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The availability of high-quality aggregate for infrastructure development in Canada has significantly decreased. This reduction has posed significant challenges, particularly in large urban areas across Canada. Moreover, exploring the potential of incorporating innovative by-products into pavement structures has displayed potential advantages in technical, economic, and environmental aspects. The methodology presented in this paper is based on several research projects from over the past twenty years. This case study is based on the several research projects that have been conducted at the Centre for Pavement and Transportation Technology (CPATT) in Canada. The focus of this paper is developing a framework that can be used to evaluate the use of recycled materials in asphalt pavement. These include recycled concrete aggregate (RCA); recycled asphalt roof shingles (RAS); recycled crumb rubber (RCR); and recycled asphalt roof shingles (RAS) in asphalt pavement. In addition, the use of RCA in concrete pavement will also be evaluated. In addition, the use of RCA in concrete pavement will also be evaluated. A methodology and strategy for implementing these materials and designs into specifications, while also managing risk, are outlined. Finally, the work presents a life cycle assessment analysis, including the analysis of cost and sustainability. Overall, the paper illustrates the process of evaluating products, technologies, and designs from technical, economic, and environmental viewpoints, and then implementing them in a robustly engineered way. Generally, the collected data results from the lab, field performance of the test sites, and sustainability and Life Cycle Cost Assessment (LCCA) analyses are very promising. For example, the Hot Mix Asphalt (HMA) pavement design with a 40% RAP was the most environmentally friendly. Meanwhile, it was determined that the HMA mix comprising 20% RAP and 20% Crumb Rubber Modifier (CRM) was found to be the most creative and environmentally friendly option. According to another study, higher storage durations were shown to improve RAP and virgin binders' blending, thereby raising the general quality of HMA and RAP mixtures. Furthermore, the study discovered that mixtures containing various types of untreated CRCA in different amounts had higher Indirect Tensile Strength (ITS), rutting resistance, and stiffness modulus than the control mix, which contained 0% coarse recycled concrete aggregate (CRCA). This suggests that the effective utilization of recycled materials is a viable approach with the capacity to significantly enhance the adoption of recycled components in asphalt pavements. [ABSTRACT FROM AUTHOR]

Semirigid pavements are gaining importance in the pavement design field due to their improved performance in freezing zones. These semirigid pavements are constructed similarly to asphalt pavements, but with a cement-stabilized base layer. However, there is a limited study that quantifies the influence of design factors on the performance of semirigid pavements. Therefore, an attempt was made to investigate the role of subgrade, temperature, moisture, traffic, crack joint spacing, speed, asphalt thickness, cement-treated base (CTB) layer thickness, elastic modulus, and modulus of rupture of CTB layer on semirigid pavement design. Different combinations of factors were formulated using fractional factorial design in the design of the experiment (DoE). All factors influencing the design of semirigid pavements were considered on two levels (low and high). This analysis used data from the Federal Highway Administration's (FHWA's) Long-Term Pavement Performance Program (LTPP). These data were incorporated into the AASHTOWare Pavement ME Design 2.6.1 (MEPDG) software. Design-Expert was used to determine the significance of various factors on the performance indexes. In addition, an optimization technique was used to determine the optimal design thickness for cement-treated base under various subgrade and climatic conditions. The result suggests that the thickness of a CTB layer is greater on fine-grained soil than on coarse-grained soil. [ABSTRACT FROM AUTHOR]

Top-down cracking (TDC) is recognized as a significant form of distress in asphalt pavements. While the NCHRP project 1-52 introduced a mechanistic-empirical (ME) predictive model for TDC, this model was found to be less accurate in certain traffic conditions—overpredicting crack initiation in sections with medium to low traffic and underpredicting in high-traffic sections. To enhance the precision of TDC predictions, a new fracture-mechanics-based framework has been developed. This improved framework employs a Hot Mix Asphalt (HMA) fracture mechanics methodology, resulting in a marked enhancement in the accuracy of predicting crack initiation times when compared to the original sub-model from NCHRP 1-52. The new framework also incorporates a novel aging model for the asphalt mixture, ensuring more precise inputs for the crack propagation model. The propagation prediction sub-model has been refined by implementing a J-integral-based Paris' law developed in the NCHRP 1-52 project. The efficacy of this updated framework was rigorously tested on eighteen diverse pavement sections across various geographic locations, with well-documented performance history and material properties. The outcomes indicate that the predicted initiation and propagation of TDC closely align with actual field observations, demonstrating the robustness and improved reliability of the new model. [ABSTRACT FROM AUTHOR]

This study aimed to propose a framework for sustainable assessment of pavement by the integration of LCA and LCCA methods. Additionally, a tool was developed that employs a multi-criteria decision-making process to determine the most sustainable pavement design alternative. The developed tool was applied in a case study involving 496 weighing modes to assess the impact of different maintenance intervention levels and the discount and traffic growth rates on the sustainability of design alternatives with varying maintenance treatments. The results of the analysis revealed that asphalt pavement with a stabilised base demonstrated superior sustainability, covering over 87% of the weight modes. Conversely, concrete pavement exhibited lower sustainability, representing only 6.5% of the weight modes. Additionally, among maintenance activities, preventive treatments exhibited heightened sustainability in scenarios with higher discount rates and lower traffic growth. These findings highlighted the importance of selecting the appropriate pavement type for sustainable infrastructure development. [ABSTRACT FROM AUTHOR]

Accurate estimation of traffic load plays a crucial role in the economical design of pavements. The cross sectional distribution of the vehicle positions means that the traffic load is spread across the surface of the pavement. Several factors influence the distribution of vehicle positions and hence load. When wheel paths are perfectly aligned with each other, this is termed channelised traffic (or channelisation). This study investigated the impact of channelisation on asphalt pavement rutting. Data was collected on 100 sections of pavement in the city of Portsmouth, United Kingdom including vehicle/wheel positions and rut depths. Regression analysis was conducted to understand how the degree of channelisation influenced the rut depths that the traffic loading had created. The analyses revealed that the degree of channelisation of traffic has a statistically significant contribution to the progress of rutting. In this study, the difference between the maximum and minimum degrees of channelisation observed, related to a seven-fold difference in the rut depth. These findings give further guidance to pavement engineers when designing new pavements and considering the maintenance schedules for existing pavements, as it allows them to better predict the future condition and lifespan of a pavement. [ABSTRACT FROM AUTHOR]

