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Salt erosion is an important negative factor on the performance deterioration of asphalt-based materials. The basic properties of asphalt in salt erosion environments have been extensively studied; however, there is a certain lack of research on the rheological property of styrene–butadiene–styrene (SBS) modified asphalt under various salt erosion conditions. This study aims to identify the rheology deterioration of SBS modified asphalt under the action of salt freeze–thaw or saline immersion cycles through laboratory experiments. Rheological properties and creep recovery properties of SBS modified asphalt were tested based on the dynamic shear rheometer, and their rutting resistance capacity and fatigue cracking resistance were analyzed. Viscoelastic properties and low-temperature property of SBS modified asphalt were investigated by Burgers model, Christensen–Anderson–Marasteanu model and glass transition temperature. Results showed that the rutting capacity increased by an average of 34.5% and 39.7% after 21 times salt freeze–thaw and saline immersion cycles, respectively, while the fatigue cracking resistance decreased by 34.2% and 40.1%. Multi-stress creep recovery test manifested that both salt erosion modes had slight influence on the creep recovery property. However, the non-recoverable creep compliance at 3.2 kPa decreased by 37.5% and 32.3% after 21 times salt freeze–thaw and saline immersion cycles, respectively. Based on glass transition temperature, the low-temperature performance of asphalt decreased significantly after salt erosion. The rheological behavior and damage degree of asphalt were different for different salt erosion modes. The study may provide a theoretical basis for the construction and maintenance of asphalt pavement in salt-rich areas. [ABSTRACT FROM AUTHOR]

The nondestructive testing of asphalt pavement using ground-penetrating radar (GPR) is based on studies on the dielectric properties of asphalt concrete. The equivalent circuit concept was used in this study, where different mediums are equivalent to a single multilayer medium. The capacitance of each layer medium was used to derive the composite dielectric constant. Using the open coaxial probe method, the dielectric constants of AC-13 and AC-16 concrete composed of No. 70, No. 90, and styrene-butadiene-styrene (SBS)–modified asphalt binder were measured. The results reveal that the dielectric constant of asphalt concrete falls as the binder-aggregate ratio increases, and the change in aggregate volume ratio is the most important element in determining its dielectric constant. For every 1% increase in the binder-aggregate ratio, the dielectric constant of asphalt concrete typically decreases by 0.094, while the volume ratio of asphalt binder increases by 1.39%. In addition, the volume ratios of aggregate and air decreased by 1.05% and 0.33%, respectively. When it comes to estimating the dielectric constant of asphalt concrete, the developed model outperforms the conventional dielectric model with an average relative error of roughly 1%. This model successfully improved the prediction accuracy of the dielectric properties of asphalt concrete materials, which is significant for GPR-based asphalt pavement quality assessment. [ABSTRACT FROM AUTHOR]

The balanced mix design (BMD) approach has emphasized the implementation of simple performance tests such as the indirect tensile asphalt cracking test (IDEAL-CT) and ideal rutting test (IDEAL-RT) for evaluating cracking and rutting performance of asphalt mixes for quality control (QC) and quality assurance (QA). The threshold values for CTIndex and RTIndex developed by many departments of transportation based on IDEAL-CT and IDEAL-RT tests, respectively, have proven to be useful for highway agencies. However, these limits are applicable only when tested using 150-mm-diameter samples. In many countries, Marshall mix design using 100-mm samples is quite prevalent and also similar diameter field core and lab compacted samples are used for various testing purposes. Therefore, the CTIndex and RTIndex threshold criteria developed based on 150-mm-diameter samples are not directly applicable to 100-mm-diameter samples. Therefore, the present study aimed to develop threshold values of CTIndex and RTIndex for 100-mm-diameter samples for practical application. Nine plant-produced dense-grade asphalt mixtures with different aggregate sizes and binder types were collected from various highway projects. The IDEAL-CT test at 25°C and IDEAL-RT test at 50°C were conducted on 150-mm and 100-mm-diameter samples. The proposed threshold limits for 100-mm-diameter samples were 50 and 110 for CTIndex and RTIndex , respectively, which were significantly different than used for 150-mm-diameter samples. Furthermore, the performance space diagram (PSD) developed based on limiting threshold value of CTIndex and RTIndex further highlighted the importance of the selection of appropriate acceptance criteria. [ABSTRACT FROM AUTHOR]

Copyright of Transportation Science & Technolgy is the property of Transportation Science & Technology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Colored asphalt pavements have been implemented in South Korea to enhance visibility and lane distinction; however, color fading, accelerated deterioration, and increased pothole occurrence have been noticed. As a solution, alternative materials that can be used for the construction of colored asphalt pavements are being explored. This study evaluates the feasibility of using mudstone aggregate in constructing colored asphalt pavement in South Korea. Initially, aggregate quality tests were conducted on mudstone samples to assess their suitability compared to standard criteria. To enhance the visibility and color retention of colored asphalt, addition of pigment in the colored asphalt pavement mixture was considered and evaluated. The asphalt mixtures were evaluated for deformation, crack and viscoelastic properties using the Kim test, indirect tensile (IDT) strength test, and dynamic modulus test, respectively. Results showed that mudstone aggregate exceeded quality standards and the colored asphalt mixtures demonstrated superior deformation strength and crack resistance compared to typical SMA. However, the addition of pigment slightly reduced these properties. Overall, the findings suggest mudstone aggregate as a viable alternative for constructing colored asphalt pavements, offering potential improvements in durability and color retention. [ABSTRACT FROM AUTHOR]

In order to solve the problems in predicting the asphalt aging behavior, such as the large performance deviation between simulated aging asphalt and actual aging asphalt, the lack of scientific evaluation index easy to promote in the practical engineering, properties of natural aging SBS (Styrene Butadiene Styrene Triblock Copolymer) modified asphalt from an in-service expressway were tested by Asphalt Binder Quality Test System (ABQT) . Then, some indexes, including maximum creep deformation, elastic recovery rate, loading deformation rate coefficient and rebound deformation rate coefficient, were proposed to evaluate the changes of asphalt’s properties; meanwhile, the accuracy of evaluating asphalt aging behavior with the above indicators were also analyzed by analyzing the differences between the above indicators and conventional performance indicators in evaluating the asphalt aging properties. On this basis, the nonlinear prediction model for asphalt aging was established based on the above indicators, and the aging rate values of asphalt were obtained to analyze the degradation laws of asphalt properties under natural aging conditions, and ultimately a reasonable preventive maintenance time was proposed. Results showed that, the maximum creep deformation, loading deformation rate coefficient and rebound deformation rate coefficient can effectively characterize the decay process of asphalt aging properties under natural aging conditions. Meanwhile, the nonlinear prediction model for asphalt aging established based on the above indicators had strong applicability, which can achieve bidirectional calculation for asphalt performance and aging time. Furthermore, as the aging time prolonged, the aging rate values corresponding to the maximum creep deformation, loading deformation rate coefficient and rebound deformation rate coefficient all decayed in the form of a cubic function model； and the turning points of aging rate were 6. 67 a, 5. 56 a, and 6. 67 a, respectively. Therefore, considering the safety of asphalt mixture performance, it was suggested that 5. 56 a as the threshold for intervention in preventive maintenance measures to restore asphalt performance. [ABSTRACT FROM AUTHOR]

