Asphalt Concrete Overlays Research Articles

Machine learning-based technology for asphalt concrete pavement performance decision-making in hot and humid climates

Highway state agencies incur significant budget savings through optimal allocation of pavement Maintenance, Rehabilitation, and Reconstruction (MR&R) activities. These activities require robust prediction models that can handle large-scale, real-world data and can forecast pavement performance in the long run. Unfortunately, the traditional performance prediction models have been questionable in terms of efficiency and accuracy, are based on a limited number of explanatory variables, and are designated to predict short-term (up to five years) pavement conditions. Therefore, the goal of this study was to propose a machine learning-based technology that can predict the field performance by up to 11 years of Asphalt Concrete (AC) overlays placed on asphalt pavements in Southern states in the US based on key project conditions. The proposed technology resulted from assessing the prediction accuracy of machine learning algorithms, including Decision-Tree (DT), eXtreme Gradient Boosting (XGBoost), Artificial Neural Network (ANN), and ensemble-learning method, in forecasting the Pavement Condition Index (PCI) as the pavement performance indicator. For each algorithm, six models were developed sequentially based on historical pavement condition data collected from the Louisiana Department of Transportation and Development (LaDOTD) Pavement Management System (PMS) database. The six models learned from 892 log miles of randomly placed AC overlay sections in Louisiana. The output of these models was the future PCI of AC overlays at a biannual rate from one to 11 years. The findings showed that XGBoost and ensemble learning showed similar performance during model training and were further evaluated using the testing dataset. During model testing, the ensemble learning method yielded higher prediction accuracy than other algorithms, with R2 values decreasing from 0.77 at age 1 to 0.67 at age 11, Root Mean Square Error (RMSE) values increasing from ±1.65 to ±4.74, and Mean Absolute Error (MAE) increasing from 1.24 to 4.59. The resulting models can be used by state agencies to replace traditional prediction techniques.

Analysis of reflective cracking in asphalt overlaid jointed concrete airfield pavements using a 3D generalized finite element approach

ABSTRACT Asphalt Concrete (AC) overlays are a common strategy for maintaining PCC airfield pavements. However, the movement of joints in the underlying pavement may lead to reflective cracks propagating to the overlay. The problem is highly three-dimensional resulting in mixed mode of cracks due to the aircraft gear loading configurations and underlying concrete pavement joint spacing and design. The development of a 3D model of airfield pavements to predict reflective cracking using Finite Element Method (FEM) and Generalized Finite Element Method (GFEM), is presented in this study. GFEM enrichment strategy and global-local approach are used to achieve efficient framework for developing the models from both computational and user time perspective. Viscoelastic fracture analysis was performed using elastic-viscoelastic correspondence principle. Sensitivity of the domain size, order of approximation and boundary conditions are investigated in the numerical simulations. It is shown that the crack initiation and propagation is a combination of Mode-I (tensile) and Mode-II (shearing) crack opening. The presented models contributes to the mechanistic empirical reflective cracking design algorithm for the FAA pavement design program.

Development of a full-Scale approach to predict overlay reflective crack

ABSTRACT Resurfacing a moderately deteriorated Portland cement concrete (PCC) pavement with asphalt concrete (AC) layers is considered an efficient rehabilitation practice. However, reflective cracks may develop shortly after resurfacing because of discontinuities (e.g. joints and cracks) in existing PCC pavement. In this paper, a new accelerated full-scale testing approach was developed to study reflective crack growth in AC overlays. Two hydraulic actuators were used to simulate a moving dual-tire assembly with a loading rate of more than five-thousand-wheel passes per hour. A load cycle consists of three steps, simulating a tire approaching, moving across, and leaving a PCC discontinuity. Experiments were conducted to compare the reflective crack behaviour of two overlay configurations. Both test sections were fully cracked in less than an hour. The initiation and propagation of reflective cracks were explicitly documented using crack detectors in conjunction with a camera. The proposed full-scale testing protocol offers a repeatable and efficient approach to systematically investigate the effects of various overlay configurations, thus enabling the identification of optimal design against reflective cracking.

Mitigating Reflection Cracking in Asphalt Concrete Overlays with ECC and Geotextile

The rehabilitation of deteriorated pavements using Asphalt Concrete (AC) overlays consistently confronts the reflection cracking challenge, where inherent cracks and joints from an existing pavement layer are mirrored in the new overlay. To address this issue, the current study evaluates the effectiveness of Engineered Cementitious Composite (ECC) and geotextile fabric as mitigation strategies. ECC, characterized by its tensile ductility, fracture resistance, and high deformation capacity, was examined in interlayer thicknesses of 7, 12, and 17 mm. Additionally, the impact of geotextile fabric positioning at the base and at 1/3 depth of the AC specimen was explored. Utilizing the Overlay Testing Machine (OTM) for evaluations, the research demonstrated that ECC17 significantly mitigated reflection cracking, showing a notable 764% increase in the number of load cycles to failure (Nf) compared to the Geotextile Base (GB) specimen. Against the Reference Specimen (RS), ECC17 exhibited a remarkable 1307% enhancement in Nf values, underscoring its effectiveness. Geotextile fabric, particularly at 1/3 depth, demonstrated notable resistance but was overshadowed by the performance of ECC interlayers. The results clearly indicate that ECC, especially ECC17, stands out as an effective solution for mitigating reflection cracking, including joints, in AC overlays.

