackifying resin composite high-viscosity modified asphalt, a single-factor control variable method was used to study the influence of modifiers content. The conventional properties, 60°C dynamic viscosity, 135°C rotational viscosity, and elastic recovery of the modified asphalt was systematically evaluated. Meanwhile, the rheological properties, modification mechanism, and microstructure of composite-modified, high-viscosity asphalt were thoroughly analyzed by dynamic shear rheometry, Fourier transform infrared spectroscopy, fluorescence microscopy, and atomic force microscopy. The results showed that the optimal proportion for composite modification was 7.5% SBS modifier, 0.19% stabilizer, 3% tackifier A, and 1% tackifier B. The addition of tackifiers A and B significantly improved the high-temperature performance and rutting resistance of the asphalt, satisfying the requirements of overweight traffic and above levels. After adding tackifier A, the C─ H aromatic stretching vibration at 3,042 cm−1 of the asphalt disappeared. Tackifier A increased the polarity between components, which caused coupling to occur inside the composite-modified, high-viscosity asphalt, forming a uniform network distribution among the asphalt and optimizing the compatibility between modifiers and asphalt, which improved the viscosity and performance. The network structure in the A/B composite-modified, high-viscosity asphalt system was more stable, and the root mean square roughness, Rq , of A/B2# asphalt was 1.36 nm, showing the best compatibility within the asphalt. [ABSTRACT FROM AUTHOR]

The rainy season in hot and humid areas can cause various diseases to weaken the performance of asphalt pavement. To determine the influence of rainfall on the viscoelastic properties of asphalt binder, a dry–wet cycle aging method was used to simulate the aging behavior of Gaotong base asphalt binder (GBA) and styrene–butadiene-styrene (SBS) modified asphalt binder (SBSMA), and the complex shear modulus, fatigue characteristics, and creep compliance of binders during dry–wet cycle aging were studied. The results show that the complex modulus of binders raised with the increase of dry–wet cycles time. Further, according to the simplified viscoelastic continuous damage (S-VECD) model, the damage of aged binders went up while the integrity went down sharply. Moreover, the fatigue life of SBSMA was greatly affected by aging, still far better than that of GBA. The fatigue parameters had a certain correlation with the complex modulus and they could predict the fatigue characteristics of aged binders. The creep recovery rate of GBA increased with the increase of the dry–wet cycle aging time, opposite to SBSMA. Furthermore, compared with thermal oxidative aging, the damage to the asphalt binder was worse in the later stage of dry–wet cycle aging because of the dissolution of the polar groups of binders and the continuous exposure of new surfaces. [ABSTRACT FROM AUTHOR]

Jordan's road network continues to deteriorate as a consequence of the continuous increase in traffic and the absence of adequate maintenance work. The primary objective of this study was to enhance HMA performance by using polymer-modified asphalt mixtures. The polymer modifier known commercially as Eastman (EE-2) was mixed with binder penetration grade (60–70) at a ratio of 12%. In order to investigate the performance of polymer, the dynamic creep, the resilient modulus and the stability-flow tests were performed. Marshall Mix design was utilized to prepare a total of 50 samples, of which 20 were used to determine the optimal binder content, and the remaining samples were used to determine the effect of EE-2 modifier on asphalt mixtures. The results showed that the optimal asphalt content was 4.57 percent and revealed that the addition of EE-2 polymer to asphalt cement contributed to the production of a variety of desirable properties. The most important indicator of these developments is increased rutting resistance. For instance, the total permanent deformation has decreased by 87% (8500 to 1000 μm). Conversely, addition of EE-2 has resulted in a threefold increase in the resilience modulus (from 3632 to 10590 MPa). Finally, effect of the EE-2 polymer on the stability was demonstrated by increasing the stability value by about 52% [ABSTRACT FROM AUTHOR]

