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• Lignin additive extracted using H 2 SO 4 (L-S) had high phenolic content and pH value. • Asphalt with L-S additive had the lowest reduction of crossover modulus due to aging. • Incorporating L-S into asphalt reduces the increase of asphaltene fraction due to aging. • FTIR test is more sensitive in measuring the lignin antioxidant performance than DSR and GPC. The main objective of this research is to investigate the effectiveness of lignin bio-additives derived from black liquor paper pulp as asphalt antioxidants. Two lignin bio-additives, H-L and S-L, were developed by acidifying black liquor with hydrochloric and sulfuric acid. The laboratory aging procedures used in this study included the Rolling Thin Film Oven and the Ultraviolet Chamber methods. The crossover modulus (|G* c |) and linear amplitude sweep (LAS) were measured using a Dynamic Shear Rheometer (DSR). Gel Permeation Chromatography (GPC) was also used to characterize the molecular size distribution of the asphalt binder. The combination of carbonyl and sulfoxide aging indices was measured using Fourier Transform Infrared (FTIR) spectroscopy. The S-L modified binder (S-LMB) demonstrated superior aging resistance compared to both the control binder (CB) and the H-L modified binder (H-LMB) by exhibiting the lowest reduction in |G* c |. Furthermore, the LAS test results showed that S-LMB provided the best resistance to aging due to the lowest decrease in fatigue life with age conditioning, followed by CB and H-LMB, with rates of 11%, 13%, and 16%, respectively. The GPC results also confirmed the efficacy of the S-L bio-additive as an antioxidant, exhibiting the lowest increment in asphaltene proportion attributed to age conditioning. The FTIR measurements successfully captured the antioxidant capability of both H-L and S-L bio-additives, with S-L performing better than H-L. Overall, the results suggest that S-L demonstrates superior antioxidant performance compared to H-L. [ABSTRACT FROM AUTHOR]

• Recycled Paper Mill Sludge as a filler in asphalt mixture is a feasible practice. • Recycled Paper Mill Sludge modified mixtures requires less asphalt binder content. • The optimum sludge content of 0.5% have been chosen as the most practical rate. • The elemental composition and mineralogical compound of sludge were assessed. • The incorporation of sludge comparatively improved the performance of mixture. As a developing nation that moves towards the sustainability, initiatives had been taken to address the solid waste disposal problem by incorporating them into asphalt pavement construction. This study integrates the recycled material named Recycled Paper Mill Sludge (RPMS) into the production of asphalt mixture as modifier through the partial substitution of mineral filler. The usage of solid waste material in pavement construction could substantially reduce the waste production and reduces the possibility of those waste materials ending up on landfills. This paper evaluates the microscopic analysis such as XRD, XRF and the mechanical properties of asphalt mixture with the incorporation of Recycled Paper Mill Sludge (RPMS). Mechanical properties that were evaluated were indirect tensile strength (ITS), moisture sensitivity, resilient modulus, Leutner shear and dynamic creep. RPMS was added to the asphalt mixture through dry process at the rate of 0.5% and 1%. Addition of RPMS at specific rate improved the mechanical properties such as resilient modulus, Leutner shear and dynamic creep of asphalt mixture. The lapped antenna like fibre of RPMS improved the resilient modulus of asphalt mixture by acting as a reinforcing material. Furthermore, RPMS contains calcite compounds that promote the adhesion bonding between asphalt binder and aggregates which significantly improved the performance in Leutner shear test and dynamic creep test. [ABSTRACT FROM AUTHOR]

• It is feasible to use paper-based asphalt felt (RPAF) waste in asphalt mixtures. • The effects of RPAF on the rheological property of asphalt-binders is a function of temperature. • Asphalt mixtures with RPAF exhibited better moisture stability and anti-rutting property. • The fatigue life of the asphalt mixtures increased with the addition of RPAF. Paper-based asphalt felt, which is typically used as a waterproofing material, is one of the most problematic solid wastes in terms of disposal and environmental contamination. The laboratory work presented in this paper aims to propose a strategy for utilizing the reclaimed paper-based asphalt felt (RPAF) waste in hot-mix asphalt (HMA) pavements as a means to mitigate the RPAF disposal problem. A series of laboratory tests, including viscosity, modulus, rutting, and cracking, were conducted to investigate the effects of RPAF additives on the engineering performance of asphalt-binder and HMA mixes. The corresponding test results showed that the addition of RPAF improves the viscosity and high-temperature performance of asphalt-binders. However, RPAF modified asphalt-binder exhibited inferior storage stability than the virgin asphalt-binder due to the difference in density between the asphalt-binder and RPAF components. Additionally, the effect of RPAF on the rheological characteristics of the asphalt-binder exhibited high sensitivity to temperature. The differences in complex modulus and phase angle of the asphalt-binder with RPAF additives were generally more significant at elevated temperatures. Similarly, RPAF modified HMA mixes outperformed the control HMA mix in terms of resistance to moisture damage, rutting, and cracking, respectively. Overall, the laboratory test results indicated that it is feasible to utilize RPAF waste as an asphalt-binder modifier to enhance the engineering properties/performance of the asphalt-binder and HMA mix whilst simultaneously addressing the environmental issues of RPAF waste disposal. [ABSTRACT FROM AUTHOR]

• Aggregate source proved to be relevant for stripping and for moisture-induced damage. • Mixtures with the same base bitumen had stiffnesses differing in asymptotic elastic moduli. • Anti-stripping agent increased fatigue life of the investigated asphalt mixtures. • HMA with better aggregate-binder adhesiveness have shown longer fatigue life. • Adhesiveness seems to delay of microcraks when strain amplitudes are small. This study investigated the effects of aggregate-binder adhesiveness on moisture damage and on fatigue life of four different asphalt mixtures. Adhesivemeness was assessed by: (i) qualitative observation of binder stripping from the coarse aggregate's surface, incremented in this paper with digital image processing, and (ii) modified Lottman test. Fatigue damage modeling was performed, using tension-compression test results. The granitic aggregate produced mixtures with better moisture resistance and fatigue properties when compared to the phonolitic aggregate (same ranking as for aggregate-binder adhesiveness). The same was observed for mixtures with binder containing an anti-stripping agent. It was demonstrated that mixtures with better aggregate-binder adhesiveness have greater fatigue life. [ABSTRACT FROM AUTHOR]

• Lignin as partial replacement of bitumen for producing bio-asphalt materials. • Raw material and production process of lignin significantly affect the performances of bio-materials. • Laboratory multi-scale approach and real-scale applications of bio-materials are discussed. • Life-cycle assessment and economic analysis are addressed. • Lignin-based asphalt materials represents a promising technical and environmentally friendly solution. Nowadays, one of the most interests of modern society is to replace increasingly larger quantities of petroleum-derived products, which is a non-renewable source progressively depleting, so promoting both environmental and economic benefits. In this context, the practice to employ renewable sources to replace part of the bituminous materials is an effective approach in pavement engineering. Among different biomasses which are recognized as possible sources mixable with bitumen, lignin can represent a valid material. Lignin is a natural resource commonly deriving from the by-product of the production of pulp and paper industry. It is the second most common biopolymer on Earth and represents a potentially attractive alternative as partial substitute of bitumen. However, in order to understand the environmental and technical feasibility of the application of lignin in bituminous pavement applications, a multi-scale approach must be adopted. For this purpose, the paper aims at providing an overview of the use of lignin as renewable source in bituminous binders and mixtures, by investigating chemical, rheological and mechanical properties of lignin modified asphalt materials. Moreover, based on the available literature, field application experiences and Life Cycle Assessment (LCA) analysis are also discussed. [ABSTRACT FROM AUTHOR]

The objective of this paper is to investigate the microstructure of high-viscosity modified asphalt binder (HVA) containing high-content polymers and its effect on fatigue performance, as well as the applicability of different analytical methods and failure criteria of linear amplitude sweep (LAS) test to HVA. In this paper, two types of HVAs with different polymer contents, a commercial HVA, a conventional polymer-modified asphalt binder, and a base asphalt binder were first prepared or selected. Fluorescence microscopy tests, time sweep tests, and LAS fatigue tests were then performed on these binders. Finally, the fatigue properties of the different binders were analyzed in depth using different analytical methods and failure criteria. The results show that the polymers in HVA crosslink with each other to form a strong cross-linking structure, and the phase inversion of the polymers renders them into a continuous phase, which significantly improves the fatigue damage resistance of the HVA; moreover, the evolutions of stress with shear strain for the fatigue process of HVAs is related to the polymer network. Besides, the two-dimensional damage characteristic curve (DCC) cannot accurately reflect the evolution of the fatigue performance of HVA, and this paper suggests the use of a three-dimensional DCC curve with strain information. Furthermore, the 35% reduction in C 0 in the dissipative energy method is not a suitable failure criterion, a more accurate fatigue performance ranking can be obtained by using the yield stress as the failure criterion. Although the fatigue resistance of HVA after yield stress is theoretically considered using the pseudo-strain energy approach, HVA does not show a peak of stored pseudo-strain energy even when the strain is increased to 60% in the LAS test. Therefore, the maximum strain value (30%) in the standard LAS test is not sufficient in characterizing high-polymer HVAs because there is not enough fatigue accumulation of HVAs in this range, consequently, the maximum shear strain parameter in the LAS experiment needs to be reconsidered. • Polymer morphology and its crosslinking networks in HVA with high-content polymers were analyzed. • The fatigue properties of HVAs based on LAS test and different analytical methods are compared. • The fatigue crack length and its evolution of HVA are characterized. • The deficiencies of the LAS test to evaluate the fatigue resistance of HVA and suggestions for modifications are presented. [ABSTRACT FROM AUTHOR]