Case Study on Using Warm Mix Asphalt at Reduced Production Temperatures for Balanced Mix Design

This study provides a case study to illustrate the feasibility of using warm mix asphalt (WMA) at lower production temperatures to design asphalt mixtures with balanced rutting and cracking resistance in a laboratory setting. Two balanced mix design (BMD) modification approaches were evaluated to modify an existing Superpave mix design with unbalanced performance because of inadequate cracking resistance: (1) adding asphalt binder and (2) using WMA with a surfactant-based chemical additive. The modified mix designs were tested with the indirect tensile asphalt cracking test and high-temperature indirect tensile strength test to determine compliance with the Alabama Department of Transportation’s (ALDOT’s) BMD performance requirements. The original and modified mix designs were then tested in the modified overlay test to characterize their reflective cracking resistance, and the results were input into the Texas Asphalt Concrete Overlay Design System (TxACOL) software for theoretical asphalt overlay design simulations. Finally, asphalt binder testing was conducted to determine the impact of BMD modifications on the rheological properties of extracted binders. Laboratory testing showed that both BMD modifications improved the cracking resistance of the mix design but through different mechanisms. All the modified mix designs met ALDOT’s BMD requirements with balanced rutting and cracking resistance at their corresponding optimum binder content (OBC), which was 0.4%–0.7% higher than the volumetric OBC, respectively. TxACOL simulations showed that BMD modifications significantly improved the predicted reflective cracking performance and service life of asphalt overlays, but the improvement varied depending on the underlying pavement and traffic conditions.

RETRACTED: Improving the resistance of asphalt pavements against cracking with an interlayer: A comprehensive review

Asphalt concrete overlays are used for flexible or rigid road pavements when their function or structure deteriorates and exceeds an unacceptable extent. The life span of asphalt overlay decreases markedly if the old pavement that goes under rehabilitation is subjected to intense cracking. What causes this is the spread of the cracks in the old pavement onto the surface of the asphalt overlay; a phenomenon which is called reflective cracking. Despite the fact that reflective cracking is the most frequent mechanism of failure in rehabilitated pavements, its effect is usually overlooked in the design of overlays. A lack of understanding of the mechanical behavior of reinforced asphalt overlays is the primary reason behind this attitude, which can lead to imprecise design solutions. This paper first aims to review different aspects of mechanical interaction between geosynthetic material and asphalt overlay. Afterwards, essential considerations need to be considered in the design procedure to obtain an efficient reinforced-rehabilitated bituminous pavement structure are discussed.

Laboratory investigation into the crack propagation mechanism of geosynthetic reinforced asphalt concrete using digital image correlation technique

ABSTRACT Geosynthetic reinforcement has proven effective in mitigating reflective cracking in new pavement overlays. This study aimed to compare the ability of five different geosynthetic reinforcement products to alleviate cracking in overlays. Each product was sandwiched within a two-layered asphalt concrete (AC) beam specimen and subjected to a four-point notched beam fatigue test. The study monitored crack propagation, understood crack propagation mechanisms, and quantified crack lengths in different geosynthetic-reinforced AC beam specimens during a notched beam fatigue test using the digital image correlation (DIC) technique. The DIC analysis generated full-field displacement and strain contours, depicting the damage mechanisms of geosynthetic reinforcement products in AC overlays under fatigue loading. The quantitative analysis measured the cracked areas caused by each product. The interfacial damage observed in various geosynthetic-reinforced beam specimens under different test conditions suggested that the failure modes of AC beam specimens reinforced with different products varied, and choosing the right product for a project depended on the pavement conditions, geosynthetic product properties, and tack coat properties. Finally, the predictive algorithms presented in this paper allow for predicting the failure mode generated by different geosynthetic products for different overlay conditions in the field, providing valuable insight for pavement engineers.

Comparative Analysis of Reinforced Asphalt Concrete Overlays: Effects of Thickness and Temperature.

Reflection cracking in asphalt concrete (AC) overlays is a common form of pavement deterioration that occurs when underlying cracks and joints in the pavement structure propagate through an overlay due to thermal and traffic-induced movement, ultimately degrading the pavement's lifespan and performance. This study aims to determine how alterations in overlay thickness and temperature conditions, the incorporation of chopped fibers, and the use of geotextiles influence the overlay's capacity to postpone the occurrence of reflection cracking. To achieve the above objective, a total of 36 prism specimens were prepared and tested using an overlay testing machine (OTM). The variables considered in this study were the thickness of the overlay (40, 50, and 60 mm), temperature (20, 30, and 40 °C), mix type (reference mix and mix modified with 10% chopped fibers by weight of asphalt cement), and the inclusion of geotextile fabric at two positions (one-third of the depth from the base and at the bottom). The research outcomes revealed that a decreased temperature and thicker overlay led to a higher resistance to crack initiation and full propagation, as indicated by the values of critical