The cooling performance of heat reflective coatings (HRC) for pavement applications has attracted wide attention. In this study, the cooling performance and bond strength of HRC were investigated and the attenuation pattern associated with the skid resistance of specimens sprayed with different amounts of HRC coating was examined based on four-wheel wear test. Furthermore, an asymptotic model associated with the attenuation of the HRC's skid resistance was developed for investigating the effects of anti-slip particle gradation and dosage as well as HRC dosage on the skid resistance. The results show that the cooling performance and bond strength of HRC (sprayed amount: 0.8 kg/m2) are 12.4 °C and 1.75 MPa, respectively, and the skid resistance of HRC sprayed with different amounts of HRC was stabilised at approximately 48 BPN after 150,000 abrasion cycles. The attenuation pattern of the skid resistance of the skid-resistant HRC (SHRC) fitted well with the developed asymptotic model, showing a correlation coefficient exceeding 0.99 and an error of less than 5% from the test value. Anti-slip particle gradation (G4), anti-slip particle dosage (0.6 kg/m2) and HRC dosage (0.6 kg/m2) were selected based on the stable value of the skid resistance, and SHRC was developed for pavement applications. [ABSTRACT FROM AUTHOR]

The properties and service life of asphalt pavement are to a large extent dependent on pavement structure. Most pavement structural designs at home and abroad commonly follow the typical structural design method; however, considering that the geographical span from east to west in Inner Mongolia is large, a single pavement structure cannot be optimal for all environments, and low-temperature fracturing may easily occur during the road service life. Ten kinds of pavement structures are analyzed in this paper. The pavement structure mechanical indices are analyzed using different soil base modulus values, different axle loads, and different internal contact conditions. A low-temperature return period was introduced to establish a Gumbel extreme temperature model. The low-temperature protection index and calculation method based on the return period for asphalt pavement is proposed, which takes Arxan City as a benchmark for calculating low-temperature protection values in Eastern Inner Mongolia. The low-temperature fracturing formula is improved to calculate low-temperature indexes for different pavement structures. Using a life cycle cost model, the economy of different pavement structures is evaluated from the aspects of initial cost, maintenance cost, and pavement residual value. By establishing a combined weight-fuzzy pavement evaluation model and combining the mechanical response, low-temperature fractures during the return period, and economy of the life cycle, a comprehensive property ranking for different pavement structures was obtained. Finally, the typical structural combination for the asphalt pavement in the Eastern Inner Mongolia is recommended to be three layers of asphalt surface + semi-rigid base or three layers of asphalt surface + asphalt treated base (ATB) + semi-rigid base. [ABSTRACT FROM AUTHOR]

For the characteristics of semi-rigid base asphalt pavement prone to cracking, various stress-absorption layers are applied widely by decreasing stress concentration, improving interlayer bonding and waterproofing. Existing studies on the anti-cracking effect of stress absorbing layers rarely consider top-down fatigue cracking on the outside of the boundary of the vehicle loading zone. Firstly, this paper proposes a finite element model setting a downward expansion of fatigue crack in pavement based on fracture mechanics. The influence law of modulus and thickness of stress absorbing layer on stress intensity factor of crack tip and the fatigue life of the pavement is analyzed furthermore. Numerical calculation results demonstrate that shearing stress intensity factor increases with stress absorbing layer thickness and decreases with stress absorbing layer modulus, while fatigue life of pavement grows with the modulus of the stress absorbing layer and decreases with its thickness. Sensitivity analysis indicates that the modulus of the stress absorbing layer has a greater effect on the fatigue life of the pavement relative to thickness, which offers reference for further promotion and application of stress absorbing layer. [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.)

Copyright of Guangdong Architecture Civil Engineering is the property of Guangdong Architecture Civil Engineering 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.)

Construction and demolition waste (CDW) materials account for a considerable part of waste materials throughout the world. As these materials are not usually recycled, reusing them in construction projects is of major significance. In this study, recycled concrete, bricks, and glass were used as 100% aggregates of chip seal, which is a corrective or preventive pavement maintenance method. A cationic rapid setting (CRS-2) bitumen emulsion was also used to prepare the chip seal. Different tests, including the sand patch test, sweep test, British pendulum tester (BPT), interface bond, and Vialit test, were conducted. The results of these tests revealed that all these materials had sufficient aggregate embedment for vehicle speeds of more than 70 km/h, and the number of chips was less than 10%, indicating their good performance. All developed chip seals ranked as high skid resistance pavement at ambient temperature. The chip seals developed with concrete and glass showed the best adhesion with an asphalt pavement surface and an aggregate–bitumen adhesion at very cold and ambient temperatures due to the fact of their chemical compositions. Overall, using concrete aggregates to develop chip seals under different traffic loads is recommended. Finally, these findings can provide a novel approach for recycling CDW materials with low costs. [ABSTRACT FROM AUTHOR]

The low-altitude technology of unmanned airborne infrared detection system is used to effectively monitor the temperature segregation in the paving stage and realize the temperature uniformity control of asphalt pavement construction. The image mosaic method can splice two images with overlapping areas together to form a panoramic image. In order to solve the problems of long time-consuming and low accuracy of aerial image mosaic algorithm, the low-temperature area of the whole pavement can be obtained quickly and accurately. In this paper, threshold segmentation technology is introduced to convert the image captured by the unmanned aerial vehicle (UAV) into a binary greyscale image so as to compensate for the mosaic error caused by temperature difference. In order to improve the efficiency and accuracy of splicing, a reference plate is used, which can provide enough feature points for splicing. Finally, the image mosaic method proposed in this paper can quickly obtain the image of the whole low-temperature area of the newly paved asphalt pavement, which has practical value and positive significance for the quality control of asphalt pavement. [ABSTRACT FROM AUTHOR]