Using existing resources more efficiently and effectively becomes important currently. The question of how to make the best use of resources arises in the choice between constructing new roads and improving deteriorated existing roads. It is also important to reduce the amount of consumption and cost of materials. This has emerged the need to use waste materials by recycling and reusing. In this study, a new hot-mix asphalt (HMA) mixture was developed using recycled asphalt pavement (RAP), which was obtained by excavating the surface of a road at the end of its service life, together with a waste material namely natural pozzolan (NP). The final obtained mixture was used as a wear layer on an active highway. Core specimens were extracted from the paved layer for one year and subjected to dynamic and mechanical laboratory tests. Adding NP improved the resistance of the HMA mixture under heavy seasonal effects and traffic loads. In addition, NP increased the tensile strength, making the HMA mixture more resistant to deformation than control and RAP HMA mixtures. Dynamic creep test results showed that the control asphalt mixture had the most deformation and that the RAP mixture with NP had the least. According to the laboratory results, NP addition increased the stability value of the control mixture by 40%. Especially in cold seasons, the role of NP was more evident. In the performance tests that were applied on core samples taken from the field, ITS values for September increased by 98%, and the deformation values obtained as a result of the dynamic creep test decreased by 12%. In summary, adding NP to RAP HMA improves the performance of the pavement and the cost-effectiveness of the environmentally friendly use of RAP in HMA. [ABSTRACT FROM AUTHOR]

Modified asphalt binders are still considered important in asphalt pavement. However, the comprehensive use of various modifiers is limited due to storage stability issues. Moreover, there is a scarcity of detailed analyses regarding the degree of separation for asphalt binders among each method despite the utilization of various methods to assess the storage stability of binders. Therefore, a comprehensive analysis was conducted to assess the storage stability of asphalt binder modified with a crumb rubber modifier (CRM) and styrene–isoprene–styrene (SIS), utilizing five evaluation factors following the ASTM D7173 guidelines based on four mixing methods (A: high-shear mixing method, B: low-speed agitating method, C: high-shear mixing method + low mixing method, D: low-speed agitating method + low mixing method). To produce the modified asphalt binder, the proportions of the CRM were 5% and 10% for each binder, and 10% SIS was added to all binders. The results in this study convey that (1) the addition of the modifier led to an increase in G*/sin δ with different mixing methods, but using mixing methods (C and D) for a relatively long time resulted in a lower G*/sin δ, indicating suboptimal performance; (2) through the multiple stress creep recovery (MSCR), rheological properties of Jnr and % rec exhibited trends similar to G*/sin δ evaluation, highlighting an improved elastic recovery with a higher modifier content; (3) storage stability assessment revealed consistent trends in high-shear mixing groups (A and C), while low-speed mixing groups (B and D) exhibited an elevated separation index (SI), suggesting a sensitivity to modification conditions; (4) evaluation using the MSCR method indicated that % rec with a 3.2 kPa load is effective for the sensitive assessment of binder storage stability and Jnr showed a limited sensitivity across varying loads, advocating for % rec for precise evaluation; and (5) despite permitting various tests, achieving consistent results remains challenging. Future research should explore diverse modifiers and optimal evaluation methods to enhance knowledge of binder behavior and separation dynamics. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The fatigue phenomenon significantly weakens road pavement due to repeated reloading. To enhance fatigue resistance, numerous studies have explored various additives in asphalt mixtures. This review focuses on key variables influencing the effectiveness of additives, including fibers, polymers, nanomaterials, waste materials, and biomaterials, in improving the fatigue performance of asphalt mixtures. The study initially identifies different additives and fatigue testing methods used for asphalt mixtures. It evaluates the impact of factors such as modifier content and size, base asphalt binder type, mixing processes, dispersion behavior, and testing conditions on the fatigue behavior of modified asphalt mixtures. The cost-effectiveness and environmental impact of additive application have also been assessed. Additionally, research gaps and future prospects for modified asphalt mixes are outlined. Existing studies demonstrate the benefits of additives like basalt fiber, polyester fiber, styrene–butadiene–styrene (SBS), nanosilica, crumb rubber, and biooils in enhancing the fatigue life of pavement constructions. However, challenges exist in the application of modifiers due to limited practical implications and insufficient knowledge. Further research is needed on factors such as additives' dispersity, compatibility, aging resistance, economic viability, and modifying mechanisms in morphological and micromechanical aspects to enhance the fatigue performance of the modified asphalt mixture. [ABSTRACT FROM AUTHOR]

