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In this research, five fracture criteria (maximum tangential stress (MTS), generalized maximum tangential stress (GMTS), minimum strain energy density (SED), generalized minimum strain energy density (GSED), and modified maximum tangential stress (MMTS)) were evaluated for asphalt concrete using fracture data from tests conducted under various loading modes and conditions. Tests were performed on semi‐circular bend (SCB) specimens of various sizes. Based on the results, the MTS criterion tends to overestimate fractures, while the GMTS criterion exhibits more precise predictions. The SED and GSED criteria inaccurately predict fractures, especially under certain loading conditions. The MMTS criterion shows superior predictive capability for asphalt concrete fractures. Specimen size influences fracture resistance, with larger specimens exhibiting higher fracture values. Overall, the MMTS criterion closely mirrors the crack growth behavior of asphalt concrete, highlighting its precision in predicting fracture results. The errors between the predictions of the fracture criteria MTS, GMTS, SED, GSED, and MMTS, and the experimental results ranged from 0% to 42.8%, 0% to 22.5%, 0% to 52.7%, 0% to 42.4%, and 0% to 14.5%, respectively. Highlights: Fracture tests were conducted on asphalt concrete under various conditions such as temperatures, loading rates, SCB specimen sizes, and loading modes.Five fracture criteria (MTS, GMTS, SED, GSED, MMTS) were assessed for their applicability to asphalt concrete.The MMTS criterion was found to have the best ability to predict fractures in asphalt concrete compared to the other criteria studied.The size of the specimen has an impact on fracture resistance, with larger specimens showing higher fracture values. All the fracture criteria used in the study accurately reflect this trend. [ABSTRACT FROM AUTHOR]

Engineering materials in constructed systems in service exhibit complex patterns, including structural damage, environmental artifacts, and artificial anomalies. In recent years, machine vision methods have been extensively studied, most of which train models using regular grey or color images in the visible bands and label at pixel levels with a large volume of data. The authors propose using hyperspectral imaging (HSI) for structural material condition assessment in this work. Compared with visible images, the research challenge is that HSI pixels with high-dimensional spectral profiles are beyond human perceptive capabilities with hidden discriminative power. Learning from labeled and unlabeled data is one direct approach to unlocking this power. A deep neural network-enabled spatial-spectral feature extraction and a semisupervised learning architecture were developed in this work. A human-in-the-loop (HITL) framework was comparatively studied with three incremental training-data configuration schemes. The paper concludes with the following empirical findings: (1) fully supervised learning determines the baseline of the detection performance; (2) an extensive range of ratio values exists between the unlabeled and the labeled data for incremental semisupervised learning, and a 1∶1 ratio can be taken as a conservative and operational ratio; and (3) with parametric semisupervised learning with equal labeled and unlabeled data participation, the proposed HITL operational workflow can be implemented as a practical approach for HSI-based structural material and damage detection. [ABSTRACT FROM AUTHOR]

This paper summarizes the results of a study that was conducted to evaluate the performance of field-produced aramid fiber-reinforced asphalt mixtures used for resurfacing applications and compare it to that of polymer-modified asphalt mixtures. Twelve test sections were constructed as part of resurfacing projects in Ohio. Two aramid fibers from different sources were used in these projects. During the construction of the test sections, loose asphalt mixtures were collected and were used to prepare samples. Different tests were conducted on the prepared samples. These included the following: semicircular bend and indirect tensile asphalt cracking to evaluate the cracking resistance of prepared samples, the asphalt concrete cracking device test to evaluate the low-temperature cracking resistance of prepared samples, and the Hamburg wheel tracking test to evaluate the resistance of samples to rutting and moisture damage. Results indicated that the effects of the addition of aramid fiber to asphalt mixture vary depending on the type of aramid fiber and mixture properties. In general, Fiber A and Fiber B significantly improved the cracking resistance of mixtures with PG 64-22. Furthermore, mixtures with PG 64-22 binder and aramid fibers had similar or higher cracking resistance as compared to those with PG 70-22M asphalt mixture. The addition of fibers improved the resistance of reinforced mixtures to rutting and moisture damage. The fibers slightly improved the low-temperature cracking resistance of asphalt mixtures. Statistical analysis of testing results indicated that the properties related to the cracking resistance of the fiber mixtures did not significantly change during production. [ABSTRACT FROM AUTHOR]

This paper aims to introduce a highly efficient computational model compared to the current cycle-by-cycle simulation strategy to compute the viscoelastic responses of asphalt concretes and pavement structures under large numbers of load cycles. An explicit constitutive relation for viscoelastic solids in multiple time scales was developed based on the temporal homogenization. The original initial-boundary value problem was divided into a global part in the slow time scale and a local part in the fast time scale. Two simulation studies were presented to validate the computational accuracy and efficiency of the proposed model: (1) a cylindrical asphalt concrete subject to a uniaxial cyclic compression load, and (2) a pavement structure subject to a locally cyclic loading. The laboratory test results and field measurements were compared with the modeled responses to validate the models before comparing with the reference solutions. Results indicate that the temporal homogenization-based viscoelastic model saves considerable computational cost and maintains a satisfactory accuracy. The absolute values of relative error of the modeled responses between the time homogenization and reference solutions are lower than 1% and 4% for the cylindrical asphalt concrete and pavement structure under locally cyclic loadings, respectively. Based on the proposed computational approach, only 4 min are needed to model the response of a cylindrical asphalt concrete subject to 104 repeated load cycles under a uniaxial compression load. The computational time is reduced from 7 h of the reference solution to 38 min of the temporal homogenization solution to model 103 load cycles of a viscoelastic pavement structure. Practical Applications: This study introduces a highly efficient computational model to compute the viscoelastic responses of asphalt concretes and pavement structures under large numbers of load cycles. Multiple time scales were applied to an explicit constitutive relation of asphalt concretes to obtain the formula of global and local initial-boundary value problems. Its computational accuracy and efficiency were verified by comparing the temporal homogenization-based solutions with the testing results and reference solutions for a cylindrical sample and a pavement structure. It is the basis for the long-term pavement performance prediction after including the fatigue damage analysis in the present temporal homogenization framework. By successfully implementing a mechanistic framework for the long-term pavement performance prediction, the pavement design can more rely on the material inherent properties instead of using redundant empirical transfer functions. It is promising that the local calibrations of the current empirical performance transfer functions can be minimized as the proposed pavement long-term performance predictions depend on the material inherent properties and constitutive models. [ABSTRACT FROM AUTHOR]

