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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]

Copyright of China Mechanical Engineering is the property of Editorial Board of China Mechanical Engineering 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.)

This study investigated the performance of rubberized asphalt mixtures through Marshall and wheel track tests. The optimal binder content for rubberized asphalt specimens containing 6 and 8% rubber was determined to be 4.9 and 5%, respectively, while the control asphalt required 4.6% binder content. The results indicate that modifying the binder with crumb rubber improves the properties of the asphalt mixture. The wheel track tests show that the rubberized asphalt samples have far shallower ruts than the control samples, demonstrating successful protection against long-term distortion. Rubberized asphalt is more resistant to rutting at higher temperatures, with lower sustained strain rates and shallower ruts. Adding crumb rubber enhances the stiffness and viscosity of the asphalt binder, contributing to the improved rutting resistance of the rubberized asphalt mixtures. This study emphasized the potential of rubberized asphalt as a sustainable solution for enhancing pavement durability and longevity. The findings highlight the benefits of using rubberized asphalt in pavement engineering and provide valuable insights for optimizing binder content and improving performance. Incorporating crumb rubber in asphalt mixtures can reduce rutting and enhance the overall sustainability of pavement surfaces.

One of the main types of distress in pavement structures is rutting, which may also reduce serviceability significantly. Most design methods typically attribute rutting to the asphalt layer alone, proposing that it can be managed by controlling vertical deformation or stress at the subgrade’s top. Furthermore, these methods frequently lack precise measurements for rut depth. On-site measurements show that the majority of permanent deformation occurs in the unbound layers beneath the asphalt; attention should be directed towards these layers. In recent literature, there are calculation methods that account for accumulating strains in soils. However, further investigation is needed regarding the effect of soil properties and the significance of the pavement cross-section. The literature is also somewhat contractionary regarding the origin of permanent deformations. In this research, the residual settlement of soils (base, subbase, and subgrade) under flexible pavement systems was analyzed due to the repeated traffic loads. Rut depths were calculated and analyzed using the High-Cycle Accumulation (HCA) model. The different behaviour in each course of the pavement system is discussed to reveal their contribution to total ruts. The effect of the grain size distribution of the subgrade was analyzed, and its significance on the rutting depths was demonstrated. Standardized pavement cross-sections with different asphalt thicknesses were evaluated, and the calculated settlements of the pavement originating from the ground during the design lifetime are also presented. It is shown that, with the same number of repetitions, the settlements calculated in each traffic load class are proportional to the thickness of the asphalt course. The contribution of the base, subbase, and subgrade courses to the total settlement is also presented for different subgrade types and traffic load classes.

Despite its worldwide adoption in many countries, rubberized asphalt mixtures are not fully incorporated as an alternative paving material in current Italian road specifications. This reluctance stems from a lack of experience, resistance to change in established work practices, and, sometimes, insufficient evidence demonstrating tangible benefits with local specifications. Furthermore, conventional characterization methods such as void checks and indirect tensile strength testing by means of IDT may not accurately capture the true benefits of using alternative paving materials. This study introduces performance-driven characterization approaches with the final aim of evaluating whether more advanced procedures may provide additional information compared to current practices and, in turn, promote the use of alternative paving materials. Hence, an investigation has been conducted to compare the rutting behavior of conventional asphalt mixtures with those modified with engineered crumb rubber (ECR). This comparison utilized performance-driven characterization approaches, including a basic IDT-based methodology at higher temperatures (HT-IDT), as well as two more sophisticated approaches, the Stress Sweep Rutting (SSR) and Flow Number (FN) tests, using the asphalt mixture performance tester (AMPT). Finally, the results were compared with those obtained using the IDT, a conventional method as specified by the major Italian road authority. As a result, the addition of ECR proves beneficial in enhancing the qualities of dense mixtures tailored for use on urban and secondary roads; however, only performance-driven characterization, with both basic and advanced methodologies, can clearly describe the pivotal role of ECR in achieving discernible enhancements in the rutting behavior of asphalt mixtures. [ABSTRACT FROM AUTHOR]

As a step toward revolutionizing and optimizing freight transport, autonomous truck platooning technology (i.e., a set of connected heavy-duty trucks traveling closely at specific headway intervals) has been the center of research over last few years. Connected autonomous vehicles (CAV), in the form of truck platooning, can be implemented as a novel contribution to sustainable freight transport with the potential of offering the following synergistic benefits, among others: road safety improvements, enhanced economic prospects, and environmental preservation. In this study, the impacts of fixed-path truck platooning on pavement performance were modeled and numerically quantified using elastic and dynamic-viscoelastic finite-element (FE) methods. Factors including pavement layers' geometrical and mechanical characteristics, traffic characteristics and counts, axle configuration, and seasonal temperature are analyzed to address the platooning effect in this study. Yet, other possible wandering patterns between the fixed-path and normally distributed wandering patterns, as well as the effects of speed variations, driving behaviors, and tire pressure (i.e., variation in dynamic loading), can be further studied. The mechanical responses (namely displacements, strains, and stresses) obtained from the FE modeling were used to predict the effects of truck platooning on the pavement performance due to limited wandering (lateral movement of truck tires). The FE modeling results indicated that the channeling effects (i.e., limited tire wandering) of truck platooning have negative effects on the pavement performance with respect to decay in fatigue life and increase in permanent deformation. With fixed-path platooning, the fatigue life is reduced in the range of 13.9% to 34.5% in terms of the number of load cycles over the 20-year design life. The permanent deformation (rutting) value over a fixed period is increased by a factor of 1.2 to 2.9. [ABSTRACT FROM AUTHOR]