Recycling of UV-aged asphalt has been a hot research issue. In this paper, waste cooking oil, plasticizer, toughener, and petroleum resin were used as raw materials for asphalt rejuvenator. This paper explores the effect of regeneration conditions on the regeneration effect of UV-aged asphalt binders through high-temperature rheology and chemical compositions. The paper also attempts to reveal the regeneration mechanism of asphalt binder regeneration using waste cooking oil. Dynamic shear rheology (DSR) and fourier transform infrared (FTIR) spectroscopy assess high-temperature rheological properties and chemical compositions. The Pearson correlation coefficient relates the rheological parameters to the chemical microstructure. And the functional relationship between carbonyl-corrected peak area and aging factor Ai of recycled asphalt and high temperature rheological parameters were established. Molecular simulation investigates WCO-recycled asphalt binder micro-morphology and adsorption mechanisms. The results showed that significant changes in the carbonyl and sulfoxide peak areas affected the high-temperature rheological properties. Regeneration conditions significantly affect asphalt regeneration effectiveness. WCO reduces C O and S O groups, crucial in asphalt viscoelastic behavior. Molecular interaction analysis reveals WCO's regenerative mechanism. This work emphasizes integrating molecular structure, chemical composition, and macroscopic properties in asphalt binder research, providing insights for sustainable pavement practices. • The content of C=O and S=O are the main factors determining the recycling effect of WCO recycled asphalt. • WCO rejuvenator changes the molecular structure of aged asphalt. • The -OH group of WCO increases the interaction between WCO molecules and aged asphalt molecules. [ABSTRACT FROM AUTHOR]

In this paper, data from the PURWheel-G2 , a rubber tire wheel tracker, was utilized alongside several techniques to better understand isolation of the effects of moisture on asphalt rutting. Techniques commonly used to interpret wheel tracking data, particularly to evaluate moisture damage, were summarized and used to evaluate over 150 PURWheel-G2 tests where wet and dry pairs of tests were conducted to directly isolate the effect of moisture on rutting. Among all the available wheel tracking analysis techniques and models for moisture evaluation, there lacks a consensus approach, and available approaches vary widely highlighting the need for a standard test method. The rubber tire wheel tracker presented in this paper aims to take a step towards developing test protocols to isolate moisture damage. The ability to measure the effects of moisture on rutting is a feature that other existing wheel tracking methods cannot do on their own. • Rubber-tire wheel tracker tests were evaluated to isolate the effects of moisture. • Over 150 PURWheel-G2 tests in wet and dry conditions were conducted. • There is no consensus on how to analyze wheel tracking data for moisture evaluation.. [ABSTRACT FROM AUTHOR]

The increasing volume of waste rubber generated from end-of-life tyres has raised significant concerns regarding the safe and sustainable recycling and reuse of this material. A viable solution is to incorporate waste rubber into asphalt mixtures, which contributes to recycling waste tyres and promotes the sustainability and resilience of pavement infrastructure. In recent years, Crumb Rubber-Stone Mastic Asphalt (CR-SMA) mixtures have received considerable attention due to their remarkable performance. However, the feasibility of implementing CR-SMA in the field on a large scale requires further investigation. This paper aims to evaluate this matter by reviewing the mix design practices of CR-SMA, assessing the performance characteristics of CR-SMA, and identifying gaps and potential areas for improvement. The gaps related to various factors like aggregate gradation, compaction technique, processing temperature, CR grains size and their concentration, and binder content have been identified and discussed in the paper. In addition, the key performance characteristics of CR-SMA mixtures, including binder drain-down, moisture susceptibility, permanent deformation, and fatigue cracking, are evaluated. • Review history of waste tyre rubber in bituminous mixtures, tracing its evolution. • Explore the mix design practices of Crumb Rubber-Stone Mastic Asphalt (CR-SMA). • Investigate the mechanical properties and performance of CR-SMA. • Discuss the influence of CR characteristics on SMA performance. • Critically highlight CR-SMA research gaps, providing direction for future studies. [ABSTRACT FROM AUTHOR]

The effects of ageing on pavement performance are significant, particularly in terms of fatigue cracking. South Africa has the 10th longest road network in the world, requiring innovative approaches to road construction due to severe budget constraints. Innovative solutions such as thin asphalt concrete layers for surfacing, result in unique ageing rates of the layers, which, in general, have a higher incidence of fatigue cracking than, for example, thicker asphalt concrete layers used in other parts of the world. The objective of this paper is to evaluate how ageing mechanisms affect various asphalt binder properties, and whether they affect them to the same extent or not. Furthermore, the objective of the paper is also to determine the accuracy of the Rolling Thin Film Oven Test (RTFOT) in simulating short-term ageing in the field. The RTFOT provides a relatively good indication of short-term ageing, according to this multi-decade ageing study, and the effect on the asphalt binder properties used as ageing indices depends on the specific property chosen for comparison before and after ageing. • From 2001 to 2012, the prevalent surfacing in South Africa was a dense-graded asphalt mix with 50/70-grade asphalt binder. • Asphalt binders were consistent over 2001 to 2012, originating from four South African refineries. • A short-term ageing method in the laboratory cannot emulate the reaction kinetics during manufacturing and placement. • Binder properties such as penetration and softening are affected to different extents in an oxidation / ageing environment. • The rolling thin film oven provides a good indication of ageing under typical conditions of manufacturing and laying. [ABSTRACT FROM AUTHOR]

Direct injection modifiers revealed vast development potential because of their convenience utilization and no need for professional equipment. However, different characteristics of each direct injection modifier fluctuate significantly on the mixing process and road performance of their modified asphalt mixtures. The purpose of this paper is to evaluate the effectiveness of two novel asphalt rubber pellets (ARP) and asphalt desulfurized rubber pellets (ADRP) in improving the performance of asphalt mixtures. Firstly, this paper used orthogonal experimental design method to determine the priority order of the influencing factors on direct injection modifiers (ARP and ADRP), and further optimized the mixing technology of asphalt mixtures containing direct injection modifiers. Then, using base asphalt, commercial asphalt rubber (AR) and SBS (styrene-butadiene-styrene block copolymer) modified asphalt as control groups, the road performance of five asphalt mixtures was evaluated. Finally, the volatile organic compounds (VOCs) release characteristics of the asphalt mixtures were quantitatively analyzed. The results indicated that the priority order of factors affecting the ARP and ADRP is digestion time > dry mixing time > mixing temperature, and the optimal mixing process parameters are dry mixing for 90 s, mixing temperature of 180 °C, and digestion time of 90 min. Additionally, road performance of ADRP modified asphalt mixtures (ADRP-AM) is superior to that of ARP modified asphalt mixture (ARP-AM), which reaches or even exceeds the road performance of asphalt rubber mixtures (AR-AM) and SBS modified asphalt mixtures (SBS-AM) prepared by wet process. The five asphalt mixtures demonstrate the similar VOCs composition, and the total concentration of VOCs emissions is ARP-AM > AR-AM > ADRP-AM > B-AM > SBS-AM. P-/m-xylene, acetone, benzene, ethylbenzene and substances containing chlorine emerge high concentration for the VOCs composition of the five asphalt mixtures. This research can provide technical support for promoting the widespread application of direct injection asphalt rubber pellets. • Mixing technology of asphalt mixtures containing direct injection asphalt rubber pellets were optimized. • Road performance of asphalt mixtures containing direct injection asphalt rubber pellets were investigated. • VOCs of asphalt mixtures containing direct injection asphalt rubber pellets were evaluated. [ABSTRACT FROM AUTHOR]

Modified bitumen is a critical material to ensure the durability of asphalt pavements. Traditional polymer-modified bitumen (PMB) has been widely researched and applied in the past two to three decades. Recently, a high-content SBS (Styrene-Butadiene-Styrene) polymer-modified bitumen (HSBSMB) with a higher SBS content of up to 7–9% by weight has started attracting interest from researchers. There are, however, still few specifications or technical guidelines for HSBSMB. To gain a better understanding of HSBSMB, the composition and structure of typical polymer SBS and base bitumen, the micromorphology and micromechanics of HSBSMB, its rheological and aging characteristics, as well as its asphalt mixture and field pavement performance were reviewed comprehensively in this paper. The content covered in this paper is primarily derived from 210 pertinent papers published between 1990 and 2023 in two databases, Web of Science and Google Scholar. It appears from our review that HSBSMB has a stronger internal polymer network than conventional SBSMB and thus exhibits better resistance to rutting, fatigue, and cracking as well as better aging resistance. Furthermore, findings from both laboratory scale and field pavement scale indicate that HSBSMB not only offers higher performance and durability but also leads to reduced pavement structural layer thicknesses in ensuring performance. However, many issues and challenges still remain before HSBSMB will become a viable option for large-scale application in road infrastructure, aspects such as the mechanism of its internal structural changes, the optimization of methods for evaluating its rheological properties, the life cycle assessment of its long-term benefits, as well as the storage stability and workability of HSBSMB. It is hoped that this review will contribute to a better understanding of HSBSMB and promote its application. • The chemical properties of SBS polymer and base bitumen as well as their interactions were comprehensively summarized. • The mechanisms of SBS in bitumen and polymer phase inversion were discussed under different microscopy techniques. • The current standard rheological evaluation methods may need to be improved for high-content SBS polymer-modified bitumen. • High-content SBS polymer-modified bitumen exhibits better resistance to rutting, fatigue, cracking, and aging. [ABSTRACT FROM AUTHOR]

• SAXS is an advantageous technique for analyzing the microstructure of asphalt. • The primary factor responsible for microstructural changes is the aggregation of micelles. • The microstructure of recycled asphalt is mainly affected by the mass ratio of old and new asphalt. The microstructure of asphalt plays a crucial role in determining its overall performance. However, the lack of comprehensive research on parameterizing the microstructure of asphalt has hindered the establishment of a clear relationship between microstructure and macroscopic performance. To address this gap, this paper conducted a study involving small-angle X-ray scattering (SAXS) experiments to investigate the changes in the microstructure of asphalt during aging and regeneration processes. The SAXS experimental results were then subjected to fitting using the Unified function, enabling us to derive key microstructural parameters. The SAXS data profiles obtained from virgin, aged, and recycled asphalt samples exhibit a remarkable degree of similarity, suggesting that their microstructural features are highly comparable. Additionally, the scattering characteristics observed in the SAXS data point to the presence of secondary structure scatterers within the asphalt samples. The presence of secondary structure scatterers suggests that the asphalt samples consist of microstructural entities, such as micelles or aggregates, which form the basis for the scattering patterns observed. During the aging of asphalt, the size of micelles and the heterogeneity of their sizes undergo a progressive increase. Simultaneously, the surface activity of these micelles gradually diminishes. However, a notable reduction in micelle size and size heterogeneity is achieved when regenerating aged asphalt using virgin asphalt. Furthermore, the surface activity of micelles is improved through the regeneration process. On the contrary, the rejuvenator used in this study did not exhibit a significant restorative effect on the microstructure of aged asphalt. Rheological analysis indicates that the observed viscoelastic changes in asphalt during aging and regeneration align with microstructural variations, but the effect of the rejuvenators on viscoelasticity do not correlate directly with their impact on microstructure. The differences between rejuvenators in improving the properties of aged asphalt cannot be solely inferred from their effect on microstructure. The findings in this paper contribute significantly to our understanding of asphalt microstructure and its evolution during aging and regeneration processes. [ABSTRACT FROM AUTHOR]