End-of-life tire (ELT) rubber has been widely researched to replace aggregates in construction materials such as asphalt concrete and cementitious composites. Although most studies paid attention to its effect on engineering properties and the durability of the materials, very few considered chemical reactions with pore solution and the potential for environmental leachate, especially rubberized stabilized soil, which was proposed recently to increase the use of ELT rubber in civil engineering. This study proposes the use of rubberized stabilized soil (RSS) in which clayey soils (e.g., kaolin and bentonite) were stabilized by portland cement (PC) and end-of-life tire (ELT) rubber particles. The authors previously developed a methodology to extract zinc from the ELT rubber; therefore, this study explores the potential for RSS to immobilize the leachate from the ELT rubber before and after this treatment. Three main topics are addressed in this study: (1) the capability of clay to capture leached zinc under ambient and alkaline aqueous conditions; (2) engineering properties of RSS [i.e., unconfined compressive (UCS), flow] with 0%, 10%, 30%, and 50% ELT rubber added by clay volume; and (3) pore solution and leachability tests of RSS. A leaching experiment was employed for Topic 1, UCS and flow tests were conducted for Topic 2, and pore solution extraction and leaching tests were performed for Topic 3. The results showed that the clayey soils and ELT rubber are synergistic in terms of engineering properties and the capturability of zinc and total organic carbon (TOC). Although the ELT rubber and PC strengthen the clay structure, the clay absorbs leached zinc and TOC from the ELT rubber particles. Adding untreated ELT rubber into PC-stabilized clays significantly increased the RSS strength; however, this improvement was less significant for the treated ELT rubber. Ultimately, the results proved that the environmental and mechanical performance of RSS makes it a viable construction material. [ABSTRACT FROM AUTHOR]

To investigate the effect of hot and humid environmental factors on the mechanical properties of asphalt mixtures research, in this paper, the dynamic modulus of asphalt mixtures under the effects of aging, dry–wet cycling, and coupled effects of aging and dry–wet cycling were measured by the simple performance tester (SPT) system, and the dynamic modulus principal curves were fitted based on the sigmoidal function. The results show that under the aging effect, the dynamic modulus of asphalt mixture increases with the aging degree; the dynamic modulus of short-term aged, medium-term aged, long-term aged, and ultra-long-term aged asphalt mixtures increased by 9.3%, 26.4%, 44.8%, and 57%, respectively, compared to unaged asphalt mixtures at 20 °C and 10 Hz; the high-temperature stability performance is enhanced, and the low temperature cracking resistance performance is enhanced; under the dry–wet cycle, the aging effect of asphalt water is more obvious in the early stage, and dynamic modulus of resilience of the mixture is slightly increased. In the long-term wet–dry cycle process, water on the asphalt and aggregate erosion increased, the structural bearing capacity attenuation, and the dynamic modulus of rebound greatly reduced at 20 °C and 10 Hz. For example, the dynamic modulus of asphalt mixtures with seven wet and dry cycles increased by 3% compared to asphalt mixtures without wet and dry cycles, and the dynamic modulus of asphalt mixtures with 14 cycles of wet and dry cycles and 21 cycles of wet and dry cycles decreased by 10.8% and 16.5%, respectively, compared to asphalt mixtures without wet and dry cycles. The main curve as a whole shifted downward; the high-temperature performance decreased significantly; in the aging wet–dry cycle coupling, the aging asphalt mixture is more susceptible to water erosion, and the first wet–dry cycle after the mix by the degree of water erosion is relatively small, along with the dynamic modulus of rebound. The dynamic modulus of resilience is relatively larger, and the high-temperature performance is relatively better, while the low-temperature performance is worse. [ABSTRACT FROM AUTHOR]

In this paper, the accelerated creep under uniaxial tension of hot fine-grained dense asphalt concrete at temperatures of 22–24 °C and stresses from 0.084 MPa to 0.596 MPa is experimentally investigated. The names and brief descriptions of the creep curve and accelerated creep characteristics are given. A mathematical model is proposed that has physical meaning and satisfactorily approximates the asphalt concrete accelerated creep. The model parameters are determined by the Levenberg–Marquardt method. The deformation and time characteristics of the accelerated creep of asphalt concrete are established and analyzed. [ABSTRACT FROM AUTHOR]

The aggregate gradation of asphalt mixture is one of the most important factors affecting the service life of asphalt pavement. In order to study the gradation of asphalt mixture with the best comprehensive performance, this study puts forward a new method of mineral aggregate gradation optimization based on the fuzzy analytic hierarchy process and comprehensive evaluation method, aiming at the multi-level and multi-index evaluation of the road performance of asphalt mixture. First, the orthogonal test design method is applied to design nine target gradations with coarse aggregate (>4.75 mm) and fine aggregate (<4.75 mm) of AC-20 (asphalt concrete) mixture serving as two factors and the upper, middle, and lower positions of the gradation curve as three levels, and then the road performance test research is carried out. Second, a comprehensive model for evaluation of road performance of mineral aggregate gradation is established. A fuzzy complementary judgment matrix is constructed, and the index weights of each level and the hierarchical total ranking weight are calculated. Then, the membership function is introduced into the comprehensive evaluation model for the road performance of mineral aggregate gradation, and the membership values of each index of asphalt mixture road performance are obtained. Finally, the fuzzy comprehensive evaluation method is used to find out the comprehensive evaluation value of the road performance of the nine graded asphalt mixtures, and the mineral aggregate gradation is optimized. The research results show that the 1# gradation of the asphalt mixture has the highest comprehensive road performance evaluation value, and the combination of the fuzzy hierarchical analysis process and comprehensive evaluation method can more objectively and comprehensively evaluate the comprehensive road performance of the asphalt mixture and provide a useful reference for the optimal selection of asphalt mixture mineral gradation. [ABSTRACT FROM AUTHOR]

AbstractInsufficient adhesion between ultrathin wearing courses (UTWCs) and substrate layers can result in pavement distress. Epoxy asphalt exhibits potential as a tack coat due to its high bonding strength and thermal stability. However, its rapid curing may pose challenges to construction schedules. This study aimed to optimize the formulations of epoxy asphalt tack coats (EATCs) to enhance the interfacial adhesion and working performance of UTWCs. The adhesion of EATCs was evaluated through rotational viscosity and tensile tests. Design parameters were optimized using analysis of variance and microscopic tests. Road performance was assessed via interlayer shear and tensile testing on three pavement structures. The results indicated that the curing agent strongly influenced the properties and curing kinetics of EATCs. Formulations containing complex polysebacic polyanhydride (CPSPA-EA) exhibited superior bonding while meeting construction schedules. Microscopic analysis of CPSPA-EA revealed a stable crosslinked network formed at 30% binder dosage. The amount of spraying significantly impacted the adhesion in UTWC structures. The optimal spraying amounts were 0.60 kg/m2 for asphalt concrete (AC-13), 0.55 kg/m2 for stone matrix asphalt (SMA-13), and 0.40 kg/m2 for cement concrete substrate layers. These findings presented an optimization framework for designing EATCs to enhance UTWCs working and long-term performance through balanced tack formulations and application parameters. [ABSTRACT FROM AUTHOR]