Compound modified asphalt with waste plastic and crumb rubber can enhance the application of crumb rubber–modified asphalt (CRMA) in engineering, and enable the recycling of waste resources. In this study, waste cooking oil (WCO) was used to activate crumb rubber and acrylonitrile-butadiene-styrene (ABS) to obtain crumb rubber–modified asphalt with excellent storage stability and low viscosity. The viscosity and storage stability of crumb rubber–modified asphalt were tested by rotational viscosity test and cigar tube test. The force ductility test and bending beam rheological (BBR) test were used to evaluate the low-temperature performance of different crumb rubber–modified asphalt samples. The effect of the addition of waste cooking oil and acrylonitrile-butadiene-styrene on the low-temperature performance of crumb rubber–modified asphalt was explored by using the Burgers model fitting parameters and the ΔTc value between the limit temperature of the critical low-temperature performance grade. The test results showed that cooking oil reduces the rotational viscosity of crumb rubber–modified asphalt, and acrylonitrile-butadiene-styrene enhances its storage stability. When the acrylonitrile-butadiene-styrene and waste cooking oil contents reached 4% and 3%, respectively, the rotational viscosity and separation index values of crumb rubber–modified asphalt decreased by 11.2% and 49.8%, respectively. Waste cooking oil notably enhanced the crumb rubber–modified asphalt's ductility, particularly in the case of crumb rubber–modified asphalt compounded with 4% acrylonitrile-butadiene-styrene and 3% waste cooking oil, exhibiting the longest ductility and the highest toughness value, which were 85% and 75.6% higher than the original crumb rubber–modified asphalt, respectively. Insights from Burgers model parameters and ΔTc values revealed that waste cooking oil improves CRMA's stress relaxation ability and reduces its critical low temperature, and acrylonitrile-butadiene-styrene has no adverse impact on CRMA's resistance to low-temperature thermal cracking. Fourier transform infrared spectroscopy (FTIR) test results demonstrated that the addition of acrylonitrile-butadiene-styrene does not lead to a chemical reaction with crumb rubber–modified asphalt. [ABSTRACT FROM AUTHOR]

Cracks in asphalt mixtures compromise the structural integrity of roads, increase maintenance costs, and shorten pavement lifespan. These cracks allow for water infiltration, accelerating pavement deterioration and jeopardizing vehicle safety. This research aims to evaluate the impact of synthetic fibers, specifically glass fiber (GF) and polypropylene fiber (PPF), on the crack resistance of Hot-Mix Asphalt (HMA). An optimal asphalt binder content of 5% was used in all sample designs. Using the dry mixing technique, GFs and PPFs were incorporated into the HMA at dosages of 0.50%, 1.00%, and 1.50% by weight of the aggregate. The effects of these fibers on the mechanical fracture properties of the HMA were assessed using Semi-Circular Bending (SCB), Indirect Tensile Asphalt Cracking Tests (IDEAL-CTs), and Three-Point Bending (3-PB) tests. This study focused on fracture parameters such as fracture work, peak load, fracture energy, and crack indices, including the Flexibility Index (FI) and Crack Resistance Index (CRI). The results from the SCB and IDEAL-CT tests showed that increasing GF content from 0.5% to 1.5% significantly enhances the flexibility and crack resistance of HMA, with FI, CRI, and CT Index values increasing by 247.5%, 55%, and 101.35%, respectively. Conversely, increasing PPF content increases the mixture's stiffness and reduces its crack resistance. The PP-1 mixture exhibited higher FI and CT Index values, with increases of 31.1% and 10%, respectively, compared to the PP-0.5 mixture, based on SCB and IDEAL-CT test results. The SCB, IDEAL-CT, and 3-PB test results concluded that fibers significantly influence the fracture properties of bituminous mixtures, with a 1% reinforcement dosage of both PPFs and GFs being optimal for enhancing performance across various applications. [ABSTRACT FROM AUTHOR]

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

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

The development of tests, standards, and specifications necessitates the establishment of technical validity while concurrently optimizing costs associated with the testing requirements. AASHTO TP 125-16 recommends the utilization of the bending beam rheometer (BBR) as a simple, rapid, relatively cost-effective, and reproducible method for assessing the low-temperature properties of asphalt concrete mixtures. However, the standard does not provide specific guidance regarding the representative sample size necessary for the BBR test. Therefore, this study used statistical techniques to calculate the sample size by scrutinizing data for two variables, i.e., creep moduli (stiffness) and stress relaxation capacity (m -value), which were obtained from testing a variety of asphalt concrete mixtures. In this regard, distinct asphalt mixtures were meticulously prepared and subjected to laboratory testing. A representative sample size of eight thin-beam specimens was determined. This recommendation was validated by sampling five different asphalt mixtures from pavement construction projects. It was found that testing and analyzing trimmed means of only eight specimens from a 2 in. thick asphalt concrete layer was adequate to represent the global low-temperature performance of those five pavement sections. So, an asphalt mixture's low-temperature performance can be completed in 2 h by testing only eight specimens in the BBR without sacrificing accuracy and practicality. Therefore, this study contributes to a possible application of the BBR during pavement construction. [ABSTRACT FROM AUTHOR]

To analyze the long-term water stability of hydraulic asphalt concrete, the bending test, splitting test, and uniaxial compression test of asphalt concrete immersed at 20°C, 40°C, 60°C, and 80°C for different durations were conducted, and attenuation models for the bending strain, splitting tensile strength, and compressive strength of asphalt concrete under long-term immersion conditions were established based on the time–temperature equivalence principle. The results show that, at different temperatures, the bending strain, splitting tensile strength, and compressive strength of asphalt concrete decreased with the increase of water immersion time. The bending strain, splitting tensile strength, and compressive strength stabilized under long-term immersion at 80°C. The water stability of asphalt concrete during immersion can be analyzed quantitatively using the attenuation models and water stability coefficient. The water stability of hydraulic asphalt concrete tends to be constant under long-term immersion conditions. The sensitivity of the asphalt concrete performance indicators for water damage is in the order bending strain > splitting tensile strength > compressive strength. The long-term water stability of hydraulic asphalt concrete should be comprehensively analyzed by calculating the water stability coefficient using compressive strength, splitting tensile strength, and bending strain. The research results can provide new ideas for the quantitative analysis of long-term water stability of hydraulic asphalt concrete. [ABSTRACT FROM AUTHOR]

The dynamic modulus of in-service asphalt pavements serves as a critical parameter for the computation of residual life and the design of overlays. However, its acquisition is currently limited to laboratory dynamic modulus testing using a limited number of core samples, necessitating a reassessment of its representativeness. To facilitate the prediction of dynamic modulus design parameters through Falling Weight Deflectometer (FWD) back-calculated modulus data, an integrated approach encompassing FWD testing, modulus back-calculation, core sample dynamic modulus testing, and asphalt DSR testing was employed to concurrently acquire dynamic modulus at identical locations under varying temperatures and frequencies. Dynamic modulus prediction models for in-service asphalt pavements were developed utilizing fundamental model deduction and gene expression programming (GEP) techniques. The findings indicate that GEP exhibits superior efficacy in the development of dynamic modulus prediction models. The dynamic modulus prediction model developed can enhance both the precision and representativeness of asphalt pavement's dynamic modulus design parameters, as well as refine the accuracy of residual life estimations for in-service asphalt pavements. Concurrently, the modulus derived from FWD back-calculation can be transmuted into the dynamic modulus adhering to a uniform standard criterion, facilitating the identification of problematic segments within the asphalt structural layer. This is of paramount importance for the maintenance or reconstruction of in-service asphalt pavements. [ABSTRACT FROM AUTHOR]