Concrete structures cannot efficiently perform their functions over time due to chemical and physical external effects. Thus, enhancing the relationship between repair and aged structures, and also improving the durability properties of concrete is crucial in terms of sustainability. However, high costs, negative environmental effects, and incompatibility problems occur in repair/retrofit applications. Furthermore, three-quarters of the failures in the repaired/retrofitted structures are caused by a lack of repair durability. The need for repair in pavement/bridge decks is also frequently encountered, and early-age performance problems with repair materials cause pavement/bridge decks to be unavailable for certain periods of time. Engineered Cementitious Composite (ECC) can be effectively used as repair/retrofit and pavement/bridge deck material. It also has a minimal need for repair/retrofit thanks to its high durability properties. This article presents state-of-the-art research regarding the application of ECC as a repair/retrofit and pavement/bridge deck material. Studies in the literature show that the repair/retrofit properties of ECC outperform conventional concrete and steel fiber-reinforced concrete. ECC can be a solution to high early strength and drying shrinkage problems frequently encountered in the use of repair materials. It could also be used for different repair applications such as cast, sprayed, and trenchless rehabilitation. Moreover, ECC might fulfill specific requirements for pavement, pavement overlay, tunnel pavement, airfield pavement, and bridge deck. These superior performances are attributed to ECC's kink-crack trapping mechanism, uniquely large inelastic strain capacity, strain hardening, high tensile strain capacity, and multiple microcracking and ductile behaviors, especially bonding behavior and self-healing. [ABSTRACT FROM AUTHOR]

The Urban Heat Island (UHI) phenomenon is commonly solved by implementing materials with optimal thermic and evapotranspiration properties which help decreasing the air temperature in dense urban areas. This approach has been applied in this study, testing six different materials (replacing the current Macadam) in one parking area in Bari (Italy), which provides a large-scale testbed, by means of a thermal three-dimensional non-hydrostatic simulation: impervious asphalt pavement (IAP), asphalt permeable pavement (APP), green pavement (GP), green pavement-asphalt permeable pavement (GP+APP), grey porous concrete blocks (GCB), and light concrete permeable pavement (LCPP). The highest-performance pavements in terms of potential air temperature (PAT) reduction were the GP (−1.22°C), GCB (−1.26°C) and LCPP (−1.22°C), which also showed a constant relative humidity, suggesting their UHI mitigation benefits. A comparison of the structural properties as well as the construction and maintenance costs of such pavements is also provided, finding the best mitigation strategy (GCB). [ABSTRACT FROM AUTHOR]

In order to study the interlayer shear behavior of bridge deck pavement, a numerical simulation was conducted to analyze the influence of varying interfacial conditions on shear stress at the bottom of pavement layers under the moving loading effect. Moreover, the shear strength of the different adhesive and waterproof adhesive materials was evaluated by conducting laboratory tests. The results showed that improving the bonding condition at the upper interlayer led to the reduction of the shear stress at the bottom of the pavement layers. With the increase of the friction coefficient of the upper interface to the full bonding state, the resulting shear stress at the bottom of the upper layer declined to the lowest value, which was about 35% of that of the full slip state. When the lower interlayer was in the full slip or partial bonding state, the resulting shear stress at the bottom of the lower layer decreased linearly with the increase of the friction coefficient of the upper interlayer. Moreover, once the contact state of the upper interlayer reached the full bonding state, the resulting shear stress at the bottom of the lower layer reached the minimum, which is about 88% of that of the full slip state. To improve the integrity and shear resistance of the bridge deck pavement structure, interlayer bonding should be strengthened. In this regard, the resin emulsified asphalt was determined as an appropriate adhesive material to be applied at the upper and lower interlayers. In addition, interlayer shear bond strength, regardless of the type of adhesive materials, was decreased with increasing temperature. Finally, statistical analysis results indicated that all factors of structure type, type of adhesive material, and temperature statistically have a significant effect on interlayer bond strength. The findings of this study could provide a theoretical basis and experimental support for improving the interlayer design and construction in the concrete bridge deck pavement structure. [ABSTRACT FROM AUTHOR]

Thermal power plants in India produce a large quantity of fly ash, which is harmful to the environment. Underutilization of fly ash and the scarcity of natural minerals have created the need for an unusual construction strategy to prevent huge waste dumps on valuable land and to preserve fast-depleting resources. A study was conducted to determine the efficacy of lime-stabilized fly ash blended with quarry fines as flexible pavement subbase materials. The laboratory investigations were conducted to determine compaction characteristics, unconfined compressive strength, California bearing ratio (CBR), and durability to obtain the optimal quarry fines, fly ash, and lime (QFL) mix. The durability of QFL mixes was studied using 12 wetting–drying cycles. Using the strength and durability criteria specified by the Indian Road Congress, the optimum mix proportion of 40Q:60F+3L was determined. Pavement analyses were performed using the IITPAVE program. The QFL mix was observed to be superior to conventional granular subbase (GSB) layer material in terms of service life and cost-effectiveness. A field investigation was carried out on trial test sections constructed using the optimum QFL mix and GSB in the subbase layer of pavement. Field dry density and dynamic cone penetrometer (DCP) tests were performed on the compacted subgrade and subbase layers to assess the desired quality assurance in the construction of test sections. The early structural performance assessment of pavement sections using a falling weight deflectometer (FWD) test indicated that QFL could effectively replace conventional GSB. [ABSTRACT FROM AUTHOR]

• We comprehensively analyze various factors affecting pavement condition index (PCI) • We identify the important determinant features for building PCI prediction models. • We develop a new FCM-XGBoost modelling framework to effectively predict the PCI. Predicting Pavement Condition Index (PCI) is crucial for identifying potential pavement distresses and developing effective pavement maintenance strategies. Here, a new Fuzzy C-Means-eXtreme Gradient Boosting (FCM-XGBoost) PCI prediction system is developed. First, asphalt pavement sections and concrete pavement sections are distinguished, and the Fuzzy C-Means (FCM) clustering algorithm is employed to cluster the asphalt and concrete expressway sections respectively based on multiple factors influencing PCI. Next, an eXtreme Gradient Boosting (XGBoost) model is trained for each cluster of expressway sections. Finally, in the system application stage, the PCI of an expressway section for the next year is predicted using the XGBoost model trained for the specific cluster that the expressway section belongs to. Validation results based on actual pavement condition data indicate that the proposed FCM-XGBoost PCI prediction system can achieve slightly higher accuracy compared with several high performance benchmark models, which include the Random Forest model, the Gradient Boosting Decision Tree model, the Light Gradient Boosting Machine model and the XGBoost model. The developed PCI prediction system contributes to the improvement of PCI prediction approaches and can be potentially applied in deploying effective and cost-efficient pavement maintenance strategies. [ABSTRACT FROM AUTHOR]