• The composition and fundamental principles underlying ECAC are introduced. • The key aspects related to the design and preparation of ECAC are summarized. • The multi-functionality and potential practical applications of ECAC are presented. • The insights and guidance for developing ECAC are proposed. Electrically conductive asphalt concrete (ECAC) is an innovative material that offers numerous possibilities by directly incorporating functional additives (such as metal-based or carbon-based materials) into asphalt binder and mixing it with traditional aggregates and mineral filler. With such a strategy, ECAC possesses a high electrical/thermal conductivity, making it an ideal candidate for sustainable repair methods based on induced heating-healing, snow and ice melting systems on pavements, and piezoresistive sensors for traffic detection in pavement engineering. This paper aims to provide a systematic review of the design and development of ECAC, with a particular focus on the advancements made over the past decade (from 2013 to 2023). The review begins by introducing the composition and fundamental principles underlying ECAC. Subsequently, it summarizes the key aspects related to the design and preparation of ECAC. Moreover, this paper delves into the remarkable multi-functionality exhibited by ECAC, showcasing its potential in practical applications. Through examining various case studies, the review highlights the successful utilization of ECAC in diverse scenarios. This review work can serve as a valuable resource, offering insights and guidance for developing ECAC in the context of smart and sustainable pavement construction. [ABSTRACT FROM AUTHOR]

• Study found how multiple factors influence asphalt mixture's pore characteristics evolution. • Explored mesoscopic pore characteristics and macro mechanical strength correlation. • Built on AASHTO T283 and JTG E20-2011, proposed mesoscopic moisture-sensitivity method for asphalt. This paper explored the mesoscopic pore characteristics of asphalt mixtures by considering the coupling effects of grading segregation, dynamic pore water, and salt erosion, utilizing CT scanning technology. The study yielded the following key findings: 1) Under the coupling effects of grading segregation, dynamic pore water, and salt erosion, the sample with heavy segregation of coarse aggregate (HC) exhibited the highest variation in porosity, followed by the sample without gradation segregation (D), while the sample with heavy segregation of fine aggregate (HF) showed the least change. 2)The influence of gradation segregation on different mesoscopic pore characteristics demonstrated significant dispersion before and after the coupling effects of multiple factors. 3)From a mesoscopic scale perspective, this paper proposes a method to assess moisture sensitivity. The results obtained through this method indicate that the coordination number (CN) exhibits significantly stronger moisture sensitivity compared to other mesoscopic pore parameters. [ABSTRACT FROM AUTHOR]

• The morphologies of aggregates can be quantified using photography and processed through ImageJ. • The number of aggregates and volume of mortar in an asphalt mixture is enough to predict its porosity, stiffness, stability, and flow. • New design models enable to select optimal aggregate's number and mortar's volume to achieve desired performance of asphalt mixtures. • New design models help checking whether one asphalt mixture fulfils performance requirements. Conventional asphalt mix design methods require numerous experiments to verify the efficacy of various recipes, resulting in significant time and labour costs. Therefore, there is a need for an alternative method that is both efficient and convenient. To address this issue, this paper proposes a novel asphalt mix design method that reduces the reliance on time-consuming and resource-intensive physical and mechanical tests to determine the properties of new asphalt mixtures. The method focuses on the quantity of aggregates and the volume of mortar to estimate the air voids content, resilient stiffness modulus, Marshall stability, and flow requirements in accordance with industry standards. Statistical analysis shows that the key properties of asphalt mixtures are primarily influenced by the number of aggregates and volume of mortar. Nomographs are provided to predict these properties based on the mixture's gradation and mortar volume. The proposed method's feasibility is demonstrated by accurately predicting the gradations and properties of six different mixtures. Additionally, the paper suggests the use of 3D models for asphalt mixtures, allowing for the observation of aggregate distribution and air voids before testing the mixtures' mechanical properties. [ABSTRACT FROM AUTHOR]

[Display omitted] • The stability of SDBS emulsified asphalt is investigated using the MD method. • Sulfonic acid root position affects the stability of SDBS emulsified asphalt. • 4-1ΦC12S was effective in enhancing the stability of SDBS emulsified asphalt. • 4-1ΦC12S emulsified asphalt has the better thermal stability. Emulsified asphalt systems require emulsifiers to reduce oil–water interfacial energy generation to improve their stability. In this paper, the effect of the molecular structure of the SDBS emulsifier on the stability of emulsified asphalt was investigated using microscopic simulation (MD) and macroscopic tests. The effect of the molecular structure of asphalt emulsifiers on the stability of emulsified asphalt was quantified by varying the position of sulfonic acid roots in SDBS (2-1ΦC12S, 3-1ΦC12S, 4-1ΦC12S). The macroscopic tests included conventional, laser particle size tests and differential scanning calorimetry tests. The simulation results showed that 4-1ΦC12S reduced the oil–water interface energy the most and was the most hydrophilic, forming a more stable emulsified asphalt system; 2-1ΦC12S and 3-1ΦC12S were less stable due to the spatial site resistance effect of the sulfonic acid root position too close to the alkyl chain end. The test results showed that 4-1ΦC12S emulsified asphalt, with the smallest volume mean particle size, had the best thermal stability. Therefore, the isomer type of SDBS has a greater influence on the stability of emulsified asphalt, and 4-1ΦC12S has a better emulsification effect. The results indicate that future molecular structure synthesis of emulsifiers needs to fully consider the effect of isomers of emulsifiers on the emulsification effect, and the results of this paper can provide a theoretical basis for the future synthesis of high-performance emulsifiers. [ABSTRACT FROM AUTHOR]

• "Epoxy recycling" technology was used to produce mixtures containing 100% RAP. • The optimal epoxy proportion was determined to be 30% through Tukey's comparison. • G f 1 or CRI is valid for characterizing cracking behaviors of epoxy asphalt mixture. • A new SCB index (CRCS) was established through principal component analysis. • CRCS can effectively evaluate the cracking resistance of epoxy-recycled mixtures. Despite the recycling of reclaimed asphalt pavement (RAP) providing great economic and environmental benefits, conventional technologies exhibit poor cracking resistance and cannot achieve high RAP content. The major objective of this paper is to evaluate the cracking resistance of recycled mixtures containing 100% RAP using epoxy asphalt, and to determine an optimal production method. In this paper, the effects of temperatures, epoxy proportions, and gradations on cracking resistance of epoxy-recycled mixtures with 100% RAP were explored through semi-circular bending (SCB) tests, and the mechanism was explained by laser scanning confocal microscopy (LSCM) tests. Subsequently, the validity of SCB parameters was examined using statistical analysis, and a new index (Cracking Resistance Comprehensive Score, CRCS) for evaluating the cracking resistance of epoxy-recycled mixtures was proposed through principal component analysis (PCA). The results indicate that the graded mixture with an epoxy proportion of 30% could be the best solution to recycle 100% RAP, which can restore the cracking resistance to the level of virgin mixtures, outperforming the conventional recycling technique. Statistical analysis shows that temperatures and epoxy proportions have significant effects on SCB parameters, and the fracture energy until failure (G f 1 ) or crack resistance index (CRI) is valid for characterizing the cracking behavior of epoxy asphalt mixtures. Moreover, CRCS contains over 90% of the original information and effectively identifies the effects of temperatures, epoxy proportions, and gradations, which can be applied to evaluate and rank the cracking resistance of epoxy-recycled mixtures. [ABSTRACT FROM AUTHOR]

• Crumb rubber modified asphalt binder (CRM) could be applied for hot recycling. • The process of aged asphalt mixed with CRM is almost physical blending. • The optimal proportion of CRM and aged asphalt was 1:1. • At the extremely low-temperature, CRM and RA were both recommended. The stabilized crumb rubber modified asphalt is gaining attention from the researchers because of its excellent road performance and the environmental-friendly characteristic. Traditionally, the high-temperature performance of the hot-recycling asphalt binder was improved by adding low-viscosity recycling agent. In this paper, the stabilized crumb rubber modified asphalt was studied to investigate its improvement on physiochemical and rheological properties of the hot-recycling asphalt binder, especially high-temperature performance compared with traditional low-viscosity recycling agent. Three types of asphalt with different ingredients were investigated in this paper: (1) asphalt binder contains aged asphalt and crumb rubber modified asphalt; (2) asphalt binder contains aged asphalt and recycling agents; (3) asphalt binder contains aged asphalt, crumb rubber modified asphalt and recycling agents. The matrix asphalt, aged asphalt and stabilized crumb rubber modified asphalt was set as the control group. The physiochemical properties were evaluated by Fourier Transform Infrared Spectroscopy (FTIR), Gel Permeation Chromatography (GPC) and Atomic Force Microscopy (AFM). Moreover, the rheology experiments such as Dynamic Shear Rheometer (DSR) and Bending Beam Rheometer (BBR) were carried out to assess the practical performance of the three types of asphalt binder. In conclusion, it could be found that the mixing condition of different ingredient in the asphalt binder was mainly caused by physical mixing. Asphalt binder contains crumb rubber modified asphalt and aged asphalt was recommended considering the high and low-temperature performance. The optimal proportion was: 50% crumb rubber modified asphalt and 50% aged asphalt considering the economic benefits and rheological behaviors. In the extremely low-temperature environment, the high and low performance of crumb rubber modified asphalt and recycling agents in hot-recycling field still needs more investigation. [ABSTRACT FROM AUTHOR]