Experts have given much attention on the use of waste in asphalt paving because of its significance from a sustainability perspective. This paper evaluated the performance properties of asphalt concrete mixes modified with Crumb Rubber (CR) as a partial replacement for two grade sizes of fine aggregate (2.36, and 0.3 mm) at six replacement rates: 0%, 2%, 4%, 6%, 8%, and 10% by weight. Asphalt concrete mixes were prepared at their Optimum Asphalt Content (OAC) and then tested for their engineering properties. Marshall properties, fatigue, rutting, ideal CT index test, Scanning Electron Microscopy (SEM), and Energy-Dispersive X-ray (EDX) spectroscopy were deployed to examine the crystalline structure and elemental composition of the CR-modified and unmodified asphalt concrete mixtures. The results showed a difference in Marshall's characteristics. The CT index revealed that the optimum cracking tolerance was achieved with a 2% CR substitution. Wheel track test results indicated that a 4% CR addition improved the rutting resistance of the asphalt mixture. SEM and EDX analyses exhibited significant changes in microstructure and elemental composition with the addition of CR. The main findings reveal that the use of 2% CR as a partial replacement of fine aggregate contributes to the production of more durable asphalt concrete mixtures with better serviceability. However, these results are based on laboratory experiments and require field verification to ensure practical applicability and long-term performance. [ABSTRACT FROM AUTHOR]

With the extensive application of coal gasification technology, the production and storage of coal gasification slag continue to increase. Expanding the application scope of coal gasification slag is of positive significance for mitigating environmental pollution. Coal gasification slag has potential in the field of microwave-heated asphalt mixtures; however, there is limited research in this area. This study attempts to investigate the impact of utilizing coal gasification slags as fillers on the self-healing properties of asphalt mixtures. For this purpose, two different types of coal gasification slag in five ratios (within the range of <0.075 mm , 10%, 20%, 30%, 40%, and 50%) were used to replace limestone filler (LF) for preparing the Marshall test samples. Firstly, the micromorphology, chemical composition, and microwave absorption properties of LF, coarse slag (CS), and fine slag (FS) were characterized by scanning electron microscopy, X-ray fluorescence tests, and electromagnetic measurement. Afterward, an infrared camera examined the microwave-heating behaviors of different asphalt mixtures under microwave irradiation. Furthermore, semicircular bending fracture–healing–fracture tests were carried out to evaluate the self-healing properties of the asphalt test samples. Finally, the economical aspects were calculated by the cost analysis. Results indicated that CS and FS exhibited excellent microwave absorption performance. However, the excessive use of CS or FS could potentially weaken the thermal diffusion behavior of asphalt mixtures. Moreover, the microwave-heating capacity and self-healing properties of asphalt mixtures containing coal gasification slag were improved compared to typical specimens. It was possible to find that 50% CS or 40% FS could be considered as the suitable alternative because this rate obtained excellent microwave-heating efficiency, while significantly increasing the self-healing ratio. Moreover, the statistical results demonstrated significant differences in microwave-heating capacity and self-healing properties between CS and FS asphalt mixtures. And the results of cost analysis showed that the utilization process can lead to substantial economic advantages. In general, this study proves the feasibility of utilizing coal gasification slag as a microwave absorber to accelerate the efficiency of microwave healing of asphalt mixture. This finding provides a new methodology for consuming coal gasification slag, enabling the reuse of waste resources. [ABSTRACT FROM AUTHOR]

High-precision 3D point cloud data have various analyses and application use cases. This study aimed to achieve a more precise noise reduction of the raw 3D point cloud data of asphalt pavements obtained using 3D laser scanning. Hence, a noise-reduction algorithm integrating improved Gaussian filtering and coefficient of variation was developed. A portable laser scanner was used to collect raw, high-precision 3D point cloud data of surface textures from pavement slab samples prepared with three different types of asphalt mixtures: AC-13, SMA-13, and OGFC-13, as well as asphalt from the test sections of the Yakang Expressway. An improved Gaussian filtering and Gaussian filtering that extracts noise using the coefficient of variation were used to filter out the obvious outlier noise and small-scale burr noise, respectively. Finally, the filtering effect of the proposed algorithm, Gaussian filtering, median filtering, and mean filtering on raw 3D point cloud data of pavement textures was evaluated through subjective visual quality and objective index evaluations. The results showed that the proposed algorithm filters out noise while preserving the micro-texture structure information, outperforming Gaussian filtering, median filtering, and mean filtering. [ABSTRACT FROM AUTHOR]

The aim of this paper is to investigate the adhesion of municipal solid waste incinerator bottom ash (MSWIBA) and limestone to asphalt using the principles of surface energy theory. MSWIBA asphalt mixes are known for their satisfactory water stability, with adhesion being a crucial factor, as demonstrated in previous freeze-thaw splitting tests. Contact angles of ground MSWIBA and limestone were measured using a capillary rise test, eliminating the influence of material surface structure. Subsequently, adhesion work and spalling work were calculated to correlate with water-induced damage. The results showed that the sequence of adhesion work was fine MSWIBA > limestone > coarse MSWIBA, while the sequence of spalling work was coarse MSWIBA > limestone > fine MSWIBA. The adhesion of MSWIBA asphalt mixes was evaluated using the water boiling test image method to validate the findings of surface energy theory. In both asphalt tests, the spalling rate followed this sequence: coarse MSWIBA > limestone > fine MSWIBA. The Adhesion index ER ranked as follows: ER Fine MSWIBA > ER limestone > ER coarse MSWIBA. These results suggest that the water stability of MSWIBA asphalt mixes is influenced by the surface energy of the components. Consequently, indices derived from surface energy theory can be applied in formulating and predicting the properties of MSWIBA asphalt mixes. [ABSTRACT FROM AUTHOR]

This paper evaluates the strength performance of hot mix asphalt produced with High Density Polyethylene (HDPE)-modified bitumen and Reclaimed Asphalt Pavement (RAP) which is partially replacing virgin aggregates. Asphalt Institute blending chart was used to determine the quantity of Reclaimed Asphalt Pavement (RAP) incorporated into the mixture. Thermo-gravimetric Analysis and Differential Thermal Analysis (TGA/DTA) were used to determine thermal stability of the High Density Polyethylene (HDPE). Fourier Transform Infrared (FTIR) was used for characterization of the HDPE, bitumen and modified bitumen. Physical test conducted on the RAP and virgin aggregates in accordance with American Society of Testing Materials (ASTM) standards revealed that the aggregates are adequate for use in asphalt production. Marshall method of mix design was adopted for the hot mix asphalt production and testing. With respect to the threshold, the results of Marshall stability showed a 6% increase in the strength of the asphaltic mixture modified with 10% High Density Polyethylene (HDPE). Other Marshall properties tested also showed improvements. Scanning Electron Microscopy and Energy Dispersive X-ray Spectrometry (SEM/EDS) were used for micro-structural examination and composing elements analysis of the asphaltic mixture, respectively. Fibermetric analysis was used to explore the fiber content and pores within the mixture. [ABSTRACT FROM AUTHOR]