An investigative study was carried out on the assessment of engineering properties of asphaltic concrete used for pavement construction in Akwa Ibom State, South-south, Nigeria. A total of 225 compacted samples of wearing course asphaltic concrete were obtained from three different asphalt plants in Eket, Oron and Uyo designated as D, E, and G, respectively. The test results based on the outcome of the Marshal Stability for the three different asphalt plants ranged from 7.51-13.36 kN, 9.36-11.34 kN and 8.26-9.46 kN with corresponding flow values which ranged from 3.33-3.94 mm, 2.40-3.48 mm and 2.73-3.19 mm for asphalt plants D, E, and G, respectively. The test outcomes revealed that a good number of the test samples were within the benchmark of the Nigeria General Specifications for roads. Three predictive models were built for the estimation of Marshall Stability for the three different sites. Based on the outcome of t-test (paired two sample for means) and analysis of variance (ANOVA) single factor, there was no significant difference between the experimented values and model formulated results. Also, the formulated model yielded an excellent coefficient of determination (R2) of 0.9513, 0.9777 and 0.9777 for the three sites. This excellent coefficient of determination reflect the models could be used in prediction of stability strength. The correlation statistic and their respective p-values of each of the independent variables, BIT, VIM and VFB has shown to contribute more than the other variables in building the established models and thus expedient in forecasting the performance of asphalt pavements. [ABSTRACT FROM AUTHOR]

Airports strive to prevent safety issues, such as foreign object debris (FOD), by pavement management using the pavement condition index (PCI). The index is used in decision-making processes for overall pavement maintenance and repair, such as the prevention of additional damage due to cracks and the like. However, considering the current situation in Korea where mostly mid-sized and large commercial airports exist, problems regarding direct applications of the existing PCI deduct value have been consistently pointed out. In addition, as the relationship between the PCI and whether maintenance and repair are required is unrealistic, there have been difficulties in communication between maintenance and repair staff and decision makers. Therefore, to resolve these problems, this study first analyzed the calculation procedure of the existing PCI and then redefined the main distress type of Korean airport pavements. In addition, a deduct value curve (DVC) in terms of the severity level for six main distress factors of asphalt pavements and eight main distress factors of concrete pavements and a corrected deduct value curve (CDVC) for multiple distresses in terms of the pavement form were developed using panel rating, which is an engineering approach, by forming an airport pavement expert panel. Finally, a Korea airport pavement condition index (KPCI) was proposed using the curves, and the field application results were compared against the existing PCI to examine the adequacy of the KPCI. As a result, the developed criteria showed an overall trend lower than existing PCI. Moreover, it was verified that this trend increases with worsening pavement condition. It appears that a more discriminating evaluation may be possible when determining pavement conditions by PCI results of the developed criteria. [ABSTRACT FROM AUTHOR]

Considering the future shortage of natural aggregates, various researchers have promoted the recycling of by-products into various asphalt pavement types. This paper promoted a double-recycling technique, where thermally treated waste silt was used as a filler for the bituminous skeleton and grouting material of a geopolymer-based semiflexible pavement. Semiflexible pavements (SFP) inherit the flexibility of common asphalt pavements and simultaneously benefit from the rigidity of cement concrete pavements. For this purpose, waste silt obtained from a local asphalt plant was thermally treated at 750 °C and was used as the filler to produce the porous skeleton. Two different materials, including conventional cement-based and a geopolymer-based cement, were used as the grouting material. The geopolymer grout was produced by mixing metakaolin (MK), potassium-based liquid hardener and calcined silt as filler. The porous and grouted samples were characterized in terms of indirect tensile strength (ITS), the indirect tensile strength modulus (ITSM) and moisture sensitivity. The use of thermally treated waste silt as filler in porous asphalt demonstrated promising results and was comparable to the control samples produced with limestone as the filler. However, the control samples grouted with cement-based material outperformed the geopolymer grout in all aspects. Moreover, the addition of calcined silt improved the low-temperature fatigue performance of porous and grouted asphalt pavements. [ABSTRACT FROM AUTHOR]

Concrete pavement proportions are increasing in Korean expressways, resulting in increased maintenance cost. The length of degenerate concrete pavements that have exceeded the design life (20 years) was 1150 km in 2015 and 2605 km in 2020 and is expected to rapidly increase. To extend the service life of concrete pavements, life-cycle cost (LCC) analysis was conducted on asphalt and concrete overlays, based on the different maintenance methods. LCC analysis was performed when the shoulder was used and when it was not used between 6000 and 35,000 AADT traffic according to the two-lane and four-lane traffic. During overlay, one lane was completely blocked, and the value per vehicle was converted into the user cost using the Construction Analysis for Pavement Rehabilitation Strategies software, according to whether the shoulder was used to maintain the number of lanes. In addition, LCC analysis was conducted by examining the construction cost and life-cycle according to each overlay method. When the shoulder was used, the total construction cost decreased, owing to the reduction in user cost, indicating that the implementation of the traffic measure of using the road shoulder improves user satisfaction and cost. The asphalt overlay was observed to be more favorable than concrete overlay in terms of the initial total construction cost. However, under a 20-year cycle, the economic efficiency of concrete overlay was higher than that of asphalt overlay. After repairing the deteriorated target sections of concrete pavements, the overlay method (asphalt or concrete) ought to be selected according to the target service life for beneficial economic effect. Concrete overlay was to obtain about 20% or greater LCC effect compared to asphalt overlay, and at least 5% or more additional LCC effect obtained when the shoulder was used. [ABSTRACT FROM AUTHOR]