• Relationship between compaction degree and tensile strength is found. • Evolution of 3D fractal dimension of air voids is determined. • Tensile strength is related to complexity of air void morphology. The compaction of asphalt mixtures creates different tensile strengths throughout the asphalt mixture and is thus of importance to ensure durable pavement performance. Asphalt mixtures are composite materials. Therefore, it is necessary to analyse the relationship between the microstructural characteristics and the mechanical performance of asphalt mixtures at different DoCs. In this paper, the 3D microstructures of the asphalt specimens were reconstructed by means of Digital Image Processing (DIP) techniques based on X-ray Computed Tomography (X-ray CT) scanning. Results from the Indirect Tensile Test (ITT) were used to determine the tensile strength of the asphalt specimens. The results show that the relationships between the DoC and the tensile strength as well as the fracture energy are not linear for asphalt specimens at the same testing temperature. This indicates the occurrence of over-compaction during the compaction process. In order to reveal the mechanism of the over compaction at the microscale, the 3D fractal dimension of air voids and aggregates were derived. The 3D fractal dimension of the air voids is variable and constant at first and then becomes smaller during the compaction process. The complexity of the air void morphology is related to the tensile strengths and a hypothesis based on the evolution of 3D fractal dimension of the air voids is proposed in this paper to explain this phenomenon. The results of this research help to increase the understanding regarding the mechanism of over compaction based on the microstructure of the asphalt specimens. [ABSTRACT FROM AUTHOR]

• This paper developed a new rejuvenator based on the Crystal Nucleus Dispersion Theory. • Orthogonal test was used to determine the composition of asphalt rejuvenate agent. • The aging resistance of the new rejuvenate agent was better than present rejuvenators. This paper developed a new rejuvenator based on the Crystal Nucleus Dispersion Theory and evaluated the aging performance of the new rejuvenator. The component conditioner was selected based on the chemical composition and colloidal stability index of the asphalt. The association degree, colloidal particle size, particle size distribution and conductivity of asphaltene were considered to select the compatibilizers. The wax crystal dispersant was chosen based on the distribution and fractal dimension of wax crystal. Orthogonal test was used to determine the composition of asphalt rejuvenate agent and a new asphalt rejuvenate agent was prepared. The aging resistance of new rejuvenate agent was evaluated through the quality change and viscosity ratio after the thin film oven test (TFOT). The results indicate that the catalytic cracking slurry A, which was rich in aromatic, improves the colloidal stability of aged asphalt significantly. Dodecyl benzene sulfonic acid, which has acidic groups of high activity, reduces the association degree and disperses asphaltene aggregates into smaller units. The wax crystal dispersant can disperse coarse wax crystals into fine and uniform wax crystal particles. The fractal dimension of wax crystal increases from 1.08 to 3.26 and have a good exponential relationship with the low temperature ductility of asphalt. The mass loss and viscosity ratio of new rejuvenate agent were 1.12% and 1.28%, which were lower than the present rejuvenate agent. The aging resistance of the new rejuvenate agent was better than present rejuvenators. [ABSTRACT FROM AUTHOR]

• The photocatalytic decomposition test system of asphalt mixture is developed. • The asphalt mixture with good photocatalytic decomposition performance is designed. • The attenuation tendency of photocatalytic decomposition performance is revealed. In this paper, by designing the UV irradiance, the compositions and the initial concentrations of automobile exhaust, an asphalt mixture test system – photocatalytic decomposition of automobile exhaust performance (AMTS-PDEP) was developed based on the photocatalytic mechanism of titanium dioxide (TiO 2). Testing method and calibration method of test data were also proposed in this paper. Accumulative decomposition ratio (ADr) was used as the evaluation indicator of photocatalytic decomposition of automobile exhaust performance (PDEP) and the influencing factors of PDEP were proposed. Based on the mechanical behavior and PDEP, the design method of asphalt mixture material composition was developed and the attenuation law of PDEP was also demonstrated. The results show that the PDEP of anatase TiO 2 is much better than Rutile TiO 2. The PDEP of asphalt mixture with 0.3 μm TiO 2 is better than other particle sizes. Affected by particle adhesion, the PDEP of asphalt mixtures with 3.5% content of TiO 2 reaches the maximum value. The PDEP has positive correlations with volume (VV) of asphalt mixtures, irradiance and temperature. It is recommended that anatase TiO 2 (0.3 μm) is used as the photocatalyst, the optimum TiO 2 content is 3.1%, TPS modified bitumen is used as the binder, and porous asphalt concrete with a nominal maximum aggregate size of 13 mm (PAC-13) is used as the optimal structural carrier. The PDEP of asphalt mixture decreased with the increase of test times, but it returns to its original level immediately after simply rinse, and repeated rinse does not reduce the PDEP. The PDEP of asphalt mixture decreases with the increase of the pollution index or the decrease of VV caused by compacting. [ABSTRACT FROM AUTHOR]

• Molecular dynamic simulations were used to study glass forming process of asphalt. • Glass transition of asphalt spans a wide temperature range from ca. 400 K to ca. 250 K. • Non-Arrhenius temperature dependence of viscosity implies a transition at ca. 400 K. • Breakdown of Stokes-Einstein relation verifies the transition at ca. 400 K. • Viscoelastic liquid-Newtonian liquid transition at ca. 400 K explained by cage effect. Glass transition temperature (T g) is a significant parameter that determines the viscoelastic properties of asphalt. However, the understanding of glass transition process of asphalt is ambiguous, especially at the molecular level. In this paper, molecular dynamic (MD) simulations were used to help understanding the glass forming process from the viewpoint of glass forming liquid. The temperature dependence of volumetric properties, such as free volume, fractional free volume, specific volume and coefficients of volume thermal expansion etc., for AAA-1 asphalt were computed. Results show that there are two transition temperatures with temperature decreasing from 575 K to 50 K, i.e., one is T g at ca. 250 K, the other is ca. 400 K. The non-Arrhenius type temperature dependence of viscosity and the breakdown of Stokes-Einstein relation imply that the transition at ca. 400 K is responsible to the liquid–liquid transition of asphalt from viscoelastic liquid to Newtonian fluid. Furthermore, molecular trajectory demonstrated that at ca. 400 K, AAA-1 asphalt system experienced the transition from non-ergodic local thermal vibrations and restricted movement to temperature-independent ergodic movement, and this observation verified that the liquid–liquid transition of asphalt did occur at ca. 400 K. Namely, at temperatures higher than 400 K, the rearrangement process of asphalt colloid cage is a temperature-independent ά-relaxation, and in the temperature range from 400 K to 250 K, the relaxation associated with diffusional movement is a slow α-relaxation, i.e., structure relaxation of glass transition, and at temperatures lower than 250 K, asphalt is truly frozen glassy. Moreover, the good agreement between the rheological experiments and simulation results demonstrated that the MD results are reliable. This paper helps understanding microscopic picture of glass forming asphalt and its relaxation mechanisms with temperature, which could enable new additives and new additive strategies to modify asphalt and facilitate crude oil exploitation, transportation and refining processes, etc. [ABSTRACT FROM AUTHOR]

• Clarify the effects of mixture gradation and polishing on nanoindentation results. • Characterize the age-hardening behavior of asphalt mixtures using nanoindentation. • Describe the vertical aging gradient in asphalt mixtures by nanoindentation. Understanding the aging behavior of asphalt mixtures is of great significance to the design, construction and maintenance of asphalt pavements. Numerous studies have been conducted on the aging phenomenon and its effects on mixture properties. However, conventional testing methods focus mainly on the global view or average value of the performance of aged mixtures, while the inner aging gradients are seldom addressed. The aging gradient, referring to the differences of aging effects in asphalt mixtures due to different accessibilities to aging conditions, represents the true aging behavior of asphalt mixtures. Hence, a micromechanical testing technique, nanoindentation, was used in this paper to investigate this issue. The effects of mixture gradation and polishing in sample preparation process on nanoindentation results were explored first. Then the vertical changes of modulus of asphalt mastic in asphalt mixture samples were characterized by nanoindentation to describe the aging gradient in different aged mixture samples. Dynamic modulus test was also performed for data supplement and comparison. Results show that gap-graded mixtures are suitable for nanoindentation test and a careful and standard polishing treatment will not affect the reliability of nanoindentation data. Nanoindentation can well characterize the age-hardening behavior of asphalt mastic and the aging gradient in long-term aged asphalt mixtures is approximately in a logarithmic curve form. Nanoindentation modulus results indicate that 8d of laboratory long-term aging in this paper can only affect the upper sections of dense asphalt mixtures. This paper suggests that nanoindentation can achieve a quantitative, mechanical and precise characterization of aging gradient in asphalt mixtures and is therefore promising in further research of asphalt materials. [ABSTRACT FROM AUTHOR]

• This paper establishes a 3D meso -finite element (FE) model based on an aggregate random placement procedure to simulate the freeze-break behavior of asphalt concrete samples. • An effective modulus equation of asphalt mortar, which accounts for the ductility (at 5℃) and brittle point of modified asphalts as dominant factors, is proposed. • The freeze-break temperature of modified asphalt concrete can be predicted, based on the brittle point and ductility (at 5℃) of modified asphalt. Hydraulic asphalt concrete is widely used in pumped storage power stations and other anti-seepage engineering. The low-temperature freeze-break of asphalt mixtures is a rather complex phenomenon significantly affected by the ductility (at 5℃) and the brittle point of asphalt binder. In order to achieve better crack resistance at low temperatures, the influence of ductility and brittle point on low-temperature fracture becomes a major problem. This paper firstly proposes an effective modulus equation of asphalt mortar, which accounts for ductility and brittle point of modified asphalts as dominant factors. Then, a three-dimensional (3D) mesoscale finite element (FE) model, which considers this equation and the damage evolution of the asphalt mixture from linear viscoelastic (LVE) to elastic-brittle due to cooling, is established through an aggregate random placement procedure to simulate the freeze-break behavior of asphalt concrete samples in the thermal stress restrained specimen test (TSRST). The numerical simulation results of thermal stress are in good agreement with the previously published TSRST thermal stress data, and this verifies that our model is effective. Furthermore, the proposed model can predict the freeze-break temperature of asphalt mixture with good accuracy, and well describe the mesoscale thermal stress, strain, and damage distributions. [ABSTRACT FROM AUTHOR]