The properties of asphalt mastic are crucial in determining the moisture sensitivity of asphalt mixtures, but the adhesion performance of the mastic has not been quantitatively described. To address this gap, this study calculated the asphalt mastic surface energy using the equation-of-state method, and established a moisture sensitivity (MS) index based on it. The effectiveness of this index was verified through Marshall testing. First, the surface energy of asphalt and filler was measured, and the critical volume fraction of the mastic was determined using the two-point method. Second, the interaction parameters of asphalt and filler were calculated using the equation-of-state method, and the surface energy of the mastic was obtained. Then the MS index was established to evaluate the moisture sensitivity of asphalt mixtures. This new index utilizes the surface energy and aggregate to quantitatively evaluate adhesion, considering the specific surface area of the aggregate and the thickness of asphalt film. Finally, the MS was validated through Marshall tests of asphalt mixtures. The results demonstrated that the MS obtained by the calculated surface energy exhibits a strong linear correlation with the moisture sensitivity of asphalt mixtures. The goodness of fit reached above 0.90 and the highest was 0.965. This study provided a novel approach to characterize the moisture sensitivity of asphalt mixtures. [ABSTRACT FROM AUTHOR]

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

Asphalt mixtures are widely used as a surfacing material for pavements due to their several advantages. For this reason, robust numerical models still need to be developed to improve the understanding of their fracture behaviour. Recently, an incremental generalised Kelvin (GK) contact model that relates increments in contact displacements with increments in contact forces was proposed to assess the viscoelastic behaviour of asphalt mixtures within a discrete element method (DEM) framework. In this work, the contact model is extended to allow its application to asphalt mixture fracture studies. Two damage models—a brittle and a bilinear softening—coupled with the GK contact model are proposed to consider damage initiation and propagation. A parametric study is presented that assesses the impact of the GK-Damage parameters, showing a sensitivity to the loading velocity and the Maxwell elements, particularly its viscosity element, on the stress–strain response of a single contact. A reduced-size numerical mastic is initially used to speed up the calibration process of the GK-Damage contact parameters, with subsequent validation on a specimen with real experimental dimensions. It is shown that the proposed calibrated damage models can successfully reproduce the time-dependent behaviour, peak stress, and crack path observed in experimental results, highlighting the benefits of the adopted methodology. For the GK-Bilinear model, the fracture energy and maximum contact tensile stress are shown to adjust both the peak stress and softening response. Uniaxial tensile tests on asphalt mixtures indicate that the GK-Bilinear model provides a more realistic characterisation of fracture development. A higher susceptibility to damage at aggregate-to-mastic contacts compared to contacts within the mastic phase is identified. [ABSTRACT FROM AUTHOR]

Weaknesses generated in asphalt pavement structures have a serious impact on the service life of pavements. In order to improve such situations and achieve the goal of enhancing the durability of the pavement structure, this study assesses the performance of heavy-duty asphalt and high-viscosity asphalt, using four high-performance asphalt mixtures: heavy-duty AC-20, high-viscosity AC-20, heavy-duty SMA-13, and heavy-duty SMA-10. Three composite pavement structures were designed: 3 cm SMA-10 + 3 cm SMA-10, 4 cm SMA-13 + 4 cm SMA-10, and 6 cm SMA-13 + 4 cm AC-20. Interlayer performance analysis was conducted on single-layer and composite structures through oblique shear tests; dynamic modulus, fatigue life, and antirutting performance tests on asphalt pavement structural layers were designed and conducted, and the durability performance of high-performance asphalt pavement structural layers was evaluated. The experimental results show that the shear strength of heavy-duty AC is higher than that of heavy-duty SMA, the 4 + 4 combination structure has the best shear strength, the 6 + 4 combination structure has the best structural performance and fatigue resistance, and the 3 + 3 combination structure has the best high-temperature antirutting performance. The comprehensive performance of the 4 + 4 structure is the best among the three combined structures, followed by that of the 6 + 4 structure, and the performance of the 3 + 3 structure is the worst. In addition, this study used bonding energy as an evaluation index and verified the applicability of the bonding energy evaluation index by studying four types of single-layer pavement structures and three types of composite pavement structures. [ABSTRACT FROM AUTHOR]

Copyright of Tikrit Journal of Engineering Sciences is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The fuel leakage of fuel vehicles will exacerbate the occurrence of distresses on asphalt pavements, including peeling, chipping and potholes, especially under the synergistic effect of traffic load and environment. In this research, Sasobit, which is commonly used as a warm agent in asphalt, is selected as the anti-fuel erosion agent and incorporated into SBS-modified asphalt and its mixtures. Diesel and gasoline are selected as the fuel erosion media. Sasobit/SBS-modified asphalt binder and its mixtures are investigated for fuel erosion. The rheological properties of bitumen and the mechanical properties of asphalt mixtures are assessed. The experimental findings show that the dissolution velocity of SBS-modified asphalt with 3% Sasobit is 0.2%/min for diesel erosion, while it is 1.7%/min for gasoline erosion, lower than the control sample without Sasobit. Meanwhile, the rutting factor of Sasobit/SBS-modified asphalt decreases less than that of the control sample without Sasobit. Furthermore, the mass loss ratio after the Cantabro test of Sasobit/SBS-modified asphalt mixtures is 1.2% for diesel erosion, while it is 6.8% for gasoline erosion, lower than that of the control sample without Sasobit. The results of the mechanical properties for asphalt mixtures demonstrate that Sasobit can enhance the anti-fuel erosion performance. Moreover, the research results of the Sasobit modification mechanism show that Sasobit can form a microcrystalline structure in SBS-modified asphalt, which subsequently improves the anti-fuel of asphalt and its mixtures. This research provides a reference for anti-fuel erosion assessment methods and solutions to improve the anti-fuel erosion of asphalt pavement. [ABSTRACT FROM AUTHOR]

Two-dimensional digital image correlation (2D-DIC) is a widely used optical technique to measure displacement and strain during asphalt concrete (AC) testing. An accurate 2D-DIC measurement can only be achieved when the camera's principal axis is perpendicular to the planar specimen surface. However, this requirement may not be met during testing due to device constraints. This paper proposes a simple and reliable method to correct errors induced by nonperpendicularity. The method is based on image feature matching with scale-invariant feature transform (SIFT) and rectification. No additional equipment is needed. A theoretical error analysis was conducted to quantify the effect of a nonperpendicular camera alignment on measurement accuracy. The proposed method was validated numerically using synthetic images and experimentally in an AC fracture test. It achieved relatively high accuracy, even under considerable camera rotation angles and large deformation. As a preprocessing technique, the proposed method showed promising performance in assisting the recently developed CrackPropNet for automated crack propagation measurement under a nonperpendicular camera alignment. [ABSTRACT FROM AUTHOR]

