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Abstract: The objective of this study was to analyze the accumulated effects of leaching in two test roads were municipal solid waste incineration (MSWI) bottom ash and aggregate from a railway embankment, respectively, were used as subbase aggregates. Solid samples from the subbase and the subgrade were collected in trenches, which were excavated perpendicular to the road extension. The samples were analyzed with respect to pH, water content, electrical conductivity and extractable fractions of macro and trace constituents. To conclude, spatial distribution patterns of different constituents in subbase and subgrade layers confirms the existence of two major transport processes in a road with permeable shoulders: diffusion underneath surface asphalt layers driven by a concentration gradient directed horizontally towards the shoulder of the road where the dissolved elements are carried away by advection. [Copyright &y& Elsevier]

The Structural Health Monitoring (SHM) of pavement infrastructures holds paramount significance in the assessment and prognostication of the remaining service life of roadways. In response to this imperative, a methodology for surveilling the surface and internal mechanical responses of pavements was devised through the amalgamation of Accelerated Pavement Testing (APT) and Falling Weight Deflectometer (FWD) examinations. An experimental road segment, characterized by a conventional asphalt pavement structure with semi-rigid bases, was meticulously established in Jiangsu, China. Considering nine distinct influencing factors, including loading speed, loading weight, and temperature, innovative buried and layout configurations for Resistive Sensors and Fiber-optic Bragg Grating (FBG) sensors were devised. These configurations facilitated the comprehensive assessment of stress and strain within the road structure across diverse APT conditions. The methodology encompassed the formulation of response baselines, the conversion of electrical signals to stress and strain signals, and the proposition of a signal processing approach involving partial filtering and noise reduction. In experimental findings, the asphalt bottom layer was observed to undergo alternate tensile strains under dynamic loads (the peak strain was ten με). Simultaneously, the horizontal transverse sensor exhibited compressive strains peaking at 66.5 με. The horizontal longitudinal strain within the base and subbase ranged between 3 and 5 με, with the base registering a higher strain value than the subbase. When subjected to FWD, the sensor indicated a diminishing peak pulse signal, with the most pronounced peak response occurring when the load plate was situated atop the sensor. In summary, a comprehensive suite of monitoring schemes for road structures has been formulated, delineating guidelines for the deployment of road sensors and facilitating sustained performance observation over extended durations. [ABSTRACT FROM AUTHOR]

Bridges and pavements are two major infrastructure components of a transportation network providing mobility of freight and commodities for economic vitality and access to a range of users as social benefits. However, the lack of a comprehensive infrastructure management system incorporating bridges and pavements inhibits accurate performance prediction, optimal maintenance actions, and the associated use of shrinking budgets. This paper presents an integrated probabilistic life-cycle connectivity framework for the performance analysis of transportation networks containing bridges and asphalt pavements by considering flexural and shear failure modes for prestressed concrete and steel bridges and four failure modes, including international roughness index, rut depth, alligator cracking, and transverse cracking, for asphalt pavements. In this framework, neural network–based deep learning models are used to assess the probabilistic performance of transportation networks and to provide guidance for the associated maintenance strategies. An existing transportation network consisting of bridges and asphalt pavement segments is selected to investigate its life-cycle connectivity reliability and component importance using the matrix-based system reliability method. Results show that the consideration of asphalt pavement failure probability has a significant effect on the probability of transportation network connectivity. [ABSTRACT FROM AUTHOR]

Interface bonding conditions are important to ensure the desired performance of multi-layered asphalt pavements. Most previous studies only investigated the sole effect of the interface at a specific location, although the most extreme case is when poor bonding occurred at multiple locations simultaneously. Also, the sensitivity of bonding effects to structural parameters is unclear. Therefore, this study investigated the effects of multiple bonding scenarios and structural parameters on critical responses, the 3-D viscoelastic finite element model. The results indicated that critical locations for cracking potential depend on bonding scenarios. Interface bonding between asphalt and aggregate base layers mainly contributed to bottom-up cracking, while the interface between asphalt layers was more associated with top-down and near-surface cracking. In addition, the use of a thicker asphalt layer was more effective than the use of a strong base layer to mitigate the negative effects of poor bonding conditions. [ABSTRACT FROM AUTHOR]