[Display omitted] • Vibration acceleration was used to simulate the erosion process of spilled oil on the pavement. • Different methods were used to characterize the effect of oil erosion on the adhesion properties of asphalt. • The mechanism of alteration of asphalt viscosity by oil erosion is explained from a microscopic point of view. In order to study the long-term effects of leaking oil on the adhesion properties of asphalt pavements, some tests were conducted in this paper on asphalt eroded by leaking engine oil of different time duration. The effects and mechanism were investigated by physical property tests, scanning electron microscope (SEM) tests, infrared spectroscopy (FT-IR) tests and gel permeation chromatography (GPC) tests. The physical property tests show that the adhesion capacity of asphalt binder corroded by engine oil is significantly reduced; the change rate gradually slows down with the extension of corrosion time; the viscosity at the same temperature declines, and the sensitivity of viscosity change with temperature is reduced. Microscopic tests show that the location of characteristic peaks in asphalt after oil corrosion does not change much, but the intensity changes significantly; the process of asphalt subjected to oil corrosion is a physical dissolution process; leaking oil corrosion will form cracks on asphalt binders, resulting in the increase of small molecules and the loss of large molecules. Finally, Grey Relational Analysis is used in the paper to correlate the viscosity of asphalt with the functional groups and molecular weight of asphalt and their distribution before and after oil corrosion, and it is found that oil corrosion mainly affects the asphalt corrosion performance by changing the Weight average molar mass (M w), Small molecular size (SMS) and C C of asphalt. [ABSTRACT FROM AUTHOR]

[Display omitted] • The properties of vegetable oils and their applications in asphalt are summarized. • Functionalized vegetable oils have better modification or regeneration effects. • Functionalized vegetable oils may interact with asphalt physically and chemically. • Biopolymers can replace traditional counterparts in asphalt modification. • Vegetable oil-based additives are used as rejuvenators, fluxing agents or modifiers. Vegetable oils and their derivatives have shown great potential as modifiers or rejuvenators for use in asphalt materials with promising performance. Due to the environmental and economic benefits, investigations on using vegetable oils in an effective way to enhance performance and promote interaction with asphalt materials have been further conducted in recent decades. This paper reviews the state of the art on the applications of vegetable oils and their derivatives as bio-additives for use in asphalt binders, which includes the use of plant based-oil (vegetable oil and waste vegetable oil), functionalized vegetable oil (epoxidized, transesterified, and acrylated vegetable oils), and vegetable oil-based polymer (soybean oil-based and castor oil-based biopolymer). Emphasis is given on the continuous optimization of vegetable oil's chemical structure to improve its compatibility and interaction with asphalt. The advantages and disadvantages of using various vegetable oils and their derivatives in asphalt modification in terms of blending protocol, interaction mechanism, and performance are summarized and highlighted. This paper attempts to provide valuable guidance for the options of vegetable oil-based materials regarding the target performance of modified asphalt and may provide insights towards the design of new vegetable oil-based materials for use in asphalt. [ABSTRACT FROM AUTHOR]

Accurately predicting the rutting development law of asphalt pavement is of great significance for preventing and controlling pavement diseases. The aggregate skeleton of the asphalt mixture is the main load-bearing part and plays an important role in its anti-rutting performance. However, quantitative and mesoscopic evaluation indicators and standards for aggregate skeletons have not been established. This study aims to reveal the relationship between the mesostructured characteristics of asphalt mixtures and rutting damage. This paper uses two-dimensional image technology to analyze the dynamic change process of internal skeleton information of two graded asphalt mixtures under cyclic wheel load. According to the fractal theory, the fractal dimension and multifractal spectrum of the full-depth aggregate were calculated. The results indicate that the linear regression model between the mesoscopic skeleton information of asphalt mixture and the average rutting depth during the rutting test can be used to quantify the rutting performance. There is an obvious correlation between the fractal dimension of the section aggregate and the loading times, and there is a certain linear relationship between the multifractal spectrum indexes and the loading times. It indicates that the fractal theory index of aggregate can reflect the change of the macro performance of loading times. • The fractal and multifractal analysis of the section aggregate of the rutting test was carried out. • T The relationship between meso skeleton information and rutting depth is established. • The multifractal index of aggregate can reflect the change of macro performance after loading times. [ABSTRACT FROM AUTHOR]

The traditional method of crumb rubber modified asphalt (CRMA) preparation can improve the stability but is not conducive to cleaner production. From the perspective of process optimization, ultrasound is introduced into the crumb rubber modified asphalt preparation process, and the high temperature, high pressure and high energy accompanied by the cavitation effect are used to generate free radical triggering chemical effects at the two-phase interface between crumb rubber and asphalt. In this paper, the influence of ultrasound on the compatibility and stability of crumb rubber modified asphalt system was evaluated by combining experiment and molecular dynamics simulation. An experimental platform for ultrasound-assisted preparation of crumb rubber modified asphalt was established. The effects of ultrasonic on the physical properties of asphalt and crumb rubber modified asphalt were studied through Brookfield viscosity test, thin film oven aging test and Fourier infrared spectroscopy. The base, aged, and ultrasonically treated asphalt samples were simulated using molecular dynamics, and various parameters such as Cohesive Energy Density (CED), Mean Square Displacement (MSD), and Free Volume Fraction (FFV) of asphalt and its components were calculated and analyzed. The results showed that under the ultrasonic-assisted preparation, the agglomeration phenomenon of rubber particles is weakened, the particle size is reduced, the penetration degree is reduced, and the compatibility between rubber and asphalt is improved. Under the action of ultrasonic, the MSD and diffusion coefficient of crumb rubber modified asphalt are much higher than other kinds of asphalt, the dipole moment is increased, and the molecular motion range is wider. This indicates that the diffusion ability of crumb rubber modified asphalt is significantly enhanced under the external force of ultrasonic simulation. The molecular bonds of crumb rubber modified asphalt changes greatly, the energy decreases obviously, and the system stability increases. In conclusion, ultrasonic action on crumb rubber modified asphalt preparation is a green and effective way to improve system stability and compatibility. • The crumb rubber modified asphalt was prepared by ultrasonic method, which improved the compatibility and stability. • Perl script is used to simulate the sinusoidal force of ultrasonic field, and the molecular diffusion ability is enhanced. • Ultrasonic technology has a positive effect on preventing crumb rubber particle agglomeration during short-term aging. • An efficient production method of modified asphalt prepared by ultrasonic was proposed in the process innovation. [ABSTRACT FROM AUTHOR]

To prepare SBS modified asphalt (SMA) waterproofing membrane with excellent self-healing performance, in this paper, four self-healing agents (ASHA-A, ASHA-B, ASHA-C, ASHA-D) with acylhydrazone bonds and carbon-carbon double bonds (C C) were synthesized, and were used to prepare self-healing SMA waterproofing membranes (SSMA-A, SSMA-B, SSMA-C, SSMA-D). The effects of ASHAs with different structures on the structure, high and low temperature properties, joint peel strength and self-healing performance of SSMAs were investigated. The Fourier transform infrared spectroscopy and fluorescence microscope results showed that acylhydrazone bonds of ASHAs were introduced into the chains of SBS molecules, and the SBS in SSMAs occurred crosslinking through the C C of ASHAs and SBS, the crosslinked network structures of SBS in SSMA-C and SSMA-D were denser and more complete because ASHA-C and ASHA-D contained more C C involved in the crosslinking reaction. The softening point and low temperature flexibility of SSMAs were enhanced by the formation of the SBS crosslinked network structure, and the optimum dosage of ASHAs was 0.6%. The joint peel strength of SSMA-A, SSMA-B, SSMA-C and SSMA-D increased by 26.68%, 31.25%, 49.52% and 56.97% compared to SMA. The introduction of acylhydrazone bonds with reversible fracture and rearrangement significantly improved the crack self-healing performance of SMA, the impermeability times of SMA, SSMA-A, SSMA-B, SSMA-C and SSMA-D were 13.28 min, 37.29 min, 42.53 min, 53.34 min and 59.67 min after self-healing at 40℃ for 8 h, which indicated that ASHA-D with benzene ring and multiple C C had the best improvement in self-healing performance of SMA. [Display omitted] • Acylhydrazone self-healing agents with different structures were synthesized. • The introduction of acylhydrazone bonds improved the crack self-healing performance of SBS modified asphalt waterproofing membrane. • The effect of acylhydrazone self-healing agents on the properties of SBS modified asphalt waterproofing membrane was investigated. [ABSTRACT FROM AUTHOR]

This paper introduces a groundbreaking approach to enhance shear resistance in pavement structures through the utilization of crumb rubber modified asphalt gravel as an innovative bonding layer. The study addresses the challenge of interlaminar shear failure in semi-rigid base asphalt pavement by conducting 48 shear experiments with 144 samples. The optimization process involves varying parameters such as rubber powder mesh size, modified asphalt application amount, gravel particle size, and gravel application amount. ANOVA results underscore the significance of these factors, with gravel particle size, application rate, and rubber powder modified asphalt rate playing crucial roles. The optimal bonding layer configuration is identified as 40 mesh rubber powder, 0.9 L/m2 dosage, 80% gravel, and 5–10 mm gravel particle size. Comparative analysis demonstrates the superior shear strength of the rubber powder modified asphalt gravel bonding layer, achieving nearly twice the strength of base asphalt and three times that of emulsified asphalt. Numerical analysis affirms its robust performance under extreme driving loads, providing a maximum shear stress of 0.0826 MPa even at 100% overload, while the bonding layer can offer 1.148 MPa. Evaluation across low, medium, and high service temperatures reveals consistent superiority over traditional bonding materials. The study emphasizes the sustainable nature of this innovation, utilizing recycled scrap tires, reducing carbon emissions, and offering environmental and economic benefits. In conclusion, rubber powder-modified asphalt macadam bonding layers emerge as a promising solution for enhancing shear performance in pavement structures. • Effective Shear Resistance: Crumb rubber-modified asphalt gravel enhances pavement shear resistance. • Optimal Parameters: Ideal bonding layer: 40 mesh rubber, 0.9 L/m2 asphalt, 80% gravel, 5–10 mm size. • High Shear Strength: Comparative analysis shows superior shear strength over conventional layers. • Robust Performance: Finite element modeling confirms resilience under simulated driving loads. • Sustainable Solution: Recycling crumb rubber reduces emissions, offering environmental and economic benefits. [ABSTRACT FROM AUTHOR]