It is commonly known that mineral fillers significantly affect the asphalt mixture's performance. Superior flexible pavement performance can be ensured by gaining a deeper understanding of the function of filler. This research investigates the influence of three different fillers: granite dust, cement, and hydrated lime, at Australian asphalt mixtures. The testing program includes Marshall testing, moisture damage resistance, indirect tensile strength (ITS), and indirect tensile stiffness modulus (ITSM) tests of asphalt mixtures. Analysis of variance (ANOVA) was used to statistically assess the results obtained, besides damage analysis. The results indicate that using natural granite dust yields the highest resistance to moisture, while cement produces the highest stability, ITS, and ITSM. Unexpectedly, using hydrated lime filler decreases the stability/stiffness and moisture resistance of asphalt mixtures. ANOVA tests indicate that the type of filler affects ITS, TSR, and ITSM results (i.e., the p-value <0.05). The damage analysis shows that the design life of the asphalt mixture made with cement filler is higher than that of mixtures made with natural granite dust and hydrated lime fillers respectively. The findings indicate the important role of nontraditional fillers at the performance of Australian asphalt mixtures. [ABSTRACT FROM AUTHOR]

Thermal cracking significantly impacts the structural integrity of flexible pavements, particularly in colder regions like Canada. Limited studies investigated the impact of plastic modification of asphalt binders and mixtures using the wet method on the low-temperature performance of asphalt materials. The plastic material utilized in this project is multilayer plastic packaging (MPP). This study aims to determine whether MPP can be integrated to enhance the performance of the MPP-modified binder and MPP-modified mixtures, especially considering that MPP accounts for just over 40% of total plastic usage, making it the largest end-use market segment. This research evaluates the impact on rheological and mechanical behaviour when introducing MPP additives to conventional hot mix asphalt. This study used the wet method to test MPP-modified asphalt materials at 2%, 4%, and 8% (by weight of the asphalt binder). Test results demonstrate that the MPP modification percentage should ideally not exceed 2% as blends with 4% MPP or higher exhibited lower performance at low temperatures. The use of a softer binder as a base binder would help increase the MPP modification rates, but this hypothesis needs to be validated experimentally. [ABSTRACT FROM AUTHOR]

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

The impact of induction heating on the self-healing of asphalt mixture test specimens prepared with scrap metal and styrene–butadiene–styrene (SBS) modified bitumen was investigated in this study. In addition, the effects of waste metals used instead of aggregates in asphalt mixtures on the asphalt mixtures' mechanical properties were determined. To this end, asphalt mixtures were prepared to use two different percentages (inst aggregates of 50% and 100% aggregates) of waste metal in two different mill scale (cold mill scale and hot mill scale) and SBS in two different percentages (2% and 3%) to create prismatic and Marshall asphalt test specimens. Induction heating systems were used to determine self-healing properties. The samples were heated in five different heating times as 120 s, 100 s, 80 s, 60 s, and 40 s. To measure the performance of the recovery processing, five recovery cycles were performed for every asphalt sample. According to the results, the hardness of the mixtures, the mixes' fatigue life and load repetitions both shorten as the waste metal usage ratio in the asphalt mixtures increases. As both the amount of sludge and the amount of SBS in the asphalt mixtures increase, the maximum temperatures of the asphalt mixtures also increase. When the SBS ratio in the asphalt mixtures increases, the recovery rates increase. In addition, as the waste metal content in the asphalt mixture increases, an increase in HL values is observed. Finally, the general binding and rheological properties of SBS modified binders were evaluated. [ABSTRACT FROM AUTHOR]

As an agricultural waste, a large amount of corn stalk will cause environmental pollution. In order to realize the resource utilization of waste and meet the strict requirements of modern traffic on pavement strength and durability, it was modified and applied to an AC-13 asphalt mixture to study its influence on the road performance of asphalt mixture and its mechanism. The road performances of modified corn stalk fiber, lignin fiber, and ordinary asphalt mixtures were evaluated via the wheel tracking test, low-temperature bending test, water immersion Marshall test, freeze–thaw splitting test, and fatigue test. Based on the results of three-point bending fatigue test, the viscoelastic parameters and indexes of the fiber asphalt mixture were obtained by fitting the loading specimen and deflection data with the Burgers constitutive model, and the creep strain response was analyzed by applying dynamic load, so as to explore the relationship between the viscoelastic characteristics and creep behavior of modified corn stalk fiber and AC-13 mixture. The long-term high-temperature performance test of the asphalt mixture with the best fiber content was carried out by using the long-term pavement intelligent monitoring equipment independently developed by the group of investigators. According to the findings, the ideal fiber contents for modified corn and lignin in asphalt mixture are 0.2% and 0.3%, respectively. Among them, the modified corn stalk fiber with a 0.2% content has the best effect on road performance, viscoelastic performance, and the asphalt mixture's creep behavior under dynamic load. Compared with the 0.3% lignin fiber asphalt mixture, its dynamic stability, bending stiffness modulus, immersion residual stability, freeze–thaw splitting strength ratio, and loading times at failure increased by 19.9%, 18.28%, 4.19%, 8.6%, and 9.15%, respectively. Compared with ordinary asphalt mixture, it increased by 47.0%, 28.72%, 7.65%, 15%, and 75.81%, respectively. Moreover, when modified corn stalk fiber is added at 0.2%, the viscoelastic delay time of asphalt mixture is the longest, the strain peak value and rut depth are at a minimum, and the viscoelastic properties, creep properties, and long-term high-temperature properties are the best. [ABSTRACT FROM AUTHOR]

Bulk density and porosity have great influence on the technical performance of an emulsified asphalt mixture, so in order to enhance the strength of the asphalt mixture, bulk density should be improved and porosity should be reduced. Considering the forming process of the emulsified asphalt mixture, the decrease in porosity can ensure the state of the mixture. In order to reduce the porosity of the emulsified asphalt mixture, an innovative forming process is proposed to improve the performance of the emulsified asphalt mixture, and its strength formation mechanism is explored in this paper. Three groups of emulsified asphalt mixtures (ARC-8 + SBR, SMA-5 + EVA, SMA-5 + SBR) were prepared by a conventional mixing process and novel mixing process. Marshall test of the emulsified asphalt mixture, CT scanning test of the emulsified asphalt mixture, workability test and analysis were manufactured and tested. The results show that, compared with conventional methods, the innovative forming method can increase the bulk density of the mixture and reduce the porosity, and thus improve its technical performance. The reason is that most of the water in the mixture of the innovative forming method sticks to the outer surface of the fine aggregate, and the water is more easily discharged. Secondly, the fine aggregate of the innovative forming method is directly mixed with the emulsion, and the volume is smaller. The emulsion wraps the fine aggregate in it due to the surface tension, which enhances the adhesion effect, thus improving the strength of the mixture. [ABSTRACT FROM AUTHOR]