This paper studies the effect of various parameters on the effective thermal conductivity (λeff) of the geothermal pavement system when constructed using construction and demolition (C&D) materials. Recycled asphalt pavement (RAP) and recycled concrete aggregates (RCA) were utilized to experimentally model the geothermal pavement system, consisting of copper tubes to circulate water in the pavement and harness thermal energy. Numerical computational fluid dynamics (CFD) and discrete element method (DEM) methods were used to simulate the geothermal pavement system. Six samples of RAP and RCA aggregates with different particle size distributions were utilized to study the effect of important parameters in the geothermal pavement system. According to the results, coupled CFD-DEM approach could simulate the heat transfer mechanism in geothermal pavement compared to the results of the CFD simulation. The results indicated that increasing porosity would decrease λeff. The decrease rate depended on the gravel content of the sample where samples with a higher gravel content experienced a higher rate of decrease. Also, simulation results showed that increasing the gravel content could increase the value of λeff. Increasing the axial stress resulted in an increase in the value of coordination number (CN) and λeff. Moreover, comparing the thermal power and contact distributions indicated that the morphology of the heat conduction was the same as the contact network distribution. To study the effect of the particle shape on λeff, a novel approach was used that comprised of 3D scanning and printing real particle shape of RCA aggregates by thermochromic material. Simulated assemblies with DEM were verified using 3D printed particles. The effect of aspect ratio (AR) on λeff was studied which indicated that increasing AR would increase λeff. Decreasing AR to one, on the other hand, increased the time needed to reach the steady state. [ABSTRACT FROM AUTHOR]

Continuous friction measurement equipment (CFME) has been demonstrated as an appropriate method to acquire friction around the critical slip ratio for the Pavement Friction Management (PFM) programme. Through a comprehensive field data collection on testing sites with different preventive maintenance (PM) treatments, this study assessed the influences of various characteristics on the CFME measurements. Field friction data were collected by a Grip Tester, one type of CFME, and the corresponding texture profiles were acquired by a high speed texture profiler. For each testing site, friction data was measured under nine operational conditions with three water film depths and three testing speeds. An adaptive signal processing technique, Hilbert-Huang Transformation (HHT), was applied to extract amplitude and instantaneous frequency of profiles as the texture parameters. Subsequently, the HHT texture parameters, along with pavement conditions and testing operational characteristics, were deployed as the influencing factors for the development of statistical friction model. The results reveal that the CFME measurements are most sensitive to the change of water film depth and pavement surface texture properties. This study is anticipated to gain a better understanding of the characteristics of CFME measurements and implement CMFE to support PFM programme effectively. [ABSTRACT FROM AUTHOR]

Due to its superior properties, usage of Roller Compacted Concrete (RCC) in pavement applications gradually increases. As the compaction effort and curing conditions applied are significantly altered between laboratory and field conditions, performance of RCC may be considerably different. Therefore, studies that are carried out to compare the laboratory and field RCC performance have crucial importance. On the other hand, number of these studies are very limited. In the presented study, a RCC mixture was designed and applied to a site in Kocaeli/Turkey. Required pavement thickness was determined based on AASHTO (1993) design methodology, and performance of laboratory and field RCC (in terms of compressive strength, splitting tensile strength, ultrasonic pulse velocity (UPV), capillarity, abrasion resistance, density, water absorption and porosity) were determined and compared. As a result of the study for almost all of the performance parameters decreased values were obtained for RCC when compared to laboratory specimens. This result was attributed to difference between field and laboratory compaction effort and curing conditions. [ABSTRACT FROM AUTHOR]

From the perspective of sustainable waste management and its environmental impact, waste biomass bottom ash (BA) remains problematic and challenging to use as a recycling material for civil engineering infrastructures. This study evaluated the performance of lateritic soil (LS), stabilized with cement and biomass BA, as a subbase material. BA has been considered a replacement material in LS prior to the introduction of hydraulic cement stabilization means. The geotechnical engineering tests comprised the modified Proctor test, the California Bearing Ratio (CBR) test, and the unconfined compression test. X-ray fluorescence (XRF) and X-ray diffraction (XRD) tests were conducted to investigate the mineralogical properties of the stabilized soil samples. The leachate test was performed with a permeability mold to measure the release of heavy metals. Finally, the benefits of using the stabilized subbase material were assessed using the mechanistic–empirical (M–E) pavement design approach. Based on the results obtained, the strength and stiffness characteristics of the stabilized soils indicate that the efficiency of the mix satisfied the Thailand highway specification. The admixture of 80% BA and 5% cement is suggested for use as a soil–cement subbase material for flexible pavements, due to its good engineering and environmental properties. The results of the M–E design demonstrate the effectiveness of the stabilized soil presented herein. The study's outcomes are predicted to promote the utilization of waste BA as a promising pavement material. [ABSTRACT FROM AUTHOR]

It is widely admitted that the repeated passage of heavy goods vehicles as well as environmental conditions are the main causes of damage to road structures. This sometimes requires the use of rehabilitation techniques to maintain the road in operational and safe condition and extend its life. The current trend in the world is to find new low cost materials that are able to guarantee the best performance of pavements; the Roller Compacted Concrete (RCC) is a good example. This work is mainly concerned with the use of more rigid local materials in the construction of roads and their placement by compaction instead of flexible asphalt concrete wearing courses which have been shown several drawbacks. Indeed, flexible asphalt concrete wearing courses become softer under heavy traffic and require a very expensive bituminous material supply. It is therefore urgent today to find cost-efficient road construction techniques that can combine durability and hardness. The strategy used in this research consists, on the one hand, in making a roller compacted concrete made of recycled aggregates using materials from local deposits with a low dosage of cement, and on the other hand, to validate this study numerically by evaluating the maximum compressive strength and then to model the cracked sections of roller compacted concrete containing recycled aggregates in order to develop a new method that allow minimizing the degradation of pavements. This would certainly make the present research paper more original. The results obtained allowed to find that it is quite possible to manufacture roller compacted concrete with partial incorporation of recycled aggregates with compressive strength acceptable and approximately equal to 34 MPa at 28 days. This type of RCC is more resistant and less dangerous because recycled aggregates improve the behavior of pavements, especially in the presence of cracks where we found that the stress intensity factor for RCC with natural aggregates (− 1.1631 MPa√m) is greater than in RCC with recycled aggregates (− 0.4989 Mpa√m). [ABSTRACT FROM AUTHOR]