The current standard in China does not specify the standard test method for determining Poisson's ratio, and the Poisson's ratio used in pavement design is often roughly fixed, which can result in large errors in the calculations and analysis of road structure. In this paper, the research on different test methods for Poisson's ratio is carried out and the non-linear characteristics of tensile and compressive Poisson's ratio on pavement materials under different influencing factors are analyzed. The results indicate that the absolute value of the ratio between transverse rebound strain and longitudinal rebound strain under 50% of the maximum destructive load can objectively characterize the mechanical properties of Poisson's ratio, and it is the optimal measurement method for Poisson's ratio in asphalt pavement materials. The Poisson's ratio of two pavement materials both decreases with the increase of loading rate and gradually tends to a constant value. Cement dosage and temperature are the most significant factors affecting the tensile and compressive Poisson's ratio of cement stabilized crushed stone and asphalt mixture, respectively. Specifically, when cement dosage increases by 1%, the Poisson's ratio of cement stabilized crushed stone decreases by approximately 10%, and the temperature has a significant influence on the difference in tension and compression for Poisson's ratio of asphalt mixture (up to 40%). The asphalt content corresponding to the minimum Poisson's ratio is basically consistent with the optimal asphalt content obtained by the Marshall volume method. Based on these, a quantification value-taking model is established of the tensile and compressive Poisson's ratios of typical asphalt pavement materials varying with multiple factors. The research results can serve as a reference for the scientific value-taking of pavement structural design parameters considering the different mechanical characteristics of materials in tension and compression. • The scientific and reasonable measuring method of Poisson's ratio was established. • The quantitative model of Poisson's ratio affected by many factors was established. • The Poisson's ratio increases with loading speed and gradually tends to stabilize. • The optimum asphalt content mixture by Marshall method has minimum Poisson's ratio [ABSTRACT FROM AUTHOR]

This paper proposed an optimized fatigue life prediction model of graphene oxide (GO) modified asphalt binder considering the coupled effects of nonlinear viscoelasticity (NLVE) and intrinsic healing compensation. The equivalent nonlinear complex modulus (|G*| NLVE) was quantified accordingly and an NLVE-based fatigue model was proposed in this study. The parameters damage healing (Δ S '), local life compensation (Δ N), damage healing index (% H S), and local lifetime compensation index (%Δ N) were employed to characterize the intrinsic healing capability and mechanism of GO-modified binders. There is a strong correlation mechanism between the healing compensation effect and the damage healing of asphalt binders during healing intervals, as evidenced by the linear relationship between Δ S ' vs. Δ N and % H S vs. %Δ N. Furthermore, the analysis of the total stored pseudo-strain energy counteracting the damage healing reveals that GO-modified binder has greater stiffness and require more stored pseudo-strain energy to counteract Δ S '. The fatigue life of asphalt binder is further prolonged by the healing compensation effect on the basis of GO modification and NLVE effects. • A refined S-VECD model covering nonlinear viscoelastic effects and intrinsic healing behavior is proposed. • Emphasis is placed on the asphalt stiffness modulus evolution law under high level and discontinuous loading. • The inherent mechanisms behind fatigue life extension were discovered for damage healing. [ABSTRACT FROM AUTHOR]

In this paper, we introduce a novel material parameter termed the 'scalar modulus,' conceived through the expansion of the elastic-viscoelastic correspondence principle. The extended principle and associated transformations open new avenues for applying this framework under non-constant strain rate conditions, particularly in scenarios like creep test. Through a combination of rigorous experimental observations and numerical analysis, we establish a crucial relationship between the creep rate/creep compliance rate and the 'seed property' known as the scalar modulus. This relationship proves to be distinctive for diverse asphalt compositions, temperatures, and loading conditions, effectively delineating the material's internal states. To validate the versatility of this novel concept, we conducted an extensive series of experiments on various asphalt concrete mixtures with varying aggregate types, gradation, air void content, binder content, and aging durations. The experimental approaches to obtain the scalar modulus encompasses Superpave IDT tests, uniaxial static creep tests under tension and compression, as well as both destructive and non-destructive creep tests. By thoroughly examining the scalar modulus and characterizing the material behavior under varying composition and conditions, we gain crucial insights into its creep behavior and its reaction to external mechanical loads. •.A 'seed property' scalar modulus is introduced from the elastic-viscoelastic correspondence principle. • The correlation of creep rate to scalar modulus via simple static creep tests across different asphalt mixtures. • Insights into temperature, aging, and air void content affect scalar modulus and creep rate. • A novel predictive model for creep compliance rate is proposed and validated across diverse asphalt mixtures. [ABSTRACT FROM AUTHOR]

Common procedures to incorporate the recycled crumb rubber (CR) in asphalt binders take a long time and use a high-temperature heating process, which makes these rubberized mixtures even more expensive and environment-unfriendly than conventional mixtures. In trying to make a cheaper and greener asphalt mixture, in this paper, the CR incorporation heating process and its duration were lowered (140–150°C in 15 minutes), and the effect of these changes was studied on the pavement's tensile/shear cracking resistance. Because the main disadvantage of using CR is the increase of viscosity, two by-products, slack wax (SW) and polypropylene wax (PPW) were used to correct the viscosity; also their effect on fracture toughness (K eff) and fracture energy (G f) was assessed. As results showed that the following process decreases the cracking resistance, calcium carbonate nanoparticles (CCN) in different contents were added. Results show that adding 15% CR reduces K eff and G f by about 18 and 16%, respectively. Adding the SW and PPW further reduces them by about 8 and 16%, respectively. In this condition, adding CCN in optimal content (about 5%) compensates for these reductions. Although these greener asphalts have the same cracking resistance as the control mixture, the environmental and cost-effectiveness analysis shows the developed materials are greener and cheaper. [Display omitted] • The effect of addition of crumb rubber to neat binder was studied. • The mechanical tests were done for the aim of cracking resistance measurement. • The calcium carbonate nanoparticles and two wax-based additives was used to enhance the performance. • Full range of mode I and II fracture was studied, experimentally and theoretically. • Statistical review, optimization and cost-environmental evaluation were done. [ABSTRACT FROM AUTHOR]

The randomness and variation of material composition at the meso-scale lead to some limitations in the application of asphalt mixture. When all features are taken into account, the computational effort increases significantly. Therefore, the relationship can be established using the meso-element equivalence method (MEEM). In this paper, the effects of aggregate-asphalt interface, initial void defects and material damage were introduced and MEEM of asphalt mixture was established based on industrial computed tomography (ICT) and finite element method (FEM). The rationality of the model was verified by laboratory performance tests, and the effects of aggregate type, mixture gradation and mesostructural parameters on the mechanical response of MEEM were compared and analyzed. The results showed that the MEEM model captures the mechanical behavior of asphalt mixtures well, the input of visco-elastic material parameters is an important step of MEEM simulation accuracy. The aggregate type, the discrete degree of the skeleton structure and the distribution characteristics of mesostructural parameters are important factors affecting the mechanical properties of asphalt mixture in MEEM. • The model of the material homogenization of the asphalt mixture is realized by using the meso-unit equivalence method at the meso scale • The effects of the aggregate-asphalt interface, initial void defects, and material damage are introduced in the equivalence process • The validity of the meso-unit model is verified by digital image correlation based on indirect tensile test • Different factors on the mechanical response of asphalt mixtures in MEEM are compared at the meso scale. [ABSTRACT FROM AUTHOR]

In the actual service process of asphalt pavement, the dynamic response of the pavement structure layer is induced by vehicle loads. The dynamic modulus is a crucial parameter for analyzing the mechanical response of asphalt pavement. Due to significant influences from temperature and loading frequency on test measurements, along with its time-temperature equivalence, it becomes imperative to investigate the behavior of dynamic modulus under different temperature frequencies. Furthermore, laboratory loading modes also exert substantial effects on dynamic modulus. Employing different loading modes during measurement often leads to significantly varied stress states in specimens, yielding distinct values for dynamic modulus. Therefore, this study conducts dynamic modulus tests using direct tension, uniaxial compression, and indirect tension under five test temperatures and six loading frequencies while examining its variations under different stress states and temperature frequencies. The corresponding master curves and prediction models of dynamic modulus are derived, providing a valuable reference for predicting the dynamic modulus under wide-area test conditions. Through comparative analysis of dynamic modulus values at different stress levels, the stress level is incorporated into the master curve to establish corresponding master curves of dynamic modulus. By applying relevant theories and research on time-temperature equivalence, we obtained dynamic modulus master curves for three loading modes by fitting and analyzing dynamic modulus test data at various temperatures and loading frequencies. Combining the Sigmoid model and Williams-Landel-Ferry(WLF) equation, we derived prediction models for dynamic modulus under three loading modes. Comparative analysis of dynamic modulus values under these three loading modes allowed us to establish transformation equations for the prediction models in different loading scenarios. Finally, representative dynamic modulus values for permanent deformation in typical pavement structure layers were predicted based on laboratory test results and the derived models. The research findings presented in this paper have significant implications in eliminating the influence of loading modes on dynamic modulus predictions, establishing a unified prediction model, and providing essential parameters for predicting permanent deformation and fatigue life equivalent temperature. • Introducing stress level variables into the dynamic modulus master curve. • Extending the two-dimensional dynamic modulus master curve to three-dimensional master surface. • Derived the conversion equations between prediction models for different loading methods. [ABSTRACT FROM AUTHOR]