For analysis, design, and rehabilitation purposes of flexible pavements, the temperature profile of asphalt layers should be determined. The predictive models as an alternative to in-situ measurements, are rapid and easy methods to determine the temperature of asphalt layer at various depths. These models are developed based on limited field data. Hence, there is a need for developing new models for prediction of temperature profile of asphalt layers in various climatic regions. In this study, climatic data was retrieved from the Long-Term Pavement Performance (LTPP) database. The information of 33 asphalt pavement test sections in 16 states in the United States was employed for calibrating the predictive models. Using the prepared data, the temperature profile of asphalt layers was predicted utilizing four regression-based models, including Ramadhan and Wahhab, Hassan et al., Albayati and Alani, and Park et al. models. Existing prediction models were calibrated, and to predict the temperature profile of asphalt layer, new models were developed. Performance evaluation and validation of newly developed models showed an excellent correlation between predicted and measured values. Results show the ability of the developed models in predicting the temperature profile of asphalt layers with very good prediction precision (R2 = 0.94) and low bias. [ABSTRACT FROM AUTHOR]

Purpose: Using typical structure of asphalt pavement in Harbin area of China, and the formula of generalized friction coefficient between base and surface layers of asphalt pavement in cold area is established. Design/methodology/approach: Through structural characteristics analysis of asphalt pavement in cold area, the generalized formula of friction coefficient between base and surface layers of asphalt pavement in cold area is derived. The formula can quickly calculate the friction coefficient between layers of asphalt pavement. Findings: Based on quantitative analysis to the contacting state between layers of asphalt pavement in cold area, the relationships between generalized friction coefficient and resilient modulus of asphalt mixtures, temperature shrinkage coefficient and temperature have been established. Originality/value: The findings can enrich the description methods about the contacting state between layers of asphalt pavement, and have a certain theoretical and practical value. Through the application of the formula of generalized friction coefficient between layers, it can provide a technical basis for the asphalt pavement design, construction and maintenance in cold area. [ABSTRACT FROM AUTHOR]

It is widely recognized that reliability-based optimization methodologies are rational and promising tools to perform the life-cycle management (LCM) of civil engineering structures. In order to realize the optimal design and maintenance of asphalt pavement, a comprehensive reliability-based optimization methodology considering the life-cycle cost (LCC) is proposed in this paper. Considering the powerful ability of Artificial Neural Networks (ANNs) to solve complex and nonlinear problems, ANNs are implemented to predict the performance of asphalt pavement based on the training data (i.e. structural, traffic, climatic, and performance parameters) selected from the Long-Term Pavement Performance (LTPP) program. Monte Carlo simulation (MCS) with Importance Sampling (IS) is conducted based on the obtained ANNs model to calculate the life-cycle reliability of asphalt pavement. Finally, the expected LCC including the initial construction cost, the preventive maintenance cost, inspection cost, users cost, and salvage value is minimized while maintaining a prescribed life-cycle reliability level for asphalt pavement. Several applications are presented to investigate the effects of traffic and climatic parameters on reliability-based optimum cost solution. [ABSTRACT FROM AUTHOR]

Different types of responses have been considered in the past as the driving forces of the top-down cracking (TDC). The horizontal tensile strain at the surface is the most appropriate response of pavement structures for analysing TDC. In computing the horizontal strains, most of the mechanistic design methods of asphalt pavement consider that pavement layers are fully bonded and bottom-up cracking is the critical type of fatigue distress. The bonding condition between pavement layers is one of the significant factors influencing pavement performance. In this research, the effects of interface bonding conditions on top-down fatigue cracking are investigated based on the horizontal tensile strain at the surface. Analysis procedures are conducted using of Lucas algorithm and integration, summation and extrapolation (ISE) methods to determine the horizontal strain responses of asphalt concrete (AC) layer at the surface accurately. The results reveal that the AC layer thickness, type of base layer material and temperature affect the horizontal strains at the surface and debonded locations significantly. When the layers of thick pavement with cement-treated base (CTB) are fully bonded, the TDC is a dominant type of distress at different temperatures analysed, while for the thick pavement with granular base (GB) the surface-initiated cracking occurs only at high temperature. Due to the interface debonding in the thick pavement, the maximum horizontal strains vary at different locations and failure may appear simultaneously at the top and bottom of AC layers or only at one of those regions. For the thin pavement structure, the layer interface bonding conditions hardly influence the mechanistic response at the surface and the pavement with GB is more vulnerable to bottom-up cracking, whereas the likelihood of TDC increases at high temperature for the thin pavement with CTB. [ABSTRACT FROM AUTHOR]

Featured Application: Evaluation of bond strength between pavement layers. A poor bond between the layers constituting an asphalt pavement can cause structural problems such as slippage, delamination, and top-down cracking. These are consequences of the pavement being unable to act as a continuous element and to properly transmit the effects of the traffic to underlying layers. The aim of this research was to characterize an asphalt emulsion with low asphalt content using the Mexican standard and to evaluate its performance through the Laboratorio de Caminos de Barcelona (LCB) shear testing. Cationic slow setting (SS) and cationic rapid setting (RS) asphalt emulsions were tested by varying the asphalt contents, dosages, and cure times. The slow set emulsions presented a greater fracture energy than did the rapid set emulsions; a dose of 0.3 L/m2 provided the same level of resistance as a 0.5 L/m2 dose; and a 55% asphalt content provided greater resistance than the 60% asphalt content. [ABSTRACT FROM AUTHOR]