This study examines the strategic incorporation of various recycled materials into asphalt concrete, specifically focusing on municipal solid waste incineration bottom ash (MSWI BA), recycled asphalt shingle (RAS), and recycled concrete aggregate (RCA). Due to the high porosity of MSWI BA and RCA, and the significant asphalt binder content (30–40%) found in RAS, there is a need to increase the amount of liquid asphalt used. RAS is posited as an efficient substitute for the asphalt binder, helping to counterbalance the high absorption characteristics of MSWI BA and RCA. The research objective is to quantitatively evaluate the effect of the combined use of RAS, MSWI BA, and RCA in Hot Mix Asphalt (HMA). This study encompasses several laboratory evaluations (i.e., rutting and tensile strength tests) and a cost–benefit analysis, which is a life cycle cost analysis. The results indicate that the combined use of these materials results in a higher tensile strength and rut resistance when compared with the control (with virgin aggregate). According to the cost–benefit analysis result, when the three recycled materials are used for an HMA overlay over an existing aged pavement, it could be 60–80% more cost-effective compared to a conventional HMA overlay, thereby offering significant economical savings each year in the field of road construction. [ABSTRACT FROM AUTHOR]

High-performance asphalt concrete is an innovative paving material that typically relies on the properties of polymer-modified asphalt binders. However, the application is limited due to their high cost and phase separation issues. A solution is explored in the present study by blending 12% asphaltenes and a straight-run asphalt binder with a true performance grade of 70.2–25.9, resulting in a true performance grade of 82.9–21.8, which elevates the binder's stiffness. Three lengths of polyethylene terephthalate fibres are used to improve the cracking resistance of these asphaltenes-modified mixes. An indirect tensile cracking test is conducted at 25 and 37 °C, revealing a significant improvement in cracking tolerance and failure energy, particularly at 37 °C. The cracking tolerance index value peaked at 105 for 12 mm polyethylene terephthalate fabricated sample, while control asphaltenes-modified, 6 mm, and 18 mm polyethylene terephthalate fabricated samples achieved 61, 87, and 99, respectively, with failure energy increasing with longer fibres. [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]

Moisture-induced damage is a serious problem that severely impairs asphaltic pavement and affects road serviceability. This study examined numerous variables in asphalt concrete mixtures to assess their impact on moisture damage resistance. Mix design parameters such as the asphalt content (AC) and aggregate passing sieve No. 4 (PNo. 4) were considered as variables during this study. Additionally, hydrated lime (HL) was utilized as a partial substitute for limestone dust (LS) filler at 1.5% by weight of the aggregate in asphalt concrete mixtures for the surface layer. This study also investigated the potential enhancement of traditional asphalt binders and mixtures by adding nano-additives, specifically nano-silica oxide (NS) and nano-titanium dioxide (NT), at rates ranging from 0% to 6% by weight of the asphalt binder. To quantify the moisture damage resistance of the asphalt concrete mixes, two types of laboratory tests were employed: the tensile strength ratio (TSR) and the index of retained strength (IRS). The former characterizes moisture damage using tensile strength, whereas the latter uses compression strength. The physical properties of the asphalt binder, such as its penetration, softening point, and ductility, were also evaluated to identify the effects of the nanomaterials. The results indicated that variations in the mix design variables significantly affected the moisture damage resistance of the asphalt concrete mixtures. The maximum improvement values were obtained at the optimum asphalt content (OAC) and PNo. 4 (mid-range + 6%) with TSR values of 80.45 and 82.46 and IRS values of 74.39 and 77.14, respectively. Modifying asphalt concrete mixtures with 1.5% HL resulted in improved moisture resistance compared with mixtures without HL (0% HL) at each PNo. 4 level, reaching superior performance at PNo. 4 (mid-range + 6%) by 4.58% and 3.96% in the TSR and IRS tests, respectively. Additionally, both NS and NT enhanced the physical properties of the asphalt binder, leading to substantial enhancements in asphalt concrete mixture performance against moisture damage. A 6% dosage of NS and NT showed the best performance, with NS performing slightly better than NT. TSR was increased by 14.72 and 11.55 and IRS by 15.60 and 12.75, respectively, with 6% NS and NT compared with mixtures without nanomaterials (0% NM). [ABSTRACT FROM AUTHOR]

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The structural performance of asphalt concrete is highly dependent on its thermal properties, especially in regions where daily or seasonal temperature variations are significant. In mechanistic design methods, thermal properties (specific heat, thermal conductivity, and coefficient of thermal expansion) are necessary to estimate the thermal behavior of asphalt concrete. However, the measurement of these properties is still a challenge, not only because of the heterogeneous structure of asphalt concrete but also because of the limitations imposed by the size of the test samples and the reliability of the measurement methods. In this study, a practical method, the Transient Plane Source (TPS), is proposed to measure the thermal conductivity of laboratory-produced asphalt concrete samples. To determine how thermal conductivity is affected by the maximum aggregate size, air voids, and aggregate source, a series of asphalt mixtures are compacted using the Superpave gyratory compactor to produce test samples. To determine the possible relationship between microstructural and thermal properties, which has not been investigated in previous studies, an image analysis is also performed to calculate the number of contact points and the total aggregate area in each sample. The statistical analyses show that all mixture properties, i.e., maximum aggregate size, air void content, and aggregate source, are significant, with the aggregate source having the greatest influence on the thermal conductivity of the samples. It is also shown that the TPS method is sensitive to the properties of the contact area, which significantly affects the reliability of the measurements. [ABSTRACT FROM AUTHOR]

In this study, asphalt mixtures made by steel slag (SSA), copper slag (CSA), limestone (LA) and siliceous (SA) aggregates were subjected to different aging conditions; and were evaluated using Marshall, indirect tensile strength (ITS), Cantabro abrasion loss and semi-circular bending (SCB) tests. Results reveal that the moisture damage, raveling and fracture resistance of asphalt mixture decrease with aging and the ITS and Marshall properties improve with aging. After 7-day long-term aging, the TSR of the mixtures made by LA, SA, SSA and CSA, decreases, 28.8%, 48.5%, 8.8% and 15%, respectively, while, the ITS in dry condition increases, 61.9%, 33%, 62% and 81%, respectively. The fracture properties and moisture damage resistance of asphalt concrete made by SSA and CSA are less affected by aging than those made by LA and SA. Statistical analysis revealed that the effect of aggregate type, aging condition and their interaction on the mixture properties is significant. [ABSTRACT FROM AUTHOR]