In Korea, the transverse tining method has been applied to the surface texture of concrete pavements as it provides excellent skid resistance that improves road safety. However, transverse tining produces higher noise levels of about 4–5 dB(A) compared to asphalt pavements. Accordingly, exposed aggregate concrete pavement (EACP) is introduced since the low tyre-pavement noise and long-term skid resistance can be obtained. Surface texture of this pavement consists of coarse aggregates that are exposed after the removal of the cement mortar. Tyre-pavement noise in EACP resembles that in asphalt pavement due to the similar surface texture that is characterised by wavelength. This parameter is the distance between aggregate particles; thus, it is significantly related to the size and amount of coarse aggregate in the mixture proportion. In addition, short wavelength tends to produce low tyre-pavement noise and this can be a criterion to minimise the noise level in pavement design. Therefore, this study aims to optimise the mixture proportion of low-noise EACP based on the requirement of surface texture and structural capacity. As a result, concrete mixture with 8-mm size and 27% amount of coarse aggregate provided as short-wavelength as asphalt pavement and adequate structural strength was also achieved. [ABSTRACT FROM AUTHOR]

In order to comprehensively analyze the dynamic response of full-depth asphalt pavement under moving load, a three-dimensional model of pavement structure and dynamic load moving zone are established based on ABAQUS finite element software. Based on the time history curves of different structures, the stress-strain states at the bottom of each structural layer in different structures under moving load are analyzed. The results show that the stress, strain, and shear stress of the middle layer of full-depth pavement are smaller than those of semirigid base pavement, and rutting is closely related to the deformation of this layer. The dynamic response results of the same structure at different speeds are similar, but the increase of the maximum speed will increase the shear stress at the bottom of the layer, and the road is more prone to longitudinal crack. [ABSTRACT FROM AUTHOR]

Many roads in hot regions of the world are exposed to very high temperatures especially in desert areas during the summer season, where the temperature could reach more than sixty Celsius degrees. Temperature variations cause a lot of distress in flexible and rigid pavement such as rutting, vertical transverse (i.e., thermal) cracking, thermal fatigue damage, blow up/buckling, in addition to generating warping stresses. Accurate detection of the surface temperature of flexible pavement is very important for pavement design analysis. This research presents a new model to estimate the temperature of flexible pavement layers under extremely high temperatures as a set of simultaneous equations. The proposed model included Clear-Sky as sub-model to estimate the solar energy of beam and diffuse radiation of the pavement surface. Ambient temperature was calculated by solving the model depending on the time of the day. The proposed model was validated via experimental data collected from one-year measurements at instrumented pavement section in New Sohag, Egypt. The asphalt surface temperatures were measured for summer, winter solstices and vernal and autumnal equinoxes. It was found that the model provides reasonable estimates compared to the experimental data. The proposed model is deemed appropriate for estimating pavement layers temperature in hot regions. [ABSTRACT FROM AUTHOR]

Permeable interlocking concrete pavements (PICP) are being used increasingly in stormwater management. A 2-year experimental study was conducted to quantify some uncertain parameters related to PICP. The study entailed the hydraulic testing of a representative volume of PICP within a specially constructed Infiltration Table Apparatus with a surface area of 10 m2, and able to be tilted up to 6°. The study aimed to address some of the controls of infiltration into, and flow through PICP by investigating the effect of the selected construction materials and the incline of the pavements. Based on the permeability data gained on PICP, it was verified that both the choice of construction materials (in both the layer works and the sand used for fill between the bricks) and the incline of the pavements were found to affect their hydraulic properties. In general, the selection of lower permeability materials in a PICP surface layer, and/or increasing the incline, decrease the overall permeability of the pavement. [ABSTRACT FROM AUTHOR]

The granular layer, being the major structural component in low-volume roads, exhibits significant plasticity and undergoes both elastic and permanent deformation under repeated vehicular loading. Stress-dependent, nonlinear resilient moduli, as well as elastoplastic models, have been considered for characterizing individual pavement materials; however, very limited research is available that studies the composite behavior of granular material and subgrade soil in two-layered pavement structures. In the present study, a single-lane low-volume road was considered and critical pavement responses, that is, surface and interface deformations, and interface stresses were examined for different modular ratios and pavement thickness–tire width ratios. The elastoplastic Drucker–Prager model was considered in a finite-element analysis for simulating both the elastic and plastic aspects of granular materials. The results indicated that elastoplastic characterization of the granular layer and multiple-wheel loads made a significant difference in the responses of pavements with thin granular layers and low modulus ratios; however, its influence reduces with increases in the thickness of the granular layer at a constant modulus ratio. For a constant pavement thickness, relatively greater deformations were obtained at higher modulus ratios, which indicated that pavement responses depended on the composite behavior of the pavement system rather than the strength of an individual layer. Based on the variation in deformations and interface stresses with the modulus ratios and pavement thickness–tire width ratios, prediction models were developed that can be utilized for predicting surface and interface deformations, and interface stresses for the analysis and design of a two-layered pavement structure. [ABSTRACT FROM AUTHOR]

Geogrid reinforcement effectively controls the rutting of pavements under traffic loads, especially when constructed over soft subgrades. In this study, extensive large-scale model pavement experiments (LSMPEs) were performed to quantify the rut depths of flexible pavements. In all, 20 LSMPEs were performed on pavement sections overlying subgrades of different strengths with California bearing ratio (CBR) values varying from 1% to 5%. Three geogrid types were considered to study the effects of material type [polypropylene (PP) and polyester (PET)] and tensile strengths (30–60 kN/m) on the rutting behavior of flexible pavements. LSMPEs were first performed under monotonic loading to obtain the optimum depth of reinforcement within the base layer of flexible pavement. Thereafter, a series of repetitive load (haversine loading) was applied on paved sections of reinforced flexible pavements using a high-end, linear, double-acting actuator system. Rut deformations were measured at both the surface and the subgrade levels of the model pavements. The rut deformations were found to distinctly vary in accordance with the condition of the subgrade, the thickness of the pavement layers, and the type of geogrid used. The rut depth reduction (RDR) at the pavement surface was found to range from 22% to 69% for PP- and PET-geogrid reinforced base layers. Geogrid reinforcement significantly reduced the rut depths at the subgrade level (as high as 90%) compared to unreinforced sections. In addition, the model pavements were instrumented with the earth pressure cells to measure the vertical pressures transferred to the subgrade due to surface loading. The ability of geogrid reinforcement to distribute loads to wider areas was quantified in terms of the vertical stress distribution angle, αmax , at the end of the load cycles (N=100,000 cycles). The αmax maximum values for geogrid (GG1/GG2/GG3)-reinforced pavements built over weak subgrade (CBR=1%) varied from 28.4° to 32.2°, while it was 25.7° for unreinforced pavements. Likewise, αmax values for geogrid-reinforced pavements overlying a relatively fair subgrade (CBR=5%) varied from 34.5° to 43.6° against 30.4° for an unreinforced case. [ABSTRACT FROM AUTHOR]