Geo-mat system is considered as an alternative to a flexible or rigid pavement that can be used for fire lanes, parking areas, or roadway shoulders for cars, pickup trucks, utility/delivery trucks, and fire trucks. Also, it can be used to reduce the thickness of the base course in unpaved roads. In this investigation, six cyclic loading tests were conducted to assess the efficacy of the geo-mat system on weak to intermediate subgrade layers, characterized by California Bearing Ratios (CBR) of 2%, 3%, and 4%. Control sections, consisting of a 300-mm thick base course over subgrade layers with CBR values of 2% or 4%, were compared against the test sections comprising a geo-mat system placed atop aggregates of varied thickness (150 or 50 mm) on a geotextile layer over the same subgrade layers. Each test section underwent cyclic loading, progressively increasing from 17.8 to 71.2 kN using a 300-mm diameter steel plate. The results demonstrate that the geo-mat system, particularly when placed over a 150 mm-thick aggregate base, exhibited comparable or superior performance to the control sections with a 300 mm thickness, especially under substantial cyclic loading. This was evidenced by the reduced permanent deformations beneath the loading plate and a wider load distribution. The increase of the subgrade CBR value reduced the permanent deformation significantly. When the intermediate subgrade with a 4% CBR was used, the geo-mat system played a more important role than the aggregate base and the base thickness had a minor effect on the performance. [ABSTRACT FROM AUTHOR]

In medium- to high-rise buildings, single shear walls (SSWs) are often used to resist lateral force due to wind and earthquakes. They are designed to dissipate seismic energy mainly through plastic hinge zones at the base. However, they often display large post-earthquake deformations that can give rise to many economic and safety concerns within buildings. Hence, the primary objective of this research study is to minimize residual deformations in existing SSWs located in the Western and Eastern seismic zones of Canada, thereby enhancing their resilience and self-centering capacity. To that end, four SSWs of 20 and 15 stories, located in Vancouver and Montreal, were meticulously designed and detailed per the latest Canadian standards and codes. The study assessed the impact of three innovative strengthening schemes on the seismic response of these SSWs through 2D nonlinear time history (NLTH) analysis. All three strengthening schemes involved the application of Externally Bonded Fiber Reinforced Polymer (EB-FRP) to the shear walls. Accordingly, a total of 208 NLTH analyses were conducted to assess the effectiveness of all strengthening configurations. The findings unveiled that the most efficient technique for reducing residual drift in SSWs involved applying three layers of vertical FRP sheets to the extreme edges of the wall, full FRP wrapping the walls, and full FRP wrapping of the plastic hinge zone. Nevertheless, it is noteworthy that implementing these strengthening schemes may lead to an increase in bending moment and base shear force demands within the walls. [ABSTRACT FROM AUTHOR]

Permeable pavements are vital in sustainable urban water management, addressing critical challenges while enhancing environmental resilience. This study focuses on the innovative polyurethane-bound Porous Rubber Pavement (PRP), which possesses high permeability and elasticity due to its unique composition of stone and crumb rubber aggregates with polyurethane binders. PRP's useful benefits, such as noise reduction, efficient snow/ice management, and others, enhance its appeal, emphasizing the necessity for a thorough investigation into its performance and characteristics, especially in North America. To address these gaps, this paper comprehensively analyzes PRP's durability and performance, including its strength range, failure criteria, and susceptibility to moisture-induced damage. Various testing methods are utilized, such as evaluating the abrasion loss of the stone aggregate, rutting, stripping due to moisture susceptibility, resistance to degradation from impact and abrasion, and permeability tests. This study evaluates five distinct mix compositions with varied proportions of aggregates and binders. Further, it investigates the effects of different binder types on PRP performance, such as aromatic and aliphatic binders obtained from various sources. Upon the analysis of the comprehensive test results, it was found that the mix characterized by increased rubber aggregates and a high binder content demonstrated a superior performance across various tests for PRP applications. This mix exhibited an enhanced resistance to abrasion, raveling, rutting, and permanent deformation, showcasing its durability and functionality. Additionally, when combined with an aliphatic binder, it displayed an optimal performance even in challenging freeze–thaw conditions, making it a recommended choice for long-term pavement solutions. [ABSTRACT FROM AUTHOR]

Permanent deformation is one of the failure modes considered in the analysis and design of flexible pavements. ERAPave performance prediction (PP) which is a mechanistic empirical (ME) pavement design tool utilises two distinct models for the prediction of permanent deformation in the bound and unbound granular layers including subgrade. This paper aims to calibrate these models using pavement response and performance data from accelerated pavement testing (APT) structures. Material properties such as layer modulus were established through an optimisation that involves both falling weight deflectometer (FWD) and pavement response measurements. Based on the predicted performance results, a separate set of calibration was performed for permanent deformation development in moist and wet moisture conditions. The calibrated models have resulted in predictions that are in good agreement with observed performances. Furthermore, the model parameters successfully captured the initial densification behaviour and the associated sensitivity with axle load level. [ABSTRACT FROM AUTHOR]