The bond properties at layer interfaces are a required input in mechanistic asphalt pavement models. For design and analysis procedures, involving the calculation of key responses that are commonly linked to performance, perfect bond conditions are regularly assumed between layers. One emerging approach for prolonging the service life of asphalt pavements, either new or rehabilitated, is installing asphalt grid reinforcement (AGR) products between paving lifts. In these cases, the perfect bond assumption may not hold – undermining the reinforcement potential. Accordingly, the objective of this study was to investigate the effects of layer interface properties on key responses in pavements with AGR. The investigation was carried out by combining results from a full-scale construction, laboratory tests on asphalt concrete (AC) cores, and synthetic simulations. The latter were performed with a recently developed semi-analytic mechanistic code that can accept AGR products. This code can handle time- and temperature-dependent layer and interface properties, as well as moving loads. From the laboratory tests, it was found that the bond between AC lifts, with and without an AGR, is time- and temperature-dependent – best characterised by a relaxation interface stiffness function. This relaxation function was measured to be consistently larger without an AGR than with an AGR. Nonetheless, pavement simulations showed that including an AGR has no pronounced effect on strain magnitudes under high-speed/low-temperature conditions, can lessen horizontal strain magnitudes at the reinforced interface and at the AC bottom (mainly under slow-speed/high-temperature conditions, and depending on the installation depth of the AGR), and has no pronounced effect on deflections regardless of the loading speed and temperature level. It is concluded that even if laboratory measurements display a reduced interface stiffness when including an AGR, the reduction may not have any practical implication on key pavement responses, and the reinforcement potential is not necessarily undermined. The modelling and experimental approaches outlined and utilised in this study offer a rational tool for analysing this matter/question on a case-by-case basis. [ABSTRACT FROM AUTHOR]

The longevity of waste asphalt can be considerably improved through cold recycling techniques combined with various additives. This research investigates the cold regeneration of aged asphalt concrete using Reclaimed Asphalt Pavement (RAP), Portland cement, cationic bitumen emulsion, and additional aggregates. The primary goal is to evaluate the performance enhancements in terms of average density, compressive strength, water resistance, and swelling across different mix compositions. Three distinct mixtures were formulated and assessed. Mix No. 1, composed solely of RAP, showed the lowest average density and highest swelling, indicating poor performance due to the lack of binding agents. Mix No. 2, which incorporated RAP, Portland cement, and water, exhibited the highest density and compressive strength, highlighting the crucial role of Portland cement in improving structural integrity. Mix No. 3, a more complex mixture including RAP, aggregates, Portland cement, water, and bitumen emulsion, displayed balanced properties with enhanced moisture resistance and reduced swelling. The experimental findings emphasize the effectiveness of adding Portland cement and bitumen emulsion to improve the mechanical and durability characteristics of recycled asphalt mixtures. Specifically, Mix No. 2 and Mix No. 3 demonstrated significant performance improvements, making them suitable for road maintenance applications. This study advocates for the widespread use of cold recycling methods with additive integration to achieve sustainable and cost-effective pavement restoration solutions. [ABSTRACT FROM AUTHOR]

The article experimentally investigated unsteady-state creep of a hot fine-grained dense asphalt concrete under uniaxial tension at temperatures of 22-24 °C. 61 samples of the asphalt concrete in the form of a rectangular beam with dimensions of 50 x 50 x 150 mm were tested to complete failure at seven different stresses (from 0.084 MPa to 0.3053 MPa) in a special installation with a heat chamber. Based on the test results, unsteady-state creep curves were constructed, which were normalized and approximated with high accuracy by a power function. Reliable dependences of the limiting time of hardening, the limiting strain of hardening, and the hardening rate on stress have been established. [ABSTRACT FROM AUTHOR]

The dual nature of asphalt binder necessitates improvements to mitigate rutting and fatigue since it performs as an elastic material under the regime of rapid loading or cold temperatures and as a viscous fluid at elevated temperatures. The present investigation assesses the effectiveness of Nano Alumina (NA), Nano Silica (NS), and Nano Titanium Dioxide (NT) at weight percentages of 0, 2, 4, 6, and 8% in asphalt cement to enhance both asphalt binder and mixture performance. Binder evaluations include tests for consistency, thermal susceptibility, aging, and workability, while mixture assessments focus on Marshall properties, moisture susceptibility, resilient modulus, permanent deformation, and fatigue characteristics. NS notably improves binder viscosity by about 138% and reduces penetration by approximately 40.8% at 8% nanomaterial (NM) content, significantly boosting hardness and consistency. NS also enhances Marshall stability and decreases air voids, increasing the mix's durability. For moisture resistance, NS at 8% NM content elevates the Tensile Strength Ratio (TSR) to 91.0%, substantially surpassing the 80% standard. Similarly, NA and NT also show improved TSR values at 8% NM content, with 88.0% and 84.1%, respectively. Additionally, NS, NA, and NT reduce permanent deformation by 82%, 69%, and 64% at 10,000 cycles at 8% NM content, illustrating their effectiveness in mitigating pavement distress. Notably, while higher NM content generally results in better performance across most tests, the optimal NM content for fatigue resistance is 4% for NS and 6% for both NA and NT, reflecting their peak performance against various types of pavement distresses. These results highlight the significant advantages of nanoparticles in improving asphalt's mechanical properties, workability, stability, and durability. The study recommends further field validation to confirm these laboratory findings and ensure that enhancements translate into tangible improvements in real-world pavement performance and longevity. [ABSTRACT FROM AUTHOR]

Roadways are the main transportation mode in Brazil for both cargo and people. This strong dependence on road transport makes paving highways extremely important for the country's development. A common way to recover deteriorated pavement is through a superficial reinforcement called overlay. The whitetopping overlays are made of Portland cement concrete. The technique basically consists of building a concrete pavement over the existing asphalt pavement. The existing pavement acts as a sub-base for the concrete overlay. The addition of fibers to concrete has been increasingly frequent, especially for industrial floors and pavements, bringing longer performance life for same traffic, climate and concrete strength. The fibers promote the improvement of several characteristics of the concrete paste, such as the increase in post-cracking toughness, energy absorption, and fracture energy. This work evaluates the flexural response of composite beams of concrete and asphalt layers and the influence of adding fibers to the concrete. An experimental program is set and supports the development and validation of a finite element numerical model. The numerical model is then applied to a parametric study where tendifferent concrete mixes with different types of fibers and contents are analysed. Steel and synthetic fibers are used. The composite beams are simulated indicating the concrete mixes that best supported loads in the post-cracking regime, with some mixes managing to maintain around 90% of the peak load for large crack openings. [ABSTRACT FROM AUTHOR]