Warm-mixed reclaimed asphalt pavement technology, as an environmental recycling method to reuse waste materials, has been widely investigated around the world. However, the skeleton of the reclaimed asphalt mixture is unstable due to the existence of the reclaimed materials. Semiflexible pavement has been successfully used in heavy traffic area due to its high rutting resistance. For combination with these two methods, a warm-mixed reclaimed semiflexible pavement material was proposed in this study. In order to investigate the interfacial weakening effect of the warm-mixed reclaimed semiflexible pavement material in a microstructural perspective, an image-based two-dimensional microstructural finite element model was presented. Results show that the maximum compressive stress of the new and RAP aggregates and cement mortar with interface is greater than that without interface and the compressive stress of the material increases when considering the interface. Besides, the maximum compressive strain of the material with interface is greater than that without interface and the strain values in the models with interface at all three positions are greater than those without interface. [ABSTRACT FROM AUTHOR]

Purpose: As an ambitious strategy of national interest in China and with an aim at achieving the 'one-hour economic circle' among Greater Bay Area cities by 2035, the Guangdong-Hong Kong-Macao Greater Bay Area has been transformed into a world-class bay economic belt in South China. Consequently, the large-scale construction of transportation infrastructure inevitably resulted in the consumption of a lot of resources and significant environmental impact. Such a scenario could produce conflicts with Greater Bay Area's commitment on the sustainable development goal, such as China' carbon intensity reduction. Methods: In this study, the environmental impacts caused by highway pavement in Greater Bay Area at urban agglomeration level were quantified through life cycle assessment method, measured by greenhouse gas emissions (CO2eq). Results and discussion: Our results show that the total emissions resulted from the use of materials during the construction of highway pavement, its maintenance, and rehabilitation phases in Greater Bay Area reached 4.4 (± 0.25) million tonnes CO2eq in 2018, of which material phase (material production and transportation to the construction site) accounted for more than 70% of the total impact. The construction phase of asphalt pavement is larger than the maintenance and rehabilitation phase, while the maintenance and rehabilitation phase of cement concrete pavement is larger than the construction phase. Moreover, a scenario-based analysis implies that the continuing growth of highway mileage in Greater Bay Area will accelerate the environmental impact till 2035. Conclusions: These findings can help understand the impacts of highway pavement in Greater Bay Area and provide useful support for policy-makers. In addition, the methods are useful for the quantification of greenhouse gas emissions of highway construction on city level in China and beyond. [ABSTRACT FROM AUTHOR]

Pavement segregation usually cause engineering quality problems such as early damage of asphalt pavement. Therefore, it is of great significance to carry out segregation detection in the construction process. However, existing image detection technology has two problems: 1) the segregation boundary and the index are not clear; 2) the segregation assessment is localized. In order to find useful solutions to these two problems, this study proposed an Aggregation Segregation Generative Adversarial Network (AG-GAN) to generate virtual pavement images with segregation failure. Moreover, a multi-scale fusion method of Recurrent Neural Network (RNN) and the Global Averaging Sliding Window (GASW) algorithm is developed to achieve globalized aggregation evaluations. Based on extensive experiments tests, conclusions obtained that the accuracy rate of re-current neural network for segregation determination of pavement sequence can be up to 84.62%. In addition, automatically assessment of the segregation condition of pavement section can be achieved, which proves the practical application effectiveness of the proposed algorithm in the actual paving process. [Display omitted] [ABSTRACT FROM AUTHOR]

Precast concrete pavement (PCP) has proven itself to be one of the most efficient methods for repair and replacement of concrete pavement, as well as for construction of new pavement in the areas of heavy traffic. The application of PCP ensures fast construction of concrete pavement without compromising the quality of concrete. This paper provides a brief of various types of PCP that have been used worldwide and their application in the repair of damaged pavement, continuous construction of pavement, Airfield application and temporary pavement construction. It further discusses critical aspects of PCP that require careful analysis prior to its field implementation. The paper specially focuses on panel dimensioning, load transfer mechanism, lifting arrangement, stacking arrangement, transportation and base preparation for PCP. Suitability of different types of PCP for varying site conditions has been discussed. Innovative developments related to PCP and the future scope of this technology have also been discussed. [ABSTRACT FROM AUTHOR]

The restricted use of reclaimed asphalt pavement (RAP) in hot mix asphalt (HMA) motivates the use of RAP in portland cement concrete (PCC) as an aggregate replacement. The addition of RAP causes significant changes in PCC's properties, but little research has been done to investigate the impact of these changes on pavement performances. In this study, punchout performances of continuously reinforced concrete pavement (CRCP) made with PCC containing RAP (RAP-PCC) slabs were extensively assessed using existing models in the Pavement ME. Based on the results, the major drawback for using RAP in CRCP is the RAP-PCC's reduced modulus of rupture (MOR); the reduced MOR causes higher stress to strength ratio in the slab, which can lead to higher chances of fatigue. However, the RAP-PCC slab is anticipated to have tighter transverse cracks due to the reduction in modulus of elasticity. A decrease in crack width could potentially yield a higher transverse crack load transfer efficiency (LTE). The Pavement ME simulations indicate that the CRCP made with RAP-PCC, which has tighter cracks, can maintain a higher LTE for a much longer time and ultimately leads to a longer pavement service life compared to the plain CRCP. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the effect of multi-wheel loading gear configuration on loading-induced failure potential of airfield flexible pavements. Field response testing was conducted in the National Airport Pavement Test Facility (NAPTF) using different multi-wheel gear configurations. Three-dimensional (3-D) finite element (FE) models were developed to simulate multi-wheel loading along with non-uniform tyre contact stresses. The 3-D FE models were validated by tensile strains measured from response testing. The effects of wheel loading configurations and magnitudes on different strains responses were compared for two pavement sections with different asphalt layer thicknesses. Analysis results showed that six-wheel gear configuration caused the greater pavement responses. The critical shear strains were found greater than critical tensile strains at the same loading condition and pavement structure, especially for thick asphalt pavements. This is consistent with top-down cracks observed at field sections after traffic testing. On the other hand, shear strains increase more rapidly as the load level increases as compared to tensile strains; while thin asphalt layer is more sensitive to loading magnitude as compared to thick asphalt layer. The multi-wheel effect on fatigue life is more significant for thick pavement due to the load superposition effect under different wheels. [ABSTRACT FROM AUTHOR]