Many waste materials can be repurposed effectively within asphalt concrete to enhance the performance and sustainability of pavement. One of these waste materials is sawdust ash (SDA). This study explores the beneficial use of SDA as a substitute for limestone dust (LD) mineral filler in asphalt concrete. The replacement rate was 0%, 15%, 30%, 45%, and 60% by weight of total mineral filler. Scanning electron microscopy (SEM) was employed to assess the surface morphology of Sawdust (SD), SDA, and LD. In addition, a series of tests, including Marshall stability and flow, indirect tensile strength, moisture susceptibility, and repeated uniaxial loading tests, were conducted to examine the performance characteristics of asphalt mixtures of different SDA content. As per Marshall mix design, a slightly higher binder content was required for the preparation of SDA mixes. The results reveal that the asphalt mixtures prepared using SDA attain a tensile strength ratio (TSR) greater than the critical threshold, i.e., 80%, indicating the feasibility of SDA against moisture-induced damage. The highest TSR value of 87% was obtained using 45% SDA as a replacement for LD. Compared to 0% SDA, there is a reduction of 12.08% in permanent deformation for asphalt mixtures produced with 60% SDA. Also, as the SDA content increases, there is a slight improvement in the resilient modulus values, with a peak improvement of 3% at 60% SDA. In addition, the cost of producing SDA mixes was relatively lower than the control mixes, indicating the cost-effectiveness of using SDA. Overall, the study found that SDA is a promising material that can improve the performance and durability of asphalt concrete at lower production costs. [ABSTRACT FROM AUTHOR]

The importance of environmental consciousness and sustainability is increasing among transportation governing bodies worldwide. Many government bodies are concerned with maximizing the usage of recycled substances in road construction. Therefore, assessing the effect of recycled materials consumption is essential, mainly when designing new 'green' pavement types. The primary objective of this study is to investigate the impact of different treatments on improving the interfacial transition zone (ITZ) of coarse recycled concrete aggregate (CRCA) and its application in asphalt mixes. Such an aim is accomplished by enhancing its physical and mechanical characteristics, as well as its microstructure. The surface morphology, chemical composition, and intermix phases of the ITZ area and calcium silicate hydrate (CSH) compounds for CRCA were evaluated using scanning electron microscopy (SEM), an energy-dispersive X-ray analyzer (EDAX), and X-ray diffraction analysis (XRD). The performance of asphalt mixtures that included treated and untreated CRCA was also examined using different tests. It was found that heat treatment is an effective technique for enhancing the ITZ. However, cracks were seen in the mortar of CRCA when exposed to high temperatures (500 °C), which adversely affects the characteristics of the mortar. Acid treatment appeared to be an effective approach for improving the ITZ area. Nevertheless, the treatment that used acetic acid, a weak acid, was more effective than HCl acid, a strong acid. The outcomes revealed that the ITZ microstructure is significantly enhanced under different treatment types; however, microstructure improvements mainly included increased surface homogeneity and CSH compounds and a reduced Ca/Si ratio. It was also found that the asphalt mixtures with different proportions of untreated CRCA exhibited enhanced resistance to rutting. Furthermore, their tensile strength ratio (TSR) values were above the minimal level requirements. Moreover, the asphalt mixture with 30% CRCA, which was treated with various treatment methods, demonstrated a significant improvement in the mixtures' mechanical properties; therefore, its application is highly successful and an environmentally friendly solution. [ABSTRACT FROM AUTHOR]

The results of numerical simulation of perforation of monolithic and multi-layered targets are presented. The objects of study were monolithic, two-layer, three-layer and air gap targets made of steel 3. The influence of the placement of an additional layer on impact resistance in high-velocity impact (initial velocity was more than the ballistic limit of all targets) was investigated. The behavior of materials was described using a phenomenological macroscopic model of continuum mechanics. A modified Lagrangian method was used for numerical simulation of the perforation process. Test calculations were performed before numerical research. Good agreement on penetration depth of an ogival striker into a semi-infinite metal target was obtained. Numerical simulation found that impact resistance of the triple-layered target was higher than that of the double-layered target and monolithic targets. Post-perforation analysis showed the targets were completely perforated and the striker's tip was slightly eroded or blunted. Duration of perforation of all targets and damage to their materials were approximately the same, but permanent deformation of additional layers was greater with a triple-layered target. This finding can be explained by a pinching effect of additional layers acting on the striker and decelerating it. [ABSTRACT FROM AUTHOR]