Although Fourier transform infrared spectroscopy has been widely used in research on the aging of asphalt binders, it is a cumbersome, time-consuming, and environmentally polluting process using toxic solvents to extract and recover asphalt binders from asphalt mixtures for spectral measurement and analysis. However, little effort has been devoted towards its non-destructive spectral measurement, which is important for intelligent monitoring of pavement deterioration conditions. This paper focused on the non-destructive investigation of comparative near-infrared spectra of asphalt mixture specimens designed using the Marshall method after laboratory short- and long-term aging with a portable near-infrared spectrometer. The near-infrared spectra showed that asphalt mixtures from different aging states appeared significantly different fingerprints. The near-infrared fingerprints and aging states were also statistically significantly different according to the analysis of one-way analysis of variance. These distinctive near-infrared fingerprints could be attributed to the varied amounts of chemical functional groups, mainly hydrogen-containing groups during oxidative aging. This study provided a non-destructive and in-situ detection of the aging of asphalt mixtures. • The portable NIR spectrometer is used for the measurement of asphalt mixtures. • Asphalt mixtures from four aging states have unique and distinct NIR fingerprints. • ANOVA indicates a statistical difference in NIR spectra from four aging states. • NIR spectroscopy is suitable for in-situ detection of aging of asphalt mixtures. [ABSTRACT FROM AUTHOR]

This paper summarizes the important research results of self-healing technology of asphalt materials, analyzes the healing mechanism of self-healing technology, and emphatically introduces the research status, advantages and disadvantages of five advanced self-healing technologies: Electromagnetic induction heating (EIH) technology, Microwave induction heating (MIH) technology, Photorepair method, Microcapsule method, and Hollow fiber (HF) method. The results showed that the existing self-healing mechanism is mainly based on surface energy theory, molecular diffusion theory and capillary flow theory, which explains the self-healing phenomenon of asphalt from different scales. The existing self-healing technology has developed rapidly, and the indoor research proves that the potential of MIH technology is higher than that of EIH technology. The repair potential of HF method is higher than that of microcapsule technology, but its material synthesis is more complicated. Photorepair technology has the potential to cooperate with other technologies, and it needs to be reasonably matched and selected. At the same time, the progress of related self-healing construction machinery and technology may require the continuous efforts of researchers. In addition, the organic synergy between different self-healing technologies may be a feasible way for self-healing technology to move from experimental section to practical application. In the future, a set of self-healing system with strong repair effect, environmental friendliness and reasonable cost can be established from the organic synergy of various self-healing technologies, combined with life cycle cost and intelligent sensors. • The existing mechanism explains the self-healing of asphalt from different angles. • The uneven heating of the induction heating technology still exists. • Photorepair method has the potential to combine with other technologies. • Relevant standards of self-healing technology need to be established. [ABSTRACT FROM AUTHOR]

The study of microscopic processes in modified asphalt is crucial for road engineering but has been challenged by difficulties and means limitations. The phase field model, on the other hand, can accurately simulate and track the evolution of the microscopic phase state of modified asphalt with respect to time, and by simulating the interactions and distribution of different asphalt components, we can predict the asphalt microscopic processes under different conditions. This paper reviews the application of phase field theory to microscopic phase separation, self-healing and fracture behavior of asphalt, and concludes with a brief summary and outlook on the current problems in the application of phase field theory to modified asphalt. • The phase field theory can accurately model and track the evolution of the microscopic phase state of modified bitumen over time, providing insight into the phase separation process. • Allen-Cahn kinetics and Navier-Stokes equations coupled with evolving phase field variables are used to simulate the self-healing process of asphalt. • The interactions and distribution of different components of asphalt are modeled by phase field theory to predict the fracture properties of asphalt under different conditions. [ABSTRACT FROM AUTHOR]

In this paper, the structural evolution of natural rock asphalt and rock asphalt treated with liquid nitrogen subjected to high temperature and high pressure (HTHP) were studied, and then its influence on mechanical properties of oil well cement was investigated. The results show that the pyrolysis reaction of rock asphalt was promoted by HTHP, which occurred at 320 ℃ at normal pressure and appeared at 180 ℃/20.7 MPa. The pores in the particles caused by the pyrolysis of rock asphalt were healed with the extension of curing time, and the interface bond between rock asphalt and cement matrix was improved. Rock asphalt has a good toughening effect on cement paste, especially treated rock asphalt. • High temperature and high pressure promoted the pyrolysis of rock asphalt. • The rock asphalt treated by liquid nitrogen can enhance the toughness of cement stone under HTHP. • The interface bond between rock asphalt and cement matrix was gradually improved with the extension of curing time. [ABSTRACT FROM AUTHOR]

This research paper presents the effects of electrophilic modification on raw nano clay (which is hydrophilic in nature) through wet impregnation method to transform it into hydrophobic nature. The reactivity, adsorption capability, and compatibility of nano clay with hydrocarbon and organic materials are improved by entailing functional group (QAS) on raw nano clay surface. Impact of impregnated organophilic nano clay (hydrophobic) on asphalt binder properties and mixture's performance are studied. Organophilic(hydrophobic) nano clay with 3–5% content to the weight of the binder were selected after extensive trials for modification of asphalt binder. To analyze the electrophilic changes in organophilic nano clay (ONC) and its bonding chemistry with asphalt binder, FTIR analysis, and X-ray diffraction techniques were utilized. In addition, viscosity, low & high-temperature stiffness, bitumen bond strength, and phase separation were studied in the lab. The effect of organophilic nano clay modified binder on asphalt mixture was also measured by deploying rut resistance, moisture susceptibility& fatigue resistance tests. The study revealed that raw nano clay showed chemical compatibility with asphalt binder after electrophilic modification through wet impregnation method. ONC modified binder had better rheological properties, homogenized composition, and storage stability than hydrophilic nature. Mixtures prepared with ONC showed better resistance to rutting, fatigue, and moisture susceptibility. • The organophilic nature of nanocaly after the impregnation treatment improves asphalt binder and mixture properties better than its hydrophilic. • The electrophilic alteration can be successful by the wet impregnation method as indicated in the FTIR spectrum. • The XRD pattern shows that insignificant volume enlargement has occurred in organophilic nano clay as indicated by the diffraction angle. • The organophilic nanoclay improves asphalt binder properties like rut resistance, brittleness, phase separation and adhesion. [ABSTRACT FROM AUTHOR]

To accurately evaluate the modification effect of direct-to-plant styrene–butadiene–styrene block copolymer (SBS) modifier on asphalt, a collection method for direct-to-plant SBS-modified asphalt was proposed in this paper, the qualitative and quantitative evaluation index system was established, and the feasibility of quantitative evaluation based on fluorescence microscopy images and visual inspection of the mixing effect was evaluated, the feasibility of quantitative evaluation indicators was also verified based on the asphalt indicators, rheological properties, and asphalt mixtures's pavement performances. The research results indicate that based on fluorescence microscopy images, by observing the distribution and swelling state of direct-to-plant SBS modifiers can qualitatively evaluate the modification effect of direct-to-plant SBS modifiers on asphalt. Based on the visual inspection of the mixing effect, observe the size and quantity of unmelted particles, determine the melting state of the direct-to-plant SBS modifier, and its modification effect on asphalt can be qualitatively evaluated. For the same direct-to-plant SBS-modified asphalt, the percentage of rotation viscosity between direct-to-plant SBS-modified asphalt and traditional SBS-modified asphalt at 135 ℃ (DA η (135 ℃)) and discrete coefficient of 135 ℃ rotational viscosity of direct-to-plant SBS-modified asphalt (CV η (135 ℃)) exhibit a linear relationship with direct-to-plant SBS-modified asphalt's penetration, softening point, and ductility, the smaller the CV η (135 ℃) , the greater the DA η (135 ℃). The smaller the CV η (135 ℃) (the larger the DA η (135 ℃)), the larger the dynamic shear modulus (G *), the smaller the phase angle (δ), and the larger the rutting factor ( G * / sin δ) at the same scanning temperature. The relationship between CV η (135 ℃) (DA η (135 ℃)) and direct-to-plant SBS modifier on the main technical indicators and rheological performance indicators of asphalt is relatively stable. There is a clear relationship between CV η (135 ℃) (DA η (135 ℃)) and the high-temperature stability, low-temperature crack resistance, and water stability of direct-to-plant SBS-modified asphalt mixture, all of which show that as CV η (135 ℃) decreases (DA η (135 ℃) increases), the pavement performances improve. • The collection method for direct-to-plant SBS-modified asphalt is proposed. • A qualitative evaluation method for the modification effect of direct-to-plant SBS modifier on asphalt is proposed. • The quantitative evaluation index for the modification effect of direct-to-plant SBS modifier on asphalt is proposed. [ABSTRACT FROM AUTHOR]

There is no direct, less expensive, and practical method to measure the interconnectivity and parameters of air voids in asphalt mixtures other than the total air void volume calculated traditionally using bulk and maximum theoretical specific gravities. Unlike the conventional method, this paper proposes a method that is suitable for advanced applications and studies, such as for the evaluation of air void distribution and air void gradient to model and simulate long-term aging, predict top-down fatigue cracking, evaluate the effectiveness of compaction of thick lifts, and satisfy the representative volume element (RVE) requirements (a homogenous and representative specimen) for performance tests. Developing the proposed compact asphalt evaluation method included modifying the sample preparation methods and analysis from the American Society of Testing & Materials (ASTM), C457 Method C, and recently applied in the analyses of two independent studies at the Federal Highway Administration (FHWA). The first study was focused on checking the air void distribution within the small specimen for dynamic modulus and uniaxial cyclic fatigue tests using AASHTO TP 132 and TP 133, respectively. Results of air void analyses conducted on the interior and exterior sides of several slices sawn from different compacted asphalt mixtures consistently showed that the air void contents on the external sides are higher than on the interior. The second study was to evaluate whether the thicker-than-typical lift thickness to nominal maximum aggregate (NMAS) ratio was causing any top-to-bottom air void gradient in the pavement. Results showed that air void sizes and contents are consistently higher along the top ends of all the cores, and the total air void contents measured using the new method on several specimens from the field were comparable with the indirectly calculated air void percent with up to ± 0.4 percent random error. Overall, the new method is practical to apply to larger-size samples and is a tool that both agencies and contractors can use for confirming in situ void uniformity. Its application can support innovations and improve performance in asphalt pavement construction. • A reliable sample preparation procedure was developed that is applicable to compacted asphalt mixtures. • Results of air void contents measured using the quantitative petrographic method were comparable with the AASHTO Methods. • The method also provides information on void sizes, abundance, distribution, and air void gradients in asphalt pavement. [ABSTRACT FROM AUTHOR]