Asphalt binder is susceptible to aging from heat, air and sunlight exposure during service, leading to pavement distresses. This study aimed to improve the aging resistance of asphalt using zinc oxide-silicate (ZOS) composites. ZOS containing 2–8 wt% ZnO were synthesized via a one-step sol-gel method and incorporated into an unmodified 70/100 penetration grade asphalt binder. The rheological properties and aging characteristics were evaluated before and after rolling thin film oven and pressure aging vessel protocols. Dynamic shear rheometry showed increased complex modulus and decreased phase angle for ZOS-modified binders, indicating improved rutting resistance. Aging indices revealed the 6% ZOS composite had the least susceptibility to oxidative aging. FTIR analysis confirmed the formation of carbonyl and sulfoxide functional groups during aging, which were mitigated by ZOS addition. Scanning electron microscopy visualized nano-scaled ZnO particles dispersed within the silica matrix and asphalt binder. The ZOS composites delayed the aging rate through physicochemical interactions between ZnO and the asphalt medium. An optimum ZOS dosage of 4–6% was found to enhance the anti-aging properties. The renewable silica-supported ZnO composites show potential as cost-effective modifiers for improving asphalt durability. [ABSTRACT FROM AUTHOR]

The demand for effective asphalt additives is growing as road infrastructure ages and more sustainable pavement solutions are needed. Tire pyrolysis oil (TPO) is an example material that has been gaining attention as a potential asphalt additive. While physical performance grade (PG) temperatures are the predominant performance requirements for asphalt binders, chemical properties are also significant in the evaluation of asphalt performance. There is a need to chemically characterize the aging of asphalt binders modified with TPO and link chemical changes in binder components to binder performance. This study compares 2%, 4%, and 8% TPO and asphalt binder blends via dynamic shear rheometry (DSR), Fourier-transform infrared (FTIR) spectroscopy, and nuclear magnetic resonance (NMR) relaxometry. The variability in the modified blends was seen by both physical and chemical testing during four different blending times (1, 60, 120, and 240 min). After blending, high and intermediate PGs were determined by physical testing. The 8% TPO blend reduced the high PG of the binder from 64 °C to 58 °C. This effect was confirmed by chemical testing through changes in carbonyl indices and NMR relaxation times. With more oil present in the binder matrix, the binder's resistance to rutting was reduced. While the high PG was hindered, the intermediate PG remained unchanged for all TPO blends. This physical similarity was mirrored in chemical testing. The chemical and physical variability along with the hindrance of the high PG temperature indicate that more treatment may be needed before TPO can be effectively applied to asphalt binders. This study suggests a correlation between physical performance and key chemical indicators. [ABSTRACT FROM AUTHOR]

SBS (styrene-butadiene-styrene block copolymer) is a thermoplastic elastomer with properties most similar to rubber. SBS asphalt modifier is mainly composed of a styrene-butadiene-styrene block copolymer with a certain amount of additives and stabilizers. SBS-modified asphalt binder has always been the most commonly used pavement material both domestically and internationally. However, conventional wet-process SBS-modified asphalt binder requires manufacturers to produce it in advance and transport it to a mixing plant for blending. This has provided an opportunity for unscrupulous businesses to reduce the amount of SBS by adding other substances, allowing inferior asphalt binder to pass inspections undetected. At the same time, conventional wet-process SBS-modified asphalt tends to undergo phase separation and experience a decline in performance as the storage time increases. However, dry-process SBS-modified asphalt can be directly added at the mixing plant, effectively addressing the issues associated with conventional wet-process SBS-modified asphalt. It also helps to reduce environmental pollution to a certain extent. This study investigates the extraction process of dry-process SBS-modified asphalt binder. It clarifies the performance and modification mechanisms of two types of dry-process SBS-modified asphalt binder at different dosages through various testing methods, including basic indicators, rheological properties, infrared spectroscopy, and fluorescence microscopy. The results indicate that due to the incorporation of oil, crosslinker, solubilizer, and other substances into dry-process SBS modifier, there is a small amount of chemical reaction with asphalt in the melting process. The high- and low-temperature properties and fatigue properties of the two dry-process SBS-modified asphalt binders at a 7% dosage are close to wet SBS-modified asphalt binder at a 5% dosage. [ABSTRACT FROM AUTHOR]