Conducting and repeating large-scale cyclic load tests are challenging, as these tests are time-consuming, labour-intensive and demanding advanced laboratory facilities. As a screening test method to select the geosynthetic-reinforced pavement configurations for further investigations on a large scale, small-scale cyclic load tests by using laboratory experimental setups with lesser dimensions, therefore, are a preferred starting point for any cyclic loading tests. This paper presents the outcomes of a series of small-scale cyclic loading tests, evaluating the rutting performance of unreinforced and geogrid-reinforced unpaved roads using a circular mould with a 305 mm-diameter and 520 mm height. The test apparatus was capable of conducting a greater number of tests and provided better statistical confidence with relatively minimal effort compared to larger box tests reported in the literature. These cyclic loading tests were conducted on a granular base of varying thicknesses, placing the selected geogrid-reinforcement types (i.e. composite or biaxial) within the granular layer and/or at the base-subgrade interface. Test results show geogrid reinforcement placed at the base–subgrade interface can significantly reduce permanent-vertical deformation when the granular base thickness is relatively thin. Results also show biaxial geogrid in the middle of the granular base performs well in reducing rut depth compared with composite or biaxial geogrid placed at the base–subgrade interface. The potential benefits of geogrid reinforcement diminish with an increase in base thickness because the reinforcement acts as a rigid boundary, and failure would occur above the top layer reinforcement. Better rut resistance in unpaved granular pavements was exhibited first by double reinforcement, then biaxial geogrid at the middle of the granular base, then composite geogrid at the middle of the granular base, followed by composite geogrid at the base–subgrade interface and then biaxial geogrid at the base–subgrade interface. The findings of this experimental study are beneficial for pavement researchers in designing and planning large-scale cyclic loading laboratory or field tests for future research by optimising the number of tests, thus reducing the required amount of materials, cost and effort. [ABSTRACT FROM AUTHOR]

With the use of intelligent aggregate (IA) and discrete element method (DEM), a method was proposed to predict the influence of aggregate motion on the rutting depth in asphalt mixtures. The IAs were embedded in the center and side position of the specimen in a wheel tracking test, and the characteristics of IA motion parameters were compared with those obtained from virtual tests. The suitable motion factors for prediction model of rutting depth were first selected based on the trend of curve changes from the comparing results. Evaluation of the correlation between motion factors (Z-axis displacement and X-axis rotation angle of different IAs) and rutting depth of asphalt mixture was used to build the correlation matrix. Based on the high correlation coefficients, the curves of Z-axis displacement for No. 1 and No. 2 IA and X-axis rotation angle for No. 1 IA were further selected as the predicted factors, the prediction models of rutting depth were established. The feasibility of prediction models was verified by returning the IA motion data in indoor test and virtual test separately to observe the fitting degree between the actual curve and the prediction curve. It showed that the deviation of the prediction curve with the displacement factors was less than 4%, which was suitable to use as the predicted factors. On the other hand, due to the large fluctuation range of the rotation angle, the prediction curve with the rotation angle factor was more appropriate as a confidence curve to validate the prediction curve. [ABSTRACT FROM AUTHOR]

Permeable pavements are vital in sustainable urban water management, addressing critical challenges while enhancing environmental resilience. This study focuses on the innovative polyurethane-bound Porous Rubber Pavement (PRP), which possesses high permeability and elasticity due to its unique composition of stone and crumb rubber aggregates with polyurethane binders. PRP’s useful benefits, such as noise reduction, efficient snow/ice management, and others, enhance its appeal, emphasizing the necessity for a thorough investigation into its performance and characteristics, especially in North America. To address these gaps, this paper comprehensively analyzes PRP’s durability and performance, including its strength range, failure criteria, and susceptibility to moisture-induced damage. Various testing methods are utilized, such as evaluating the abrasion loss of the stone aggregate, rutting, stripping due to moisture susceptibility, resistance to degradation from impact and abrasion, and permeability tests. This study evaluates five distinct mix compositions with varied proportions of aggregates and binders. Further, it investigates the effects of different binder types on PRP performance, such as aromatic and aliphatic binders obtained from various sources. Upon the analysis of the comprehensive test results, it was found that the mix characterized by increased rubber aggregates and a high binder content demonstrated a superior performance across various tests for PRP applications. This mix exhibited an enhanced resistance to abrasion, raveling, rutting, and permanent deformation, showcasing its durability and functionality. Additionally, when combined with an aliphatic binder, it displayed an optimal performance even in challenging freeze–thaw conditions, making it a recommended choice for long-term pavement solutions.

Accurately predicting the permanent deformation of subgrade soils under combined loading and seasonal freeze-thaw (F-T) effects is crucial for optimizing pavement design and maintenance planning in cold regions. However, existing empirical models have limitations in capturing the non-linear deformation behavior influenced by interacting factors. This study developed a deep learning framework, specifically a convolutional neural network-bidirectional long short-term memory (CNN-BiLSTM), for time-series prediction of subgrade strains. Laboratory tests established a comprehensive database to examine soil response across various conditions. Regression analysis revealed the constraints of traditional models. The optimized hybrid architecture directly learned patterns from experimental data, outperforming regression by 29−71 % based on error metrics. Sensitivity analysis confirmed that the model identified primary governing inputs consistent with theory. Hyperparameter tuning with the Subtraction-Average-Based Optimizer further enhanced performance. This data-driven methodology demonstrated the potential of advanced machine learning in simulating complex subsurface deformation behavior under compounding factors in seasonal frozen environments.

AbstractAs a new type of engineering construction filler, it is particularly important to know the shakedown and permanent deformation characteristics of the Yellow River silt under cyclic load. In this study, a series of undrained cyclic triaxial tests for Yellow River silt are carried out by using GDS triaxial apparatus, the effects of relative density, loading frequency, confining pressure and cyclic stress ratio on the development curve of permanent strain are explored. Based on the shakedown theory and combined with the data of permanent strain development curve of Yellow River silt at different stress levels, a calculation model for its critical dynamic stress and limit cyclic stress ratio under shakedown state is determined. Further analysis is conducted on the development law of the permanent strain curve of Yellow River silt under shakedown state, and a prediction model for permanent strain of Yellow River silt considering different parameters was established. Then the accuracy of the model is verified. Combining with splitting summation method, the settlement of foundation can be calculated. [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.)