Different test methods have been used to predict the performance of asphalt pavement by addressing the cracking mechanism. Based on the preference shown by highway agencies, the two most prevalent tests are the Indirect Tensile Asphalt Cracking Test (IDEAL-CT) and the Illinois Flexibility Index Test (I-FIT). Both tests conform to the fracture energy–based principle in defining the cracking potential of asphalt concrete at intermediate temperature, and therefore, for quality assurance, many agencies use these tests interchangeably following convenience without comprehending the relationship, if any, between them. Therefore, the study aims to find an equivalency between the tests by evaluating the fracture behavior and different measured parameters that are used to develop the cracking indexes and subsequent performance. In this regard, 11 different mixes have been evaluated to predict the cracking potential following their significant properties. Although both tests consistently identify possibly poor mixes, there is no appreciable proportionality between them. Moreover, the tests exhibit different fracture energy and strength and show individual slopes in failure mechanism trends. In contrast to fracture energy alone, the postpeak slope and the strength of the mixture seem to correlate better with the respective indexes. In general, the tests are not interchangeable; therefore, the selection of a mixture following the index value should be based on carefully observed field performance rather than just convenience. It is also recommended to incorporate the field performance of mixtures to find a better correlation when selecting the appropriate test performance criteria. [ABSTRACT FROM AUTHOR]

Quartzite aggregates have poor adhesion with asphalt binder due to the higher silica content present in the mineral composition. Apart from conventional asphalt mixture testing methods, the surface free energy (SFE)-based adhesion evaluation method is most widely used in recent times to predict compatibility between aggregate and asphalt binder and moisture susceptibility in asphalt mixtures. This study tried to improve quartzite aggregates' adhesion properties by modifying the aggregates' surface with a nano-organosilicon (NOS), and two silane coupling agents (SCA) were used in modifying the aggregates' surface. Results showed that surface modifications by chemical treatments reduced the aggregate's SFE by increasing the aggregate nonpolar components to make a better bond with asphalt binder, which is also a non-polar material. From tensile strength ratio (TSR) results, it is found that the asphalt mixtures prepared with surface-modified aggregates showed better resistance to moisture damage with a 12%–15% increase in TSR. SFE indices like adhesion energy and energy ratio (ER) also showed significant improvement in adhesion between aggregates and asphalt binder, even in the presence of moisture. The ER values were above acceptable limits after surface treatments and showed a 100% increase compared with control mixes. SCA-1 and SCA-2 treatments effectively improved moisture damage in hot-mix asphalt with quartzite aggregates. One-way ANOVA was used to predict the effect of treatment methods and aggregate types on conventional TSR values and advanced SFE indices. The statistical results proved significant improvements in TSR and ER after the treatment of aggregates, but aggregate types do not make significant changes. [ABSTRACT FROM AUTHOR]

Biorejuvenators are rejuvenating agents produced from sustainable biological raw materials. In this study, a biorejuvenator was used in recycled materials, such as reclaimed asphalt pavement (RAP), to determine its effect on the asphalt binder film thickness (ABFT) and resilient modulus (S mix) of an asphalt concrete wearing course (ACWC) mixture, which was tested at the optimum binder content (OBC). The ABFT was investigated using scanning electron microscopy and the S mix was determined from the asphalt mixture test using UMATTA at test temperatures of 20–40 °C. The asphalt mixture was prepared with RAP (0–30%), pen 60/70, aggregates, and two types of biorejuvenators, namely coconut shell bioasphalt (BioCS) and BitutechRAP (from trees). Furthermore, an S mix model was developed for each mixture type. The ABFT value obtained from the microstructural test results for each mixture corresponded with the minimum ABFT requirements for the adhesion criteria of the asphalt mixture, microstructurally demonstrating that the biorejuvenators worked well to restore the performance of 30%RAP in the ACWC mixture. Both types of biorejuvenators could activate the bitumen of the RAP (RA binder) because they could still produce S mix. The value of S mix produced from the RAP and BioCS mixture was greater than that produced from the RAP and BitutechRAP mixture. In the resulting S mix model, the influential volumetric parameters for ACWC + RAP + BioCS and ACWC + RAP + BitutechRAP were the voids in mineral aggregate and voids in asphalt, respectively. Based on the results of the microstructural, mechanistic, and S mix models, BioCS, as a local Indonesian biorejuvenator, has significant potential to rejuvenate recycled materials up to 30%. [ABSTRACT FROM AUTHOR]

In recent years, the increased use of heavy commercial vehicles with higher axle weights has required the development of innovative technologies to improve the mechanical properties of asphalt concrete conglomerates, such as fatigue resistance and rutting. This study offers a comprehensive comparative analysis of different types of asphalt concrete tested in four trial sections (S1, S2, S3, S4) of the SP3 Ardeatina rural road in Rome, under actual traffic and operational conditions. More precisely, the pavement technologies applied include modified asphalt concrete with graphene and recycled hard plastics for S1, asphalt concrete modified with styrene–butadiene–styrene (SBS) for S2, asphalt concrete with a standard polymeric compound for S3, and traditional asphalt concrete for S4. The evaluation approach involved visual inspections in order to calculate the pavement condition index (PCI) and falling weight deflectometer (FWD) tests. In addition, back-calculation analyses were performed using ELMOD software to assess the mechanical properties. The laboratory tests revealed superior properties of M1 in terms of its resistance to permanent deformations (+13%, +15%, and +19.5% compared to M2, M3, and M4, respectively) and stiffness (10,758 MPa for M1 vs. 9259 MPa, 7643 MPa, and 7289 MPa for M2, M3, and M4, respectively). These findings were further corroborated by the PCI values (PCIS1 = 65; PCIS2 = 17; PCIS3 = 28; PCIS4 = 29) as well as the FWD test results after 5 years of investigation, which suggests greater durability and resistance than the other sections. [ABSTRACT FROM AUTHOR]

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In Indonesia, flexible pavement is the primary form of road infrastructure. It is typically produced using a binder combined with Buton Granular Asphalt (BGA B 5/20) as an additional binder. Tire rubber waste as an additive is considered an option to reduce environmental pollution and promote sustainable procurement strategies. The objective of this study is to evaluate the results of the Marshall characteristic test for an asphalt concrete wearing course (AC-WC) with tire rubber used as an asphalt binder. Three AC-WC mixtures (0%, 5%, and 10%) were subjected to Marshall characteristic tests. The results of the Marshall stability test showed that the untreated AC-WC mixture had a stability of 1312 kg, while the AC-WC mixture with 5% tire rubber had a stability of 1150 kg, indicating a reduction of 12.3%. Similarly, the 10% tire rubber demonstrated a stability of 1100 kg, reflecting a reduction of 16.2%. The Marshall Quotient for the standard AC-WC mixture was 416.9 kg/mm. In contrast, the 5% tire rubber yielded a Quotient of 354 kg/mm, representing a decrease of 15.1%. Additionally, the 10% tire rubber resulted in a Quotient of 289.4 kg/mm, indicating a reduction of 30.1%. The Marshall characteristics VMA, VIM, VFB, and Flow also met the standard criteria for AC-WC. The addition of tire rubber reduced the bearing capacity and resistance to permanent deformation of the AC-WC. However, it was observed that tire rubber waste can be effectively used as an additional binder for asphalt in AC-WC treatment. [ABSTRACT FROM AUTHOR]