The rehabilitation process of asphalt pavements using the technique of milling and filling can cause several environmental problems due to either the disposal of the milled asphalt mix or the exploration of natural resources. One alternative to mitigate these impacts is to reuse this milled material, known as reclaimed asphalt pavement (RAP), in the construction of new pavement layers. Within the several available techniques to reuse the RAP, cold recycling using an emulsified asphalt-recycling agent has shown great potential. The aim of this study is to evaluate the application of a cold recycled asphalt mix using 100% RAP with an emulsified asphalt-recycling agent as a new pavement base course. A trial section was built employing this material as a pavement base course in a heavy traffic highway in Brazil, and its structural behavior was monitored for 12 months using a Falling Weight Deflectometer (FWD) to assess its performance over time. Furthermore, a laboratory-testing program was performed to evaluate the recycled mixture stiffness and strength through resilient modulus and indirect tensile strength tests. These tests were used to investigate the influence of the storage interval (7, 14, and 28 days) considering the time between mixing and compaction of the mixture. The effect of the curing time after compaction (1, 3, 7, 26, and 56 days) was also assessed. It was verified in laboratory and in the trial section that the stiffness increases with curing time. Furthermore, the backcalculated elastic resilient moduli indicated values in the same order of magnitude to those obtained in the laboratory tests. In addition to the laboratory test findings, it was also observed that the longer the period of storage, the higher the values of stiffness and tensile strength for short periods of curing. This behavior was not verified when longer curing periods were used. In general, the use of cold recycled asphalt mixtures as base course of new pavements proved to be a promising alternative to reuse RAP. [ABSTRACT FROM AUTHOR]

As part of developing a safe, efficient, and sustainable transportation infrastructure, health monitoring of pavements and bridges, as well as the monitoring of real-time roadway conditions for safety, have become increasingly important. The sensors, data acquisition, and data transmission equipment needed for such monitoring require electricity that is often unavailable, in short supply, unreliable, or a combination of the three. The development of a more robust and capable health and safety monitoring equipment will be greatly facilitated by a more ample, reliable source of electricity than is currently available. This investigation explores the concept of using pavements as thermoelectric generators to produce and supply electricity, using the temperature differential that exists between a pavement's surface and its underlying layers. A thermoelectric module was placed within a hot-mix asphalt pavement system and a Portland cement concrete pavement system in the laboratory and subjected to full-spectrum lights. The amount of electricity generated was measured, and the results indicated that electricity can be generated. Initial power generation suggests that one square meter pavement surface area may be capable of providing about 62000 microwatts, enough power for 620 wireless transmitters and the accompanying sensor. It is estimated that it may be possible to produce up to 300 W/lane-km. [ABSTRACT FROM AUTHOR]

Traditional permeable pavements are constructed with rigid aggregates and have low load-bearing capacity. The crack development due to loads and unpredicted ground movements reduces their service life. The widespread cracks on the surface of conventional asphalt accelerate the pavement structure deterioration and reduce the overall service life. In this research, the end-of-life tyre products shredded to tyre-derived aggregates (TDAs) were utilised along with crushed rock (CR) in different fractions of a porous structure to enhance the flexibility of permeable pavement whilst maintaining the minimum load-bearing capacity for use in footpath and low-volume roads. The transitional behaviour from a semi-rigid structure owing to the rigidity of CR aggregates to a more flexible structure for mixtures at higher TDA content was investigated. The impact of rigid-rigid and flexible-rigid inter-particular contacts at low and high stress levels is investigated. The plastic and recoverable deformations of the flexible-rigid blends under monotonic and repeated loadings are compared. Also, the impact of polyurethane binder content on improving the mixtures flexural strength is investigated. The lightly bonded flexible-rigid mixtures are a viable replacements for traditional porous pavements to improve the load-bearing mechanism and increase the flexibility of pavement. [ABSTRACT FROM AUTHOR]

It was noted that the durability of asphalt concrete pavements is determined by the time of the trunk road cracks formation. Developed by the authors previously the theory of the cracks propagation in heterosystems [1] has allowed to investigate the problem of the cracks propagation in the rubber-bitumen composite. This investigation shows that it is necessary to use very small (150-750 nm) rubber particles in the asphalt binder to ensure optimal high durability of pavement. [ABSTRACT FROM AUTHOR]

Recycling of asphalt has become a well-established practice in many countries, however the road pavement industry remains a bulk consumer of extracted raw materials. Novel solutions that find root in circular economy concepts and life-cycle approaches are needed in order to enable optimisation of infrastructure resource efficiency, starting from the design stage and spanning the whole value chain in the construction sector. Itis within this framework that the present study presents a full-scale validation of asphalt mixtures specifically designed to ensure durability of flexible road pavements and at the same time enabling the reuse of reclaimed asphalt pavement (RAP) through the incorporation of bio-materials as recycling agent. These bio-recycled asphalt mixtures have been first designed in laboratory and subsequently validated in a real scale experiment conducted at the accelerated pavement testing facilities at IFSTTAR. Four pavement sections were evaluated: three test sections with innovative bio-materials, and a reference section with a conventional, high modulus asphalt mix (EME2). Two tests were realized: a rutting test and a fatigue test and for each of them the evolution of bio-recycled asphalt mixtures properties as well as the pavement deteriorations were recorded and studied. Evolution of the bio-asphalt mixtures was monitored for a 5 months period after paving by a bespoke nondestructive micro-coring, extracting and recovering methodology developed at the Western Research Institute (WRI). The structural health of the pavement sections was monitored through periodic falling weight deflectometer (FWD) as well as with strain gages and temperature sensors. As a result the three tailored bio-asphalt mixtures performed similarly or better than the control mixture, both in terms of property evolutions and durability. [ABSTRACT FROM AUTHOR]