Copyright of Journal of Engineering (17264073) 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.)

Copyright of Journal of Beijing University of Technology is the property of Journal of Beijing University of Technology, Editorial Department 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 current investigation presents a comparative study on the laboratory performance of dense graded emulsion mixes prepared with 100% virgin aggregates and 100% Recycled Asphalt Pavement (RAP) with and without a rejuvenator. Waste Engine Oil (WEO) was used as the rejuvenator in the current study. Cold mix design was carried out using a slow-setting type II (SS-2) emulsion. Further, the mechanical and performance properties of various cold emulsion mixes were evaluated. The mechanical properties of cold mixes such as the Indirect Tensile Strength and Resilient Modulus were determined. Rutting and cracking performance were evaluated in terms of the dynamic creep test and indirect tensile asphalt cracking test (IDEAL-CT) respectively. It was observed that the mix prepared with 100% RAP without rejuvenator exhibited a similar rutting performance, a much higher cracking tolerance and low moisture susceptibility compared to the mix with 100% fresh aggregates. The addition of the rejuvenator resulted in improved moisture resistance and cracking tolerance of the cold mix and decreased the rut resistance. [ABSTRACT FROM AUTHOR]

Based on the confined test results and the viscoelastic constitutive model of asphalt mixtures, a three-dimensional finite element model of an asphalt pavement was established to study the effect of different working conditions on asphalt pavement. With the actual pavement structure response, a comparative analysis was conducted to assess the stress and strain experienced by the asphalt pavement under various working conditions. The results show that the asphalt pavement structure model can reflect the effect of different working conditions on asphalt pavement; the transverse stress and strain of asphalt pavement are most significantly affected by the working conditions during cornering, and the position of the maximum value is concentrated on the outer edge line of the wheel and a distance away from it; however, the longitudinal tensile stress and strain of the asphalt pavement are most significantly impacted by the working conditions of driving and braking, and the position of the maximum value is mainly distributed in the center line of the single wheel. The research results can provide a reference for the design of asphalt pavement structures. [ABSTRACT FROM AUTHOR]

Pond ash is a byproduct obtained from the combustion of coal in thermal power plants. It can be used as an alternative to conventional granular materials in compacted subgrade or subbase layers in pavements. The properties can be further enhanced by the addition of small doses of cement. Typically, the modulus parameters required for the design of pavements are based on resilient modulus models. Such models presume that the material attains a shakedown response in every loading sequence and the resilient modulus (MR) can be defined. However, it is not very clear whether a nonconventional material such as pond ash or cemented pond ash attains shakedown within 100 cycles of each sequence as stipulated in the resilient modulus test protocol. The number of loading cycles required to reach the shakedown limit is explored in this study. There are two sets of experiments conducted: the conventional resilient modulus tests with 100 cycles in each sequence and repeated load triaxial tests with 10,000 cycles for three confining pressures (41.4, 27.6, and 13.8 kPa) at a deviator stress of 69 kPa. The effect of cement dosage (2% and 3%), compaction condition (standard and modified Proctor compaction), and water content (optimum moisture content (OMC), OMC−2%, and OMC+2%) were studied. The shakedown theory is explained in terms of permanent deformation increment per cycle, dissipated energy, and tangent modulus. The resilient modulus is defined as the tangent modulus of the material which has attained shakedown. The cemented pond ash did not strongly correlate to confining pressure and hence, a constant value of the resilient modulus may be used. [ABSTRACT FROM AUTHOR]

Biomass is one the most abundant renewable energy sources, and it can be processed through different thermochemical methods to obtain oils that can replace the petroleum bitumen used in road construction. For the construction industry to accept the bitumen replacement with bio-oil, it is necessary to know its properties and determine the applicability of conventional testing methods. This research utilized a liquified wood heavy fraction (bio-oil) obtained from waste wood through an innovative thermochemical liquefaction process. The aim was to investigate a kind of bio-bitumen produced by blending this bio-oil with paving-grade bitumen. The rheological behaviour in a wide temperature range, the performance relative to fatigue cracking and permanent deformation sensitivity, and the evolution with oxidative ageing were evaluated for the bio-bitumen and paving-grade bitumens. The bio-oil significantly affected the rheological behaviour of bitumen through an overall decrease in the phase angle and by failing the time–temperature superposition principle. The strong elastic response of the bio-bitumen improved resistance to fatigue and permanent deformation accumulation; however, resistance to oxidative ageing declined. Linear viscoelastic rheological indicators proposed in the literature to assess the material's performance showed a similar trend of variation with oxidative ageing for bio-bitumen and paving-grade bitumen, though the indicators' values could not be directly compared. [ABSTRACT FROM AUTHOR]

Excess permanent deformation of subgrade may cause critical rutting in pavements, and subsurface water significantly affects the accumulation of permanent deformation. This study aims to reveal the permanent deformation behaviour of unsaturated subgrade soils. Subgrade box tests were performed at varying moisture content, stress levels and loading frequency, respectively. The test results show that the permanent deformation significantly increased with moisture content. The concept of a permitted moisture content-applied dynamic load envelope was proposed. Based on curve fitting, a prediction model of permanent deformation of subgrade soils was developed, and the effects of moisture content and loading cycles were included. The validation results show that the model exhibited reasonably good performance in modelling the deformation. This study may provide an alternative way for predicting the permanent deformation of unsaturated subgrade soils.