One of the most popular rehabilitation methods used for distressed asphalt concrete pavements is use of bonded concrete overlays on asphalt pavements (BCOA). A new procedure, "Bonded Concrete Overlay of Asphalt Mechanistic-Empirical Design (BCOA-ME)," has been developed at the University of Pittsburgh to address significant limitations of similar procedures that have been used by state highway agencies (SHAs) over the years. A portion of the BCOA-ME procedure, renamed Short Jointed Plain Concrete Pavement over Asphalt Concrete (SJPCP/AC), was recently added to AASHTOWare Pavement ME Design (PMED) Software package. Longitudinal fatigue cracking calculated in terms of percentage of slabs is predicted as output distress by the PMED software. This study reports comprehensive sensitivity results for PMED design inputs to predicted longitudinal fatigue cracking. To help understand the impact of climate on the predictions, five climate locations representing different climatic conditions were considered. Normalized sensitivity index (NSI) values were evaluated by performing one-at-a-time (OAT) sensitivity analyses. A summary of results based on evaluated NSI ranking is presented for the varying design periods and reliability levels considered by the PMED software. [ABSTRACT FROM AUTHOR]

The objective of the study was to evaluate the sensitivity of different input variables on the flexible pavement design thickness of high-speed, high-traffic routes in South Carolina using the Mechanistic-Empirical Pavement Design Guide (MEPDG) by means of the AASHTOware Pavement ME design software. A combination of MEPDG input levels (Levels 1, 2, and 3) were used for pavement analysis based on the availability of data. The variables considered in this investigation included two-way average annual daily truck traffic (AADTT), asphalt mix type, climate station, subgrade type and resilient modulus, and aggregate base thickness. This study mainly focused on the bottom-up fatigue cracking, and individual pavement designs were evaluated to determine the asphalt concrete (AC) thickness for which the total bottom-up cracking was equal to 2% lane area after a 20-year design period. The results indicated that the asphalt mix type did not have significant impact on the pavement thickness. One of the five climate stations evaluated resulted in significantly thicker pavements than the others. Subgrade type, as well as resilient modulus, had a significant effect on the pavement thickness. Finally, pavements were more sensitive to total truck traffic changes at lower AADTT values and then became somewhat less sensitive when exposed to the highest levels of traffic. The results of this study could potentially be used to develop a preliminary asphalt thickness design catalog for interstate routes in South Carolina. [ABSTRACT FROM AUTHOR]

Mesostructure-based simulation technology offers an effective approach to modeling the mesomechanical responses of asphalt concrete and studying its mesomechanisms. However, current exploration depth and utilization level of the simulation data are both very limited. The intricacies of the vast mesomechanical response data necessitate the development and adoption of advanced data-processing methods that can gain valuable insights. To this end, this study proposed a data-mining framework that integrates a three-dimensional (3D) random aggregate method and the finite-element (FE) method for mesoscopic simulation of asphalt concrete. This framework mainly consists of two stages. In the first stage, a random aggregate method is used to establish 3D mesostructures of asphalt concrete, and FE simulations are performed on these mesostructures to model their mesomechanical responses. Based on the simulated responses, several procedures for data export, processing, and mining are developed and sequentially performed in the second stage. The data-export procedure extracts the mesomechanical responses from the FE result files and stores them into a database for efficient management. The required response data are accessed via SQL and then processed preliminarily using statistical and computational methods. Machine-learning methods and variable importance analysis techniques are used to conduct in-depth mining analyses on the processed data. The efficacy of this framework was demonstrated by applying it to investigating the effects of the volume fractions of coarse aggregates (larger than 2.36 mm) of different sizes on 129 simulated mesostructures of asphalt concrete with a nominal maximum aggregate size of 13.2 mm. The results indicated that the coarse aggregates with the particle sizes between 4.75 and 9.5 mm may make the highest contribution to the overall dynamic modulus of asphalt concrete. The coarse aggregates with larger size differences could cause more significant stress concentrations in the surrounding asphalt mortar. [ABSTRACT FROM AUTHOR]

During the production and transport of reclaimed asphalt pavement (RAP), the diffusion of recycled aged asphalt binder and virgin asphalt binder can significantly affect the mechanical properties of the virgin and aged asphalt binder system. Therefore, a thorough understanding of the diffusion behavior of virgin and aged asphalt binder system is essential for the production of RAP. In this study, a diffusion model of the virgin and aged asphalt binder system was established based on the Fick's law to calculate the complex shear modulus (|GT*|) of the system. The calculated |GT*| values were then compared with the measured values (|GD*|) obtained from the dynamic shear rheological (DSR) test. molecular dynamics (MD) simulations were also carried out to investigate the diffusion behavior of the virgin and aged asphalt binder system and to compare the simulated and calculated values of the diffusivity (D). The influence of different asphalt binder layers and saturates, aromatics, resins, and asphaltenes (SARA) on the diffusion behavior of the system was also analyzed. The results show that the |GT*| values calculated by the diffusion model are in good correlation with the |GD*| values measured by the DSR test at different temperatures and times. Furthermore, the diffusivity of virgin asphalt binder was found to be smaller than that of the four individual components, suggesting that the colloid structure and intermolecular interactions of asphalt binder play a crucial role in its diffusion behavior. Practical Applications: Asphalt pavement is a common form of pavement, but it can be seen in life that asphalt pavement often has diseases such as cracks and potholes. The cause of some pavement diseases is the decrease of the performance of asphalt binder in the pavement. Under the action of natural factors, the phenomenon that the performance of asphalt binder gradually changes with time is called asphalt aging. Therefore, if the principle of asphalt aging can be mastered, the influencing factors of asphalt aging can be clarified, and a rejuvenator that can restore the performance of aged asphalt binder to the greatest extent can be designed. It can delay the aging rate of asphalt binder and improve the durability of asphalt pavement, conversely, it can also effectively recycle and renovate old asphalt pavement, reuse waste asphalt concrete, and reduce the waste of resources. This article mainly uses molecular dynamics simulation to achieve the preceding purpose. The result is helpful in providing guidance for the production of RAP in practical application. [ABSTRACT FROM AUTHOR]

Stainless steel wires (SSWs)-modified asphalt concrete with stable long-term properties and high electrical conductivity as well as without puncturing vehicle tires is expected to become a promising multifunctional pavement material especially for solving road icing problems in cold climates. Hence, the electrical/thermal, self-heating, and self-deicing properties of SSWs-modified asphalt concrete were investigated in this study. Meanwhile, the measures for increasing the electro-thermal conversion efficiency of composites were explored. 0.75 vol% SSWs reduced the resistivity of asphalt concrete by at least eight orders of magnitude and increased the thermal conductivity by 30.38%. Preapplying a 60 V voltage instantaneously before applying voltage to utilize the breakdown effect on interface capacitors between SSWs, and employing the three-piece electrode arrangement for improving the overlapping probability of SSWs, significantly enhanced the self-heating power, peak/average temperature increase, and self-heating rate of SSWs-modified asphalt concrete by at least three times. The temperature on the top surface of SSWs-modified asphalt concrete slab (with size of 30 cm×30 cm×5 cm) under 60 V voltage increased by 24.1°C with a power density of 827.37 W/m2 for 90 min in a windless condition at −10°C. Meanwhile, the composites exhibited stable resistivity and good self-heating repeatability as well as temperature homogeneity during the self-heating process. The SSWs-modified asphalt concrete slab could melt a 4 mm ice layer within 2 h with an energy efficiency as high as 88.59% at the voltage of 60 V, and the cooling residual heat could theoretically melt a 2.4 mm ice layer to improve the self-deicing energy efficiency by 15.21%. Therefore, the low content SSWs-modified asphalt concrete exhibits promising application prospects in self-deicing pavement. [ABSTRACT FROM AUTHOR]