The aim of the study is to understand and achieve storage stable, compatible plastic-modified asphalt binders. In view of global plastic accumulation, the potentiality of polymeric waste plastics is evaluated as an asphalt binder modifier; providing an alternate recycling option. However, due to phase separation issues between asphalt and plastic, the usage of waste plastic is preferred through dry mixing in asphalt mixture. In this study, the compatibility of polyethylene-modified asphalt binder was assessed along with appropriate parameters that can explain the actual phase separation occurring during storage stability testing. Two types of plastics including low-density polyethylene (LDPE) and high-density polyethylene (HDPE) were blended with a PG 58-28 neat binder after assessing their melting behavior along with polystyrene (PS) and polyethylene terephthalate (PET). The impacts of polyethylene size (2.36–1.18 mm, 0.6–0.3 mm, less than 0.3 mm), blending time (30, 60, 120, 180 min), hot storage duration (0, 24, 48 h), and compatibilizers (styrene-butadiene-styrene, nanosilica, corn oil, polyphosphoric acid) on the storage stability were assessed. G*/Sinδ was used as an initial measure to assess the separation index (SI) value. The results concluded that polyethylene is observed to be inert to asphalt and phase separation persists irrespective of size and compatibilizer. Nanosilica at a dosage of 0.5% was able to partially compatibilize (SI value improved from 5.4 to 1.87) PE with asphalt. Also, in the need for better parameters to better understand the phase separation, percentage recovery, fluorescence microscopy, and black space analysis were identified as proper tests to detect phase separation. [ABSTRACT FROM AUTHOR]

This study explores the impact of adding waste vehicular crumb rubber to the commercially available warm mix additives Sasobit® and Zycotherm® on modified asphalt binders' physical and rheological properties. Various concentrations of crumb rubber (0%, 10%, 15%, and 20%) were introduced to asphalt binder samples with 2% and 4% Sasobit and 1.5% and 3% Zycotherm. The investigation employed conventional tests (penetration and softening point) and advanced mechanical characterization tests, including Superpave rotational viscosity (RV), Dynamic Shear Rheometer (DSR), DSR multi-stress creep recovery (MSCR), DSR linear amplitude sweep (LAS), and Bending Beam Rheometer (BBR). Traditional tests measured the asphalt consistency, while workability was assessed through the RV test. The results showed that the Zycotherm binders experienced a more significant penetration reduction than the Sasobit binders. Additionally, an increased crumb rubber content consistently elevated the softening point and rotational viscosity, enhancing the complex shear modulus (G*) values. Rubberized binders exhibited an improved rutting performance and low-temperature PG grades. Increasing the crumb rubber content enhanced fatigue life, with Z1.5CR20 and S2CR20 demonstrating the longest fatigue lives among the Zycotherm and Sasobit binders, respectively. Overall, Z1.5CR20 is recommended for colder climates, while S2CR20 is suitable for hot-climate applications based on extensive analysis. [ABSTRACT FROM AUTHOR]

Thermoplastic elastomers (TPEs) have emerged as promising candidates for developing cost-effective asphalt materials with superior low-temperature performance, combining the attributes of vulcanized rubber with the processing ease of thermoplastics. In this study, a novel approach involved blending high-density polyethylene (HDPE) and natural rubber (NR) with and without compatibilizers (MA) as additives for modifying asphalt 60/70 at varying percentages (3%, 5%, 7%, and 10% wt/wt). The performance of polymer-modified asphalts (PMAs) was assessed through penetration index (PI), temperature susceptibility, shear stress/shear rate, dynamic viscosity, and mechanical properties under different conditions (air and water). The findings demonstrated that polymer addition to asphalt mitigates its thermal susceptibility, imparting increased elasticity. PMAs exhibited thixotropic behavior, high yield stress, excellent gunnability, and resistance to flow on vertical surfaces. Tensile shear strength in the blends increased with polymer content, with PE70/MA outperforming PE70. Both in water and air, PE70 and PE70/MA enhanced asphalt's mechanical properties, with air proving more effective. The optimal ratios for workability were identified as 7% and 5%. Notably, PMAs displayed higher tensile strength, indicating enhanced strain tolerance before failure (cracking). Moreover, the study highlighted the potential to evaluate asphalt mixture moisture susceptibility by comparing tensile strength under wet and dry conditions. [ABSTRACT FROM AUTHOR]