Geo-mat system is considered as an alternative to a flexible or rigid pavement that can be used for fire lanes, parking areas, or roadway shoulders for cars, pickup trucks, utility/delivery trucks, and fire trucks. Also, it can be used to reduce the thickness of the base course in unpaved roads. In this investigation, six cyclic loading tests were conducted to assess the efficacy of the geo-mat system on weak to intermediate subgrade layers, characterized by California Bearing Ratios (CBR) of 2%, 3%, and 4%. Control sections, consisting of a 300-mm thick base course over subgrade layers with CBR values of 2% or 4%, were compared against the test sections comprising a geo-mat system placed atop aggregates of varied thickness (150 or 50 mm) on a geotextile layer over the same subgrade layers. Each test section underwent cyclic loading, progressively increasing from 17.8 to 71.2 kN using a 300-mm diameter steel plate. The results demonstrate that the geo-mat system, particularly when placed over a 150 mm-thick aggregate base, exhibited comparable or superior performance to the control sections with a 300 mm thickness, especially under substantial cyclic loading. This was evidenced by the reduced permanent deformations beneath the loading plate and a wider load distribution. The increase of the subgrade CBR value reduced the permanent deformation significantly. When the intermediate subgrade with a 4% CBR was used, the geo-mat system played a more important role than the aggregate base and the base thickness had a minor effect on the performance.

The performance of flexible pavements is significantly impacted by the permanent deformation (rutting) of asphalt pavements. The research aims was to evaluate the permanent deformation of asphalt mixtures under different conditions. To achieve this aim, 108 cylindrical specimens have been prepared and tested under repeated loading in uniaxial compression mode. Five factors were considered in this research. They include testing temperature, loading conditions (stress level and duration), and mixture properties (bitumen type and content). The permanent deformation is evaluated in term of the following parameters, permanent micro strain εp, resilient micro strain εr, initial permanent strain (intercept, a), accumulation rate of permanent deformation (slope, b), rate of decrease in permanent deformation α and constant of proportionality between permanent and elastic strains Mu. The test results showed that the εp and a are increased as the testing temperature increased. In addition, the εp value for load duration of 0.4 s is 1.64 times the value for 0.1 s. Finally, the findings showed that the resilient response of the material is comparatively more sensitive to bitumen content than the plastic response. Furthermore, the rutting resistance is highly affected by the variables considered in this research.

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.

The objective of this research was to assess the mechanical response (resilient and plastic) of soil stabilized with petroleum asphalt concrete using asphalt emulsion under multi-stage loading. To enhance the adhesion of the asphalt film to the soil grains, the stabilized soil underwent air-drying curing for seven days. Dosage was conducted through the indirect tensile strength test using diametral compression. With the optimum content determined in the dosage (2% emulsion), additions and removals of 0.5% asphalt emulsion from this content were performed. Consequently, three specimens were molded with concentrations of 1.5%, 2%, and 2.5% of slow-setting cationic asphalt emulsion. These specimens were then subjected to drained triaxial tests under multi-stage loading, using 5 different stress pairs, totaling 50,000 cycles. Analyzing the regions defined by the total and permanent deformation curves allowed studying the plastic and elastic response, the proportionality between these regions, and the increase in elastic and plastic regions of the soil and stabilized soil in a single test, providing a more accurate interpretation. Regarding the measured deformations, as the deviator stress was increased with each loading cycle, the stabilized samples exhibited an increase in plastic deformations compared to the natural soil (control). It was also observed a proportional increase in the resilient region, indicating that the addition of asphalt made the soil less rigid but provided cohesion that was absent before stabilization. [ABSTRACT FROM AUTHOR]

Permanent deformation is the primary failure mode for the asphalt concrete (AC) pavement in urban environment. It is mainly caused by a combination of heavy traffic load, low vehicle speed and channelised traffic. A rut prediction model would therefore be a valuable tool for planning maintenance scheduling and selecting an appropriate asphalt material. This study uses the PEDRO (Permanent deformation in asphalt concrete layers for roads) model to evaluate the rutting performance of flexible pavements in dedicated bus lanes and intersections in urban areas. For this purpose, three road sections along a bus lane in Malmö, Sweden, were selected. To achieve this, AC cores from the road sections were tested using a Shear Box Tester to characterise the asphalt mixtures. Traffic data such as axle load, tyre configuration, speed, and lateral wander distribution of vehicles, and climate data were measured for the selected sections. Field measurements were carried out to assess the structural conditions of the pavements and to measure transverse profiles. This study introduced a procedure for the evaluation and local calibration of the PEDRO rutting model. The results revealed that the prediction of the transverse profiles are generally in good agreement with the rut measurements. [ABSTRACT FROM AUTHOR]