The durability, robustness, and long-term stability of optical-fiber-based sensors applied to practical engineering have always been challenging problems. Refer to the sensors embedded in asphalt pavements, the situation becomes serious and feasible sensors with enhanced function are in high demand. Therefore, an improved design to configure the quasi-distributed and distributed optical fiber sensors and FBG-based point sensors for monitoring the three-dimensional information of multilayered asphalt pavements is needed. The in-field data declare that the transversal, longitudinal, and vertical deformations of the tested urban asphalt pavement are mainly affected by temperature. The M-shape strain profile induced by heavy vehicles can decrease to the regular state in approximately 30 min after unloading. The tested asphalt pavement presents good structural performance to bear the tensile strain and permanent deformation. The high survival ratio and the good robustness of the proposed sensors against the harsh construction and operation environment validate the feasibility and reliability for the long-term monitoring. Improved design proposals on the construction scheme of asphalt pavement are also addressed to control the strain of the established asphalt concrete course in relatively low level. [ABSTRACT FROM AUTHOR]

The interface bonding condition between asphalt concrete layers is unquestioned as one of the significant factors influencing pavement performance. In order to research the interface characteristics of asphalt pavement under traffic loading, this paper presents a procedure to estimate shear strength between the asphalt layers via a direct shear test where both normal and shear stresses are applied to the interface. To do this, first, laboratory testing was conducted under varying conditions of temperature, vertical pressure, and tack coat application rate to analyze the influence of each parameter on interface shear strength. Second, the results from the tests were statistically analyzed for the significance level of each factor on interface shear strength. Finally, prediction models describing interface shear strength under the combined effect of shear and normal stresses at three different temperature levels are proposed and their feasibility is validated. All things considered, findings of this study hope to lead to a greater understanding of the monotonic behavior of interface performance in asphalt pavements. [ABSTRACT FROM AUTHOR]

During the past thirty years, interface bonding between pavement layers has been a topical subject worldwide to research. In this context, many researchers have developed and utilized their own devices to investigate the properties of pavement interfaces. In the absence of an international standard procedure for interface bonding, it is inevitable that testing results are not comparable in all cases. In addition, various conducted studies reveal that parameters such as temperature, loading conditions, materials and so on exert an influence on interface properties. This paper aims to deal with the matter effectively via a thorough and comprehensive review of interface bond testing to lay the groundwork for standardization procedure. For this purpose, first, a general overview of interface bond function and its impact on pavement performance is presented. Then, different types of interface bond test methods according to loading conditions are explained; furthermore, the configuration of various setups is discussed and their function is compared together. Finally, given the prior experiences, a framework for a methodical approach to a standard evaluation of pavement interfaces is presented. [ABSTRACT FROM PUBLISHER]

Experimental results from field and laboratory investigations using a ground-coupled ground penetrating radar (GPR), dielectric measurement, magnetic imaging tomography (MIT) and dynamic cone penetrometer (DCP) tests are presented. Dielectric properties of asphalt pavement and stabilised and unstabilised pavement foundation materials were evaluated in the laboratory in frozen and unfrozen conditions. Laboratory test results showed that dielectric properties of materials back-calculated from GPR in comparison to dielectric gauge measurements are strongly correlated and repeatable. For chemically stabilised materials, curing time affected the dielectric properties of the materials. Field tests were conducted on asphalt pavement test sections with different foundation materials (stabilised and unstabilised layers), drainage conditions and layer thicknesses. GPR and MIT results were used to determine asphalt layer thicknesses and were compared with measured core thicknesses, while GPR and DCP were used to assess foundation layer profiles. Asphalt thicknesses estimated from GPR showed an average error of about 11% using the dielectric gauge values as input. The average error reduced to about 4% when calibrated with cores thicknesses. MIT results showed thicknesses that are about 9% higher than estimated using GPR. Foundation layer thicknesses could not be measured using GPR due to variations in moisture conditions between the test sections, which is partly attributed to variations in gradation and drainage characteristics of the subbase layer. [ABSTRACT FROM AUTHOR]

The lateritic gravel routinely used in the midwest region of Brazil for pavement construction is no longer found near the urban centers. Thus, there is an increasing need for studies of alternative materials to replace it. This study presents an evaluation of the use of fine quarry wastes. An experimental test asphalt pavement was built with conventional materials and a soil-fine quarry waste mixture. Field tests were conducted to assess the behavior of these materials. It was verified that this waste is able to provide the same performance levels for low-volume roads while offering environmental and economic advantages. [ABSTRACT FROM AUTHOR]