Recycled aggregate (RA) is a product of construction and demolition wastes, and RA particle presents low strength and adhesion with asphalt mortar compared with natural aggregate. With the aim of studying fracture characteristics of recycled aggregate asphalt concrete (RAAC), the influence of RA on interfacial zone failure should be evaluated. In this paper, RAAC with different RA percentages and gradations were prepared, and a semi-circular bending test (SCB) was employed to assess the fracture behavior of RAAC specimens. Meanwhile, strain distributions during the fracture process were measured by digital image correlation (DIC). To understand the influence of RA on fracture characteristics of RAAC, the microstructural finite element models (FEM) were established, in which natural aggregate and RA particles were reconstructed, respectively. Zero-thickness cohesive zone elements (CZM) were inserted into continuum elements so that the failure of the interface zone between asphalt mortar with different aggregate particles could be investigated. Results indicate that RA presents a significant impact on the fracture response of the asphalt mixture, and the fracture resistance of RAAC attenuates significantly as the RA percentage exceeds 50%. The aggregate-asphalt mortar interface is the first choice in competing fracture paths inside RAAC. The cement mortar-asphalt mortar interface (CAI) exhibited more significant damage than the bulk fracture within the asphalt mortar (AMI) and natural aggregate-mortar interface (NAI). Also, the damage proportion of CMI increases with RA percentage and the maximum nominal particle size of RAAC. This study shows FEM considering different types of interfacial zone provides an effective method to evaluate the fracture characteristics of RAAC. • Low-temperature fracture performance of asphalt mixture containing recycled aggregates was investigated. • The influence of RA on interfacial damage in RAAC under low-temperature fracture was quantified. • The competition mechanism of crack initiation and developing paths inside RAAC was obtained. [ABSTRACT FROM AUTHOR]

Permanent deformation, fatigue and thermal cracking are the three typical distresses of flexible pavement. Using hydrated lime (HL) into the conventional limestone mineral additive has been widely practiced, including in Europe, to improve the mechanical properties of hot mix asphalt (HMA) concrete and as the result the durability of the constructed pavement. Large number of experimental studies have been reported to find the optimum addition of HL for the improvement on HMA concrete mechanical properties, moisture susceptibility and fatigue resistance. Pavement in service is under complex thermomechanical stress-strain conditions due to coupled atmospheric and surrounding environment temperature variation and the traffic loading. To predict and analyse the performance of pavement structures the data only from uniaxial compressive test for the resilient modulus and permanent deformation would be not enough. However, so far, the data of HL modified HMA concrete under complex loading conditions are still not well informatively complete. To contribute new knowledge, this paper reports an experimental study of both uni- and tri-axial tests for the asphalt concrete using HL into mineral additive for the mixes designed for the applications of wearing, levelling, and base layers, respectively. All the tests were conducted under three controlled temperatures and four stress deviations. The test results have showed that, for all three types of mixes, the permanent deformation of the HL mixes is less than the ones of no HL addition. The degree of the improvement on permanent deformation resistance using HL is much pronounced at high stress deviation states. The results have also showed that the resilient modulus strongly depends on the temperature and stress deviation while the mixes of HL addition demonstrate higher rigidity. At last, mathematical characterization models have been proposed for the measured material properties. A numerical simulation case study has been performed to test and demonstrate the application of the proposed unified property model. • Experimental work on uni- and tri-axial tests for asphalt concrete mixes using and without using the hydrated lime filler modification. • Novel mathematical characterization modelling on the experimental results for the resilient modules and permanent deformation. • Numerical case study simulation to demonstrate the application of the mathematical model proposed and developed in this work. [ABSTRACT FROM AUTHOR]

• Using paper-based asphalt felt (RPAF) as an asphalt-binder modifier. • Optimal parametric conditions for preparing, stirring and blending RPAF determined. • Parametric conditions assessed included stirring temperature, rate, and time. • Stirring rate was the most sensitive and influential parametric condition. • RPAF significantly improved the Penetration Index (PI) of virgin asphalt-binder. Utilizing reclaimed paper-based asphalt felt (RPAF) as a modifier does not only improve the engineering properties and performance of the corresponding modified asphalt-binder, but it also provides an alternative method for the environmentally friendly disposal of RPAF waste. However, there are currently no standardized preparatory procedures for the preprocessing and pretreatment of the RPAF additive to ensure a homogeneous blend and optimum performance for the resultant RPAF modified asphalt-binder. The work presented in this paper was directed at determining the optimal parametric criteria for harmonizing/standardizing the preparatory procedures, stirring, and blending conditions for using RPAF additives as an asphalt-binder modifier, namely the stirring temperature, stirring rate, and stirring time. A series of laboratory tests were conducted to assess and quantify the effects of these stirring conditions on the physical properties and storage stability of asphalt-binder modified with different RPAF dosages. For the materials evaluated, the Penetration, softening point temperature, and ductility test results indicated that the optimal parametric conditions to optimize the physical properties of the RPAF modified asphalt-binder were as follows: a stirring temperature range of 145 °C to 165 °C at a stirring rate of 5000 r/min to 5500 r/min for at least 30 min stirring time, with 5.0% being the optimum RPAF dosage. Overall, the study beneficially contributes to the literature enrichment through provision of a preliminary reference datum for the optimal parametric conditions of stirring, mixing, and blending RPAF when used as an asphalt-binder modifier. [ABSTRACT FROM AUTHOR]

• Bio-modification of Recycled Asphalt Shingles (RAS) could facilitate their application in pavement construction. • Bio-modification of RAS modified asphalt delays its physical hardening. • Bio-modification of RAS modified asphalt increases its crossover modulus and frequency. • Bio-modification of RAS modified asphalt increase its fracture energy and strain at failure. • Bio-modification of RAS modified asphalt increases its fatigue resistance. The use of recycled asphalt shingles (RAS) in pavement construction has received significant attention due to its economic and environmental advantages. However, asphalt binder in RAS is significantly aged and requires modification before application to ensure it does not compromise pavement performance. The paper introduces a novel approach to modify RAS to facilitate its application in new construction while examining the feasibility of rejuvenating RAS via bio-modification. In addition, this study investigates the durability of the modified RAS, referred to as bio-modified shingles (BMS), by exposing BMS to both severe oxidation aging and sub-zero extended conditioning followed by a comprehensive thermo-mechanical characterization. Study results showed the performance of RAS was significantly improved after bio-modification. The performance improvement was reflected in BMS having lower viscosities, stiffnesses, shear susceptibilities, crossover temperatures, while having higher m-values and failure strains compared to RAS asphalt. It was further observed that the enhancement lasted even after BMS was exposed to severe oxidation aging and 72 hr conditioning at −18 °C indicating an enhanced durability of BMS. The latter can be attributed to molecular interactions between the bio-modifier and aged asphalt disturbing the molecular packing of asphaltene and wax molecules. Such molecular packing is known as a dominant mechanism for hardening at sub-zero temperatures. This paper contributes to the body of knowledge and practice by providing insights on the merits of revitalizing recycled asphalt shingles to enhance its durability and facilitate its application in construction to promote sustainable construction practices. [ABSTRACT FROM AUTHOR]

Highlights • Mechanical characterization of fibers are described. • Papers of HMA reinforced with fibers were reviewed. • Fibers improve the viscoelastic behaviour of asphalt binder. • Fibers improve the mechanical performance of hot mix asphalt. • Fibers reinforce HMA through a tridimensional network and increasing adhesion in the mix. Abstract The use of fibers in hot mix asphalt (HMA) has become a much more attractive alternative for the construction of road pavements. Numerous studies have shown that the incorporation of fibers in the mixture improves fatigue resistance, permanent deformation and stiffness. The aim of this paper is to present a review of the mechanical impact of fibers in HMA by analyzing their reinforcement effect in a qualitative and quantitative manner. Fiber properties and characterization tests on fiber-modified bitumen are discussed. Quantities, blending procedures and performance of bituminous mixtures with different types of fibers are presented. Results of mechanical improvement are displayed. Based on the current research results, depending on the properties and the type of mixture in which they are used, each type of fiber seems to improve certain parameters more than others. Coconut fibers and waste fibers are described as environmentally friendly alternatives. [ABSTRACT FROM AUTHOR]

Highlights • A new stress sweep fatigue test for asphalt mixtures is proposed (called DUSST). • The new fatigue test is done in a shorter time than classical fatigue tests. • DUSST shows a good sensitivity of the main parameters evaluated. Abstract Fatigue cracking is one of the main damage mechanisms that take place in asphalt pavements. However, its evaluation during the design asphalt mixtures is not usually considered due to the complexity of the tests required, their high costs and the long time required to perform them. As a consequence, several research teams are working on developing new test procedures to reduce the time related to fatigue characterization of asphalt mixtures. In this context, this paper presents the development of a new test procedure consisting of a cyclic uniaxial tension-compression test in which the stress applied increases every 5000 cycles. In this manner, it is possible to evaluate a mixture's response under cyclic loading at different stress levels in one test. Also, failure of the mixture takes place in a shorter time period than that required by classical time sweep fatigue tests. This paper presents results obtained in the application of this new methodology to a mixture frequently used in Chilean pavement structures (type IV-A-12 by Chilean standards) with three different asphalt binders: a conventional binder (CA-24), a high modulus binder (CA-HM) and a polymer-modified binder (CA-PM). We evaluated three different types of aggregates obtained through two different shredding processes. Results achieved in the development of our Direct Uniaxial Stress Sweep Test (DUSST) show that it is an experimental method with great potential. This test can characterize fatigue behaviors of asphalt mixtures in a shorter time by using important parameters such as initial strain, failure strain, complex modulus and dissipated energy. In addition, we obtained a good sensitivity of the DUSST main parameters to variables evaluated. [ABSTRACT FROM AUTHOR]