X-ray computed tomography (CT) as a non-destructive testing method has been used to evaluate the air voids and void-related distresses in asphalt mixtures. To evaluate the air void development in asphalt mixtures under loading, this study proposed a volume-equivalent maximal ball model based on CT to characterise the changes of void connectivity. The void distribution and shape features were described using the variation coefficient of modified annular-sector segmentation, positional eccentricity ratio, and sphericity. The results indicate that voids are relatively heterogeneous and discrete in stone mastic asphalt (SMA-13) mixture compared with dense-graded asphalt concrete (AC-13), particularly for those with volume smaller than 0.01 mm3. The void connectivity and distribution in SMA-13 seem to be more susceptible to load as its coarse aggregates tend to shift their positions during deformation. Rutting reduces the vertical inhomogeneity of AC-13 but increases that of SMA-13. Moreover, loading complicates the void geometry of AC-13 whereas the opposite is true for SMA-13, foreboding that SMA mixtures maintain the potential to resist rutting failure after 1 h of loading compared to AC types. In general, the topological characteristics of air voids within asphalt mixtures and their dynamic response during permanent deformation are principally dependent on mixture gradations. [ABSTRACT FROM AUTHOR]

Crushed waste rocks (CWR) are widely used to build mine haul roads. However, the permanent deformation in waste rocks layers can result in surface rutting. Realistic prediction of pavement rutting requires models that can accurately capture the permanent deformation behaviour under repeated loading. However, such models are usually based on advanced laboratory apparatus such as multistage (MS) repeated load triaxial (RLT) tests. In this study, a new approach, using MS repeated load California Bearing Ratio (RLCBR) tests, was proposed to estimate the permanent deformation behaviour of CWR. MS RLCBR tests are faster, easier and more often available than MS RLT tests. A series of MS RLCBR and MS RLT tests for different stress levels were therefore carried out on the same material to characterise CWR permanent deformation behaviour. Results showed that Rahman and Erlingsson model that modified by time hardening approach could satisfactorily capture CWR permanent deformation behaviour for MS RLT tests. A new model was proposed and fitted on MS RLCBR test results to predict CWR permanent deformation behaviour. This model performed well in describing MS RLCBR test results and predicting the CWR permanent deformation behaviour. Results indicate that MS RLCBR tests could be an effective alternative to MS RLT tests for estimating the permanent deformation behaviour of CWR. [ABSTRACT FROM AUTHOR]

This study evaluated the influence of asphalt binder and biochar-based geopolymer composites on the permanent deformation resistance (PDR) of asphalt concrete. The influence of three design variations, asphalt binder, biochar, and geopolymer content, was evaluated by employing the response surface method (RSM) based on the Box Behnken approach. The asphalt binder content ranged between 4 and 6%, whereas the biochar and geopolymer content ranged between 0 and 4%. The average rut depth of Bio-Geopolymer Asphalt concrete (BGAC) was employed as the response variable. The synergetic influence of the design variable was examined using the RSM approach, and a model was developed to determine optimum contents for improving PDR. The model has very high R2 values and adequate precision, showing that there is a significant relationship between the experimental and predicted values. The study ANOVA revealed that the asphalt binder and a biochar-based geopolymer composite modifier showed a significant effect in enhancing the PDR of BGAC. Furthermore, the optimization shows that the optimal content for biochar, geopolymer, and asphalt binder are 3.22%, 1.81%, and 5.4%, respectively. The generated model's percentage error was found to be 5%, showing a significant correlation between the actual and predicted data. The results of this study show that using RSM to predict and optimize the PDR of BGAC is a very efficient and effective technique. [ABSTRACT FROM AUTHOR]

In this study, permanent deformation potential of different asphalt mixtures subjected to the same aging condition was assessed, based on viscoelastic characteristics from the dynamic modulus (DM) test. First it was shown that the HWTT and RLPD test results were not well correlated, which might be due to the differences in the boundary condition and the impacts of moisture damage and stripping in the HWTT. The analysis results suggested that the shape parameter (γ) of the DM master-curves could be utilized to assess the rutting resistance potential of the asphalt mixtures from the RLPD test, compared to other rheological parameters such as the inflection point frequency and β. The |E*| at the RLPD test condition was well correlated to the rutting performance compared to the asphalt mixture's rutting parameter |E*|/sinδ and the |E*| at the inflection point frequency. A novel rutting parameter (VERIndex) was developed to assess the rutting resistance potential of the asphalt mixtures, which simultaneously accounts for the |E*| and slope of the DM master-curves. Thereafter, the cracking and rutting performance thresholds were proposed, and, correspondingly used in the performance space diagram to aid with implementing the balanced mix design approach using the viscoelastic characteristics of asphalt mixtures. [ABSTRACT FROM AUTHOR]

Conventional asphalt has been used along the time with relatively satisfactory performance. However better performance in terms of development, environment, and economic benefits needs to be addressed. Asphalt binder modification has been one of the most common methods to improve the performance of bitumen over time. The objective of this study is to provide insight into the modification of asphalt binders to reduce thermal cycling by introducing Aerogel. Several tests were conducted including Softening Point (SP), Rotational Viscosity (RV), Dynamic Shear Modulus (G*), Multiple Stress Creep Recovery (MSCR), Flexural Creep Stiffness (BBR), Binder Bond Strength (BBS), and Thermal Conductivity (TC) tests. The response of five aerogel products was assessed based on performance. The outcomes of this study were encouraging and promising. Thermal resistance properties and cost per kilogram of each product were used to determine the more suitable aerogel product for further utilisation. The addition of aerogel reduced the susceptibility to damaging thermal effects of bitumen, reducing the permanent deformation and thermal cracking potential. However, the implementation of aerogel in binder must be enhanced to overcome the workability and safety concerns, which restrict the feasibility of its usage. [ABSTRACT FROM AUTHOR]