This study aims to design a double-gradation functional asphalt mixture considering continuous paving action and to investigate the effect of different gradation volume ratios on the mechanical behavior and functional performance of double-gradation asphalt mixture. The open graded friction course (OGFC) and asphalt concrete (AC) gradations were selected as the upper and lower layers of the double-gradation asphalt mixture. Three double-gradation volume ratios (2∶1 , 1∶1 , and 1∶2) were considered to compare the high- and low-temperature performance, water stability, permeability, and noise reduction coefficient of asphalt mixture with different gradation combinations. In addition, a discrete element numerical model based on a digital image processing technique was developed to analyze the mesoscale mechanical response and damage behavior of the double-gradation functional asphalt mixture. The research results show that the crack width and initiations of the double-gradation asphalt mixtures reduced significantly with the increasing volume percentage of AC-graded mixtures, while the larger OGFC- graded volume ratios are more conducive to functionality of the double-gradation asphalt mixtures. In addition, the volume ratio of OGFC-AC double-gradation asphalt mixture can be selected in the range between 1∶1 and 1∶2 , which can simultaneously satisfy the mechanical properties and functionality of large pore asphalt pavement. [ABSTRACT FROM AUTHOR]

The effect of moisture on the adhesion strength at the asphalt and recycled concrete aggregate (RCA) interface plays an important role in the durability performance of asphalt pavements. In this study, a universal testing machine was used to analyse the effect of moisture on the asphalt adhesion rate at the interface. Scanning electron microscopy was utilised to observe the changes in the micro-morphology of the interface before and after the effect of moisture. The effect of moisture on the interface between asphalt and recycled aggregate was investigated using molecular dynamics (MD) simulation to explore the microscopic mechanism. The results showed that the residual rate of asphalt on the surface of concrete specimens decreased from 80.2% to 34.7% after 72 h of water bath curing. The micro-morphology at the asphalt–RCA interface changed significantly before and after the action of water. Interfacial water affects the concentration distribution of asphalt components at the interface mainly by changing the nanostructure within the asphalt binder. This leads to worse adhesion properties at the asphalt–RCA interface. This study provides deeper insights into understanding water damage at the asphalt–RCA interface and provides ideas for improving the durability of the material. [ABSTRACT FROM AUTHOR]

Asphalt concrete is a foundational material in water conservancy projects, serving a critical function in the construction of impermeable structures such as dams. The seismic response characteristics and resilient safety of concrete dams are heavily influenced by the arrangement and evolution of the microscopic structure of the dam material. In this study, a high‐precision computed tomography (CT) scanning technique, in conjunction with advanced numerical simulations, was employed to analyze the internal damage and crack extension mechanism of asphalt concrete. Microstructural images of the asphalt concrete specimen were accurately captured by CT scanning, followed by the construction of corresponding numerical models. Presented simulation results show that the displacement deformation of asphalt concrete reaches its maximum value in the top region of the model and subsequently decreases with depth. Material damage was first observed at the interface between aggregate and asphalt matrix, where microcracks emerge and extend to the entire asphalt matrix, resulting in a gradual deterioration of the model performance. The simulation results indicate that the overall strength of asphalt concrete is primarily influenced by the strength characteristics of its aggregates. The stress–strain curves obtained from the numerical simulations exhibit a hyperbolic relationship, which is in high agreement with the physical test results. This study not only enhances our comprehension of the mechanical behavior of concrete but also contributes to the analysis of seismic response and risk assessment in dam engineering through dynamic experimental testing and numerical simulation. [ABSTRACT FROM AUTHOR]

The development of each nation is evaluated by its infrastructure, and each nation is competing with the others in infrastructure advancement, especially in the construction of roadways, since they play a vital role in the economic and social development of the nation. The conventional materials used for road construction are concrete and asphalt, which pose significant environmental challenges. This research gives insight into the potential of fly ash (FA) and corn stover (CS) in synthesizing geopolymer, as an alternative material for the construction of roads. This study examines the impact of three FA and CS mixture percentages and the particle size of CS on the compressive strength and porosity of geopolymer. The results indicate that incorporating larger amounts of CS in fly ash-based geopolymer may decrease the compressive strength of the geopolymer. Smaller CS particle sizes also tend to lead to lower compressive strength. Porosity of the geopolymer tended to increase with the incorporation of higher percentages of CS, particularly for smaller corn stover sizes. As a fine aggregate replacement for geopolymer, CS incorporation has the potential to reduce mined aggregate obtained from a process that harms the environment. [ABSTRACT FROM AUTHOR]

Aiming to reduce noise pollution and optimize the acoustic quality in highway tunnels, the noise characteristics on different types of pavements were analyzed and compared in this research, based on the on-site noise measurement in two tunnels with the free fields as a control group. Specifically, the noise characteristics include two aspects: various noise and noise time attenuation performance. Various noise includes on-board sound intensity (OBSI) noise and cabin noise. The noise time attenuation performance uses the indicator of reverberation time. Three types of pavements were measured, including dense-graded asphalt concrete (DAC) and single-layered and double-layered porous asphalt (PA) pavement. The results showed that, for the same type of pavement, compared with the free fields, the difference in OBSI noise in tunnels was within a range of less than 1 dBA; the cabin noise increased by 3.4 dBA~6.6 dBA. The noise level in tunnels was greater than that outside tunnels, and the longer tunnel exhibited higher traffic noise and worse noise time attenuation performances. For the same tunnel, PA pavement could reduce the cabin noise by 3.8 dBA~6.7 dBA. PA pavement also exhibited shorter reverberation time. The application of PA pavement could effectively improve the acoustic quality in the tunnel. This research contributes to noise pollution abatement and the improvement of the comfort and safety of drivers in tunnels. [ABSTRACT FROM AUTHOR]

Asphalt mixtures can include various recycled materials, which often replace some of the coarse and fine aggregate components. In some cases, a percentage of material called mineral filler, made up of particles that pass through a No. 200-sieve, is also admitted in the preparation of the mixture. With the increasing amount of packaging used as containers for various products, many of which need to be disposed of properly and become an environmental burden in warehouses without proper reuse, there is potential for including these elements in the sustainable modification of asphalt mixtures. This research suggests reusing plastic and aluminum coffee capsules, which are difficult to recycle. While most studies crush recycled materials to sizes smaller than 0.075 mm for use in mixes, this research focuses on assembling the waste capsules into a network of cells inside specimens subjected to bending to observe the mechanical behavior of the asphalt mixture. The findings indicate that incorporating capsule networks can lead to a significant enhancement in the flexural strength of the examined beams, with an increase of up to 200%. Moreover, the deformation is reduced by an average of 66% upon the emergence of the initial crack in the specimen. [ABSTRACT FROM AUTHOR]