The search for alternatives to filler used in asphalt pavement has been focused on recently due to the lack of traditional materials sources and the aim of sustainable development goals. Novel environmental protection material—alkali-activated slag (AAS) with a prospective substitution for cementitious binder—has been developed widely; however, the possibility of application of AAS in practice is still under investigation, and hence, mass production of AAS for the testing phase generates significant quantities of solid laboratory waste materials. This study paved the way for safe disposal and evaluating the potential of utilizing AAS as filler in asphalt concrete mixes. To understand the influence of filler types on the performance of asphalt concrete, the physical and chemical properties of AAS filler were analyzed and compared to the conventional limestone (LS) filler by applying laser particle size analysis, scanning electron microscope (SEM), x-ray diffraction (XRD) analysis, and x-ray fluorescence (XRF) spectrometry. The monotonic indirect tensile test (IDT) was adopted to characterize the behavior of asphalt mixes over a range of performances at low, intermediate, and high temperatures; additionally, to practice the balanced mix design (BMD) into quality assurance (QA) of asphalt mixes. Testing methods involving monotonic IDT used in this study are indirect tensile strength (ITS), indirect tensile asphalt cracking test (IDEAL-CT), toughness index (TI) and fatigue index (fi), low-temperature IDT, high-temperature indirect tension (HT-IDT), and moisture susceptibility test. The results indicated that asphalt concrete using AAS filler delivers superior engineering performance, such as resistance to cracking, rutting, and moisture damage, compared to the one made with LS filler. This supports the use of AAS filler as a potential substitution for LS filler in the production of asphalt concrete. Besides, the practice of BMD by implementing monotonic IDT for QA of asphalt mixes showed high feasibility. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to compare the dynamic viscosity and steady viscosity characteristics of high-viscosity modified asphalt binder (HVA) and to analyze the applicability of the Cox–Merz rule as well as of the different zero shear viscosity (ZSV) test methods for HVA. To this end, seven kinds of asphalt binders including base asphalt binder, traditional modified asphalt binder with 4.5% styrene-butadiene-styrene (SBS), commercial HVA, and four self-shearing HVAs were prepared. The frequency sweep test and shear rate sweep test were conducted to obtain dynamic viscosity and steady viscosity, and the Cross model, Carreau model, and Carreau–Yasuda model were used to calculate ZSV based on these two types of viscosity. The results show that both the dynamic and steady viscosity tests prove that asphalt binder exhibits shear-thinning and yield stress behavior. Besides, there is a critical shear rate in the shear rate sweep test and the critical shear rate decreases with the increase of modifier content. The empirical Cox–Merz rule has good applicability in the Newtonian plateau region of base asphalt binder, but it is only applicable to a partial shear-thinning range of modified asphalt binder. Noteworthily, it fails when applied to HVA-C. The frequency sweep test is only suitable for determining the ZSV of base asphalt binder but not applicable at all to the modified asphalt binder because there is no Newtonian plateau in the dynamic viscosity, and the fitting results based on model extrapolation have huge errors as well as vary with the number of iterations. However, the shear rate sweep test is suitable for testing ZSV for both base and modified asphalt binders. Furthermore, it should be pointed out that ZSV obtained by model fitting is not a steady viscosity at zero shear rate but a Newtonian viscosity at a low shear rate, so low shear viscosity (LSV) is a more accurate concept. [ABSTRACT FROM AUTHOR]

Due to viscoelastic characteristics, the strength values of the high-modulus asphalt mixtures (HMAM) obtained under different conditions (temperatures, loading rates, and stress states) are quite different, and the serving conditions of asphalt pavements are also varied. Thus, the strength under fixed conditions cannot reflect the mechanical performances of materials under real serving conditions, which leads to inaccuracies in the asphalt pavement structural design. To develop a precise strength evaluating method for high-modulus asphalt mixtures, the strength tests of high-modulus asphalt mixtures were implemented under different conditions (temperatures, loading rates, and stress states) in this study. The test results indicated that for each stress state, the variation of strength with loading rates under different temperatures can be characterized by power functions, and the variation of strength with temperatures under different loading rates can be characterized by exponential functions. The uniform characterizing model of strength under different conditions was established through the dimensionless method and the sigmoidal function. With the effects of temperature, loading rates, and stress states included, the strength obtained can better reflect the mechanical performances in actual pavement serving conditions. The research results contribute to the improvement of the structural resistance design of the asphalt pavement with high-modulus asphalt mixtures. [ABSTRACT FROM AUTHOR]

A basalt fiber asphalt mixture could improve the road performance of pavements and prolong the service life. The oil/asphalt absorption capacity of basalt fiber affects the road performance of asphalt mixtures to a certain extent. However, using kerosene as the medium to measure the oil absorption rate of bundle fibers by the vibration method, as the Chinese specifications recommends, is unreasonable. Therefore, the aim of this paper is to study the effect of the basalt fiber morphology on the oil absorption rate and the oil/asphalt absorption test methods suitable for asphalt mixtures with different structures (dense-graded and gap-graded), and to also explore the appropriate method to determine the oil/asphalt absorption rate of fiber to kerosene and asphalt. The results showed that the filamentous basalt fiber (FBF) was easier to disperse uniformly in asphalt than the bundled basalt fiber (BBF), and the oil absorption capacity of the FBF could more accurately characterize the actual working state of the fiber in the asphalt mixture. For the gap-graded asphalt mixture, the appropriate method to measure the fiber oil absorption rate is the combination of the vibration and centrifugation methods, while the fiber asphalt absorption rate is measured by the vibration method. For the dense-graded asphalt mixture, the combination of the extrusion and centrifugation methods are more reasonable to determine the fiber oil absorption rate, while the extrusion method is suitable for determining the fiber asphalt absorption rate. The concept of an effective fiber oil absorption rate is proposed to characterize the ability of fiber to adsorb kerosene in asphalt mixtures with different structures. A temperature of 160 °C is recommended as the test temperature to determine the fiber asphalt absorption rate. Kerosene as the asphalt absorption test medium could not directly reflect the ability of fiber to adsorb asphalt. [ABSTRACT FROM AUTHOR]

The main purpose of this study was to understand the failure mechanism of fly ash fiber–reinforced asphalt specimens under uniaxial compression loading and splitting loading, respectively. The variation of acoustic emission (AE) parameters in the acoustic emission tests during this fracture process was analyzed. The results showed that under uniaxial compression, the failure process of the fiber asphalt specimens could be divided into four stages: the formation of internal microcracks, microcrack propagation, rapid crack propagation, and finally, failure. Shear failure is the main failure form of asphalt specimens, and with the gradual increase of fiber content, the failure mode of specimens gradually changes from shear failure to shear-tensile failure. The correlation analysis between peak value and frequency of acoustic emission parameters shows that there are three frequency bands of fly ash fiber asphalt specimen, namely, 0–30, 30–60, and 150–200 kHz, which correspond to the initial dislocation failure of the interface between aggregate and asphalt mortar, the fracture failure of the interface between fly ash fiber and asphalt mortar, and the complete dislocation failure of the interface between aggregate and asphalt mortar. In recent years, acoustic emission technology has been widely used in the field of nondestructive testing of cement concrete and bridge structures. Nevertheless, the damage identification methods commonly used in asphalt pavement, such as the computational simulation method and image processing method, have low working efficiency, large error, and lack of dynamic perception of the whole damage process, which limits their applicability in practical engineering applications. In this paper, acoustic emission technology has been employed to characterize the damage and crack propagation law of fiber asphalt specimens under various stress states. Through the analysis of the evolution characteristics of acoustic emission signal parameters, the fracture damage characteristics of fiber asphalt samples under different stresses are invested. The research results are of great significance for the popularization and application of acoustic emission technology in the field of nondestructive testing of asphalt pavement. [ABSTRACT FROM AUTHOR]