This paper presents experimental results of laboratory model tests of geosynthetic reinforced highway base layers subjected to repeated loads. The potential benefit of geocell and geogrid, when used in the base layer as a reinforcement material, was examined and assessed by performance indicators including total, permanent (plastic), and elastic (resilient) deformation, traffic benefit ratio (TBR), rut depth reduction (RDR), percentage of elastic deformation, and resilient modulus (MR). In the light of the results of this study, geocell and geogrid-reinforced bases outperform the unreinforced base in terms of elastic and permanent deformations. Further experimental results reveal that although the thickness of the base layer was decreased to a rate of 33%, geocell and geogrid enable a considerable reduction in the rut depth at an approximate rate of 21% and 13%, respectively. Moreover, when the thickness of the base layer remains constant, about 48% to 43% reduction in the rut depth was provided by geocell and geogrid reinforcement. [ABSTRACT FROM AUTHOR]

In general, granular fill materials are widely used to construct new pavement and rehabilitate old pavement. For pavement design, it is essential to know the basic characteristics, such as the permanent deformation behavior of these materials. Considering this phenomenon, this study aims to explain the performance of granular fill layers in pavement systems using cyclic plate load tests. For this purpose, a large-scale cyclic plate load test facility, also known as pavement model testing (PMT), was developed to investigate the permanent deformation characteristics of the pavement structure. To conduct experiments, a standard pavement structure was built with granular fill layers on top of a soft clay subgrade and a geotextile between the subgrade and the base layer. The PMT was used to apply a 40 kN cyclic load through a steel plate with a 305 mm diameter for up to 10,000 cycles after the pavement structure was built. A total of four tests were carried out to evaluate the effects of the granular fill layer's thickness on the pavement's permanent deformation. Furthermore, an analytical solution was developed for the fill layer thickness using the test results. Additionally, the outcomes of some previous studies in the literature were compared to the ones that were obtained. The results of this study indicate that the permanent deformations of the pavement structure and the subgrade increased with the number of load cycles. The permanent deformations began to limit at 3000 cycles when the fill layer thickness was 20 cm, but it was observed that deformations did not limit at 3000 cycles when the fill layer thickness increased to 45 cm. Also, the permanent deformations decreased by two times when the granular fill layer thickness doubled appropriately. [ABSTRACT FROM AUTHOR]

Premature failure in asphalt concrete pavement has been the main concern for pavement construction companies and engineers in recent years because of the large rise in traffic volume and loads and the temperature extremes in the summer and winter. The use of modifiers in asphalt concrete mixtures has attracted much attention to increase the performance and lifespan of pavements. As nanotechnology developed, several researchers concentrated on how these materials can help increase pavement serviceability by minimizing rutting and moisture damage. This study evaluates the Hydrated Lime (HL) effect by two methods (wet and dry hydrated lime) on the durability of the warm mix asphalt. The first method, HL, has been supplemented to the asphalt binder with three ratios (0.5%, 1%, and 1.5%) by weight of asphalt (Wet HL). Then, the second method was added via the aggregate weight as a replacement filler using three percentages (1%, 2%, and 3%) (Dry HL). The mechanical qualities, including Marshall Mix design, moisture susceptibility, and permanent deformation, were evaluated through experimental tests. Results showed that the mechanical characteristics and the fineness of the HL particle sizes are positively correlated.

Permanent deformation in asphalt concrete pavements is pervasive distress [1], influenced by various factors such as environmental conditions, traffic loading, and mixture properties. A meticulous investigation into these factors has been conducted, yielding a robust dataset from uniaxial repeated load tests on 108 asphalt concrete samples. Each sample underwent systematic evaluation under varied test temperatures, loading conditions, and mixture properties, ensuring the data's comprehensiveness and reliability. The materials used, sourced locally, were selected to enhance the studyʼs relevance to pavement constructions in hot climate areas, considering different asphalt cement grades and contents to understand material variability effects on deformation. The detailed dataset created from the experimental program acts as a pivotal resource for refining predictive models and optimizing asphalt concrete mixtures and pavement design strategies, aimed at improving pavement performance and longevity under diverse operational and environmental conditions.

Based on the confined test results and the viscoelastic constitutive model of asphalt mixtures, a three-dimensional finite element model of an asphalt pavement was established to study the effect of different working conditions on asphalt pavement. With the actual pavement structure response, a comparative analysis was conducted to assess the stress and strain experienced by the asphalt pavement under various working conditions. The results show that the asphalt pavement structure model can reflect the effect of different working conditions on asphalt pavement; the transverse stress and strain of asphalt pavement are most significantly affected by the working conditions during cornering, and the position of the maximum value is concentrated on the outer edge line of the wheel and a distance away from it; however, the longitudinal tensile stress and strain of the asphalt pavement are most significantly impacted by the working conditions of driving and braking, and the position of the maximum value is mainly distributed in the center line of the single wheel. The research results can provide a reference for the design of asphalt pavement structures.