Skid resistance of pavement plays a vital role in transportation safety, and it continuously deteriorates because the pavement was exposed to traffic and environmental loadings. Although the evaluation law of asphalt pavement skid resistance has been intensively studied, few has focused on its impact on driving safety. To close this knowledge gap, the current study used the CarSim/Simulink simulation and back-propagation (BP) neural network method to establish the relationship between pavement characteristics and vehicle driving safety. The skid resistance performances of nine types of asphalt mixture specimen were evaluated using a full life cycle dynamic friction testing machine (LCDFM), and results showed that the deterioration rate of the dynamic friction coefficient (μLCDFM) first increases rapidly, then slowly decreases and finally stabilizes. The early-stage increase resulted from the polish of asphalt film from the aggregate surface. The simulation studies indicated that driving speed exhibits the most significant impact on driving safety, followed by vehicle type, mean texture depth (MTD), and polishing time. The MTD is negatively correlated with μLCDFM , and the other factors are positively correlated. The driving safety rankings of the three pavement types and three gradations examined are open-graded friction coarse (OGFC) > stone mastic asphalt (SMA) > asphalt concrete (AC). Meanwhile, a greater value of nominal maximum aggregate size (NMAS) also induces better driving safety owing to the more abundant surface macrotexture. The research findings from this study provide reference to the materials design and pavement skid resistance prediction. [ABSTRACT FROM AUTHOR]

Model development activities are increasing in pavement research and engineering applications. At the same time, there is ambiguity and a lack of consistency with regard to checking and quantifying credibility and suitability for the intended application. Specifically, usage of the terms Verification and Validation (V&V) is seen to vary across contributions. In this context, this paper was motivated by the desire to provide a best-practice reference that underlines the significance of the V&V terms, clarifies their definition, and promotes a more unified usage. Accordingly, the objective was to offer examples that introduce the V&V jargon, demonstrate basic V&V concepts and processes, and highlight certain fine points. A total of five distinct models were introduced and discussed: (1) load-related responses in asphalt pavements, (2) load-related responses in concrete pavements, (3) crack initiation and propagation in asphalt concrete, (4) linear viscoelasticity of asphalt concrete, and (5) water flow through asphalt concrete pores. A general conclusion from this work is that successful V&V efforts are closely linked to a clear definition of the intended usage, i.e., the specific reality of interest being targeted by the model. It is also concluded that documenting V&V efforts is integral to any computational model development. Doing so communicates to potential users the region of confidence for the model alongside the expected differences with the reality of interest. [ABSTRACT FROM AUTHOR]

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

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

Featured Application: The gained knowledge can be applied by road marking material manufacturers and automotive proving ground operators to provide road marking scenarios on test tracks to test perception systems that work with camera or LiDAR sensors. The investigated method is especially useful for urban scenarios with road markings that have complex geometric shapes, such as small radii, symbols, lettering, and specific corner shapes for parking slots. In order to test camera- and LiDAR-based perception of road markings for automated driving, vehicle developers have started to utilize concepts for the agile alteration of road marking patterns on proving grounds. Road marking materials commonly used within this concept are different types of tape that can easily be applied and removed on asphalt and concrete. Due to the elasticity of tape, it cannot be used efficiently for small radii, symbols, lettering, and specific corner shapes (e.g., for parking slots). These road marking patterns are common in urban environments. With the growing capability of automated driving systems and more applications for urban environments, edgy road marking shapes gain importance for proving ground testing. This study examines the use of water-soluble road marking paint specifically designed for the use case of temporary applications on proving grounds for camera- and LiDAR-based perception testing. We found that white, water-soluble paint with 1.5% binder content and 2.25% coalescing agent content can provide realistic road markings for vehicle testing purposes. However, solubility affects the paint's vulnerability to fading during rain. Hence, renewal activities over the course of longer test drives might be necessary. The paint could be removed using water pressure without significant residue or damaging of the asphalt. [ABSTRACT FROM AUTHOR]

Designing geosynthetics for asphalt overlay is challenging due to the diversity of paving composites and paving geogrids available on the market. Challenges remains on the ideal product and tack coat to avoid debonding failure and to increase bonding quality. This research evaluates interface shear strength properties of geosynthetic-asphalt concrete specimens using seven geosynthetic interlayers tested under different tack coat rates based on asphalt retention of geosynthetics. Leutner shear tests were conducted on laboratory-prepared asphalt concrete specimens under different interface combinations. Index asphalt retention of paving geosynthetics depended on various parameters including geosynthetics type, geotextile backing, thickness and coating. The study suggests 100% of asphalt retention of the composite as design tack rate for paving geocomposites and paving geogrid composites with permanent porous fabric backing, while 220% asphalt retention as tack coat rate is suggested for geogrids. The optimum tack coat for reinforcement composites with light fabric backing falls between the optimum tack coat rates for composites and grids. The study also showed that the interface shear bond is a complex property and is not necessarily related to the fabric backing being permanent or temporary, the mass of the fabric backing, and the geosynthetics coating type and bitumen content individually. • Optimum bond coat rate depends on geosynthetic's type and properties. • Bond strength is a complex property and is related to various geosynthetic properties. • Different geosynthetics can achieve similar bond strength depending on the bond coat rate. • Bond strength depends on the bond coat rate of the whole composite, not just the fabric backing. • The optimum bond rate is between 100% and 220% of the bitumen retention of the geosynthetic. [ABSTRACT FROM AUTHOR]

This study conducted dynamic triaxial tests on a typical poured asphalt concrete material of core walls in Xinjiang, exploring the dynamic characteristics of poured asphalt concrete under various confining pressures, principal stress ratios, and vibration frequencies. On this basis, the dynamic constitutive relationship of poured asphalt concrete was investigated using the Hardin–Drnevich model. The results indicate that under different confining pressures, principal stress ratios, and vibration frequencies, the variation patterns of the backbone lines of dynamic stress-strain of poured asphalt concrete are basically identical, consistent with a hyperbolic curve. The confining pressure and principal stress ratio significantly affect the backbone line of dynamic stress-strain. By comparison, frequency has a minimal effect. The changing trends of dynamic elasticity modulus and damping ratio of poured asphalt concrete under various factors are almost the same. When the material has high dynamic stress and strain, the hysteresis loop is large. When the curve of the damping ratio becomes flat, the asymptotic constant can be used as the maximum damping ratio. The relationship between the reciprocal of the dynamic elasticity modulus and the dynamic strain of poured asphalt concrete exhibits a linear distribution. Under different ratios of confining pressure to principal stress, there are large discrepancies between the calculated values from the formula and the experimental fitting values of the maximum dynamic elasticity modulus, and the maximum relative errors reach 16.65% and 18.15%, respectively. Therefore, the expression for the maximum dynamic elasticity modulus was modified, and the calculated values using the modified formula were compared with the experimental fitting values. The relative errors are significantly reduced, and the maximum relative errors are 3.02% and 2.04%, respectively, in good agreement with the fitting values of the experimental data. The findings of this article render a theoretical basis and reference for the promotion and application of poured asphalt concrete. [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]