In the asphalt pavements, which are prepared by mixing bitumen and aggregates, fatigue cracking and thermal cracking failure occur due to continuous loading and climate conditions. Extending the life of asphalt pavements is very important from an environmental and economic point of view. In this study, reactions are conducted to investigate the effects of six ionic liquids (IL) with different side-chain lengths on the self-healing properties of bitumen. Thermogravimetric analysis and differential scanning calorimetry analysis are performed for ionic liquid characterization, while for bitumen characterization, Saturates, Aromatics, Resins, Asphaltenes (SARA) fractionation of bitumen and Gel Permeation Chromatography, Nuclear Magnetic Resonance, Elemental Analysis of these sub-fractions were performed. In addition, two new test methods have been developed to measure the self-healing capacity of bitumen. The first method shows the effects of rest times when intermittent loading is applied to the sample at high temperatures, while the other method was developed to demonstrate the self-healing ability of bitumen at low temperatures with long rest periods. Stripping tests, asphalt fatigue tests and zeta potential measurements are done to investigate the effects of ionic liquids on bitumen and aggregate interactions. The results indicated that different ionic liquids have different effects on asphalt self-healing mechanism. IL improved the self-healing performance of asphalt 40% at high temperatures, and 100% at low temperature while stripping properties 25% and asphalt fatigue life 20% improved. Therefore, it can be concluded that different bitumen-IL modification recipes could be used for self-healing of asphalt pavements, depending on climatic conditions and traffic density. [ABSTRACT FROM AUTHOR]

Recycling agents (RAs) can mitigate the adverse effects of reclaimed asphalt pavement (RAP) on recycled asphalt, which can result in more RAP being added. To explore the effects of four RAs on recycled asphalt, this study used asphalt rheological performance experiments, including the bending beam rheometer (BBR) test, the dynamic shear rheological (DSR) test, and the indirect tensile asphalt cracking test (IDEAL-CT), to study the performance grade (PG), cracking resistance, and cracking susceptibility of recycled asphalt. In addition, an aging model for asphalt was used, and short-term and long-term aging sensitivities were evaluated according to this model. Results showed that US Soybean significantly enhanced the high-temperature and low-temperature performance grade (PGLT) and cracking resistance and reduced cracking sensitivity of the recycled asphalt. In addition, the short-term aging sensitivity was the lowest. It showed the best regeneration effect. However, the recycled asphalt with US Soybean showed the highest long-term aging sensitivity, suggesting that longer aging time results in poorer performance. Ingevity's PG, cracking resistance, and cracking sensitivity are slightly lower than that of US Soybean, and Ingevity demonstrated the second lowest short-term aging sensitivity. However, its prolonged aging sensitivity was much lower than that of US Soybean. Asphalt and Wax Innovations and Georgia Pacific agents slightly improved recycled asphalt properties. The long-term aging sensitivity of recycled asphalt with four Ras was higher than that of recycled asphalt without Ras. These results indicated that the recycled asphalt's performance with Ras worsened as aging time increased compared to the original recycled asphalt. [ABSTRACT FROM AUTHOR]

Amorphous carbon powder (ACP), an industrial waste material, is a potential asphalt binder modifier. In this study, the effect of ACP on the rutting performance of asphalt binders and mixtures was investigated. For this purpose, the frequency sweep, and multiple stress creep recovery tests of asphalt binders and resilient modulus, dynamic creep, and wheel tracking tests of asphalt mixtures were conducted on asphalt binders and mixtures containing 3, 5, and 10% of ACP by weight of total asphalt binder. The results showed that using 10% ACP caused a substantial improvement in the rutting parameter of asphalt binders, and the non-recoverable creep compliance values at both 0.1 and 3.2 kPa stress levels decrease by about 80% when modified with 10% ACP. The asphalt mixture results indicated that the indirect tensile strength, wheel tracking, and resilient modulus at 25°C enhanced by about 25%, 43%, and 40%, respectively when 10% ACP modified asphalt binder was used. Therefore, in addition to being a positive action in environmental protection, modifying asphalt binders with 10% ACP can improve the high-temperature performance of asphalt binders and mixtures. [ABSTRACT FROM AUTHOR]

Master curve technique is frequently used to characterize the linear viscoelasticity of polymer modified asphalt (PMA), however, there is no widely accepted master curve for PMA. This study aims to propose a novel double sigmoidal model that can be used universally for all asphalts, especially highly modified PMAs. To do so, one plain asphalt and six representative PMAs are examined. Extended temperature sweep tests (−40°C to 140°C) are conducted to grasp the whole picture of the master curve. Three representative mathematical models (CAM, sigmoidal, double sigmoidal) are selected and compared in terms of fitting in both modulus and phase angle. The results suggest that double sigmoidal model suits all types of asphalts for all testing temperature ranges, and it features the ability to model the rubbery state and rubbery-viscous transition of highly modified PMA (RMSE < 0.02). A phase angle expression of the double sigmoidal model is also developed, which shows great potential in characterizing the strength of polymer network within the PMA. Also, it avoids the impact from the partial break of the time-temperature superposition principle (TTSP) and reveals the true shape of the phase angle master curve. Finally, master curve models are recommended based on different testing temperature ranges. [ABSTRACT FROM AUTHOR]

Ground penetrating radar (GPR) is widely used in nondestructive tests of asphalt pavements, but the characteristics of its detection data need to be extracted manually, and it is very difficult to determine the hidden distress efficiently and accurately inside the asphalt pavement. Therefore, to recognize hidden distress inside asphalt pavement intelligently and improve the efficiency and accuracy of GPR for asphalt pavement detection, this research used the convolutional neural network (CNN) algorithm combined with GPR detection technology. Significantly, the image of the dielectric properties distribution of the road was obtained by processing the GPR detection data, and the GPR detection image data set was established. Moreover, this research dealt with the imbalance of the data set by weighting the loss value. Next, this research designed a CNN model with a simple structure, called visual GPR (VGPR), and used the GPR image data set to train, validate, and test the VGPR. Finally, the model was fine-tuned according to the results, and the optimal hyperparameters were selected. The results show that VGPR converges fast in the training process, and no obvious overfitting phenomenon exists. During the test, the weighted average F1 score in the comprehensive metrics reached 99.626%, indicating that VGPR has excellent generalization performance. When VGPR uses a graphics processing unit for computing, the image recognition efficiency can meet the engineering requirements. A comparison of VGPR with other CNN models reveals that when using the same GPR detection image data set, VGPR has the best recognition effect. In summary, the method detailed herein can quickly and accurately identify the hidden distress of the asphalt pavement and provide a guarantee for the maintenance and operation of the expressway. [ABSTRACT FROM AUTHOR]