Porous asphalt concrete (PAC) is a low-impact medium with strong stormwater management capabilities. However, the air voids inside the PAC mixture will gradually be clogged due to sediment entering the interior of the PAC pavement in the service period. Meanwhile, the permeability of PAC pavements can be partially restored using cleaning equipment. This study investigates the changes in microscopic void characteristics of PAC under the effect of clogging and cleaning. Three kinds of PAC specimens with different void content were clogged by aeolian sand and cleaned by high-pressure water washing after complete clogging, in which the air void content, the shape parameters (roundness and aspect ratio), number, equivalent diameter, fractal dimension of air voids for the PAC mixes were quantified by X-ray computed tomography (CT) and image processing techniques before and after clogging and cleaning. Moreover, a relationship between air void microparameters and measured air void content (volume method) was established. It was found that air void shape, air void content, air void number, and equivalent diameter had a significant impact on the clogging and cleaning effect of PAC pavement, but the fractal dimension did not have a considerable impact. The migration depth of the clogging material increased gradually with the increase of air void content, and the most severe clogging was at about 10 mm from the top surface. The air void number within 1 mm increased significantly due to particle clogging. Before the construction of the road, some microscopic void parameters of PAC will be predicted from air void content measured by volume method, and combined with the results of local clogging particle size distribution, a reasonable PAC gradation will be selected to generate much larger voids than the clogging particles to improve the anticlogging performance of PAC pavement. [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]

There are many kinds of hot-mixed epoxy resins on the market with uneven performance, which makes it difficult to select the excellent performing material. This study investigated the effects of glass transition temperature (Tg) on epoxy resins, epoxy asphalts, and epoxy asphalt mixtures, aiming to confirm the Tg is an effective way to quickly select optimum epoxy resin materials. Specifically, the macromechanical properties, microproperties, and rheological properties of epoxy resins, epoxy asphalts, and epoxy asphalt mixtures were evaluated by a tensile and viscosity test, a dynamic mechanical thermal analysis test, a scanning electron microscope (SEM) test, and a dynamic shear rheometer test. Results indicate that the performances of epoxy resins, epoxy asphalts, and epoxy asphalt concretes have closely related with Tg. With Tg increasing, the tensile strength, Marshal stability, and dynamic stability are increased, while the elongation at the break, flexural tensile strains, fracture energy, and viscosity are decreased. In addition, the enhanced Tg may boost the deformation resistance of epoxy asphalts. Furthermore, the activity energy of HB, CW-HBP, and TAF is −42.86 kJ/mol , −40.79 kJ/mol , and −53.97 kJ/mol respectively, which demonstrate that Tg has no correlation with the activity energy. Besides, according to the SEM test result, the lower Tg can make epoxy resins experience ductile fracture, while higher Tg can make the HB epoxy resin experience brittle fracture. Finally, the Tg can be used to qualitatively compare and quickly select the optimum hot-mix epoxy resin used in long-span steel bridge deck pavement. [ABSTRACT FROM AUTHOR]

In order to improve the basic pavement performance of high-elastic asphalt concrete filled in the expansion longitudinal joints of seamless bridges, rubber particles and polyester fibers were added to optimize the mix proportion of elastic asphalt concrete, and the optimal asphalt–aggregate ratio was determined. The influence of rubber particles and polyester fibers on the basic pavement performance of high-elastic asphalt concrete was studied. The results show that when the dosage of polyester fiber is not more than 0.6%, the optimal asphalt–aggregate ratio is 1:5, and when it exceeds 0.6%, the optimal asphalt–aggregate ratio is 1:4. The incorporation of rubber particles reduces the compressive strength of high-elastic asphalt concrete but enhances its high-temperature stability, fracture performance, and deformation recovery ability. The incorporation of polyester fibers improves its compressive strength, high-temperature stability, fracture performance, and deformation recovery ability. In addition, the incorporation of rubber granules and polyester fibers promotes the use of green building materials and provides strong support for sustainable building practices. [ABSTRACT FROM AUTHOR]

An increasing number of asphalt concrete core wall earthen dams (ACCDs) are being constructed under complex topographical conditions. The narrow or asymmetrical river valleys might lead to significant arching effects and excessive shear deformations in the core walls, which affect structural safety. This paper focuses on the effect of valley topography on the behavior of asphalt concrete core walls in earthen dams with numerical analysis. The nonlinear behavior of asphalt concrete and rockfill materials is described using the Duncan–Zhang E–B model. The contact behavior between the core wall and transition layer is described by the Goodman contact surface model. Six parametric three-dimensional (3D) finite-element models with different valley topographies are established based on the Jiangjiakou (Bazhong City, Sichuan Province, China) ACCD and the statistical analysis of the valley topography. The effects of valley width, slope steepness, and asymmetry on the behavior of the asphalt concrete core wall are discussed. Compared with wide valleys, the stresses and displacements in the core walls in narrow valleys are relatively smaller. However, significant arching effects are observed in the upper-middle portion of the core walls. The tensile and shear stresses on both sides of the core wall in a steep-sloped valley are significantly larger than the core wall in a gentle-sloped valley. Uneven deformations are evident in the core walls in the asymmetric valley, which leads to large axial tensile strains in the core wall. [ABSTRACT FROM AUTHOR]

The development of a country is affected by various multifaceted factors, which are likely to generate the highest benefits. For example, developing water resources by constructing embankments to store water and for transportation must consider high resilience, particularly with the current challenges arising from climate change. Another factor that must be considered is the shortage of essential materials for embankment cores, such as clay, which is the primary material for constructing such cores. This study aims to analyze the stability of soil embankments between the change of materials, namely clay and asphaltic concrete, by varying the water level and increasing the embankment load. The result shows that the asphaltic concrete core exhibits a significantly higher stability than the clay core, such as its reduced water seepage and lower deformation. In the worst-case scenario, the asphalt concrete core has a thickness of 0.3 m and a seepage rate of 15.1 × 10−4 m3/day. Comparatively, the seepage rate of the clay core is approximately 10-times lower. [ABSTRACT FROM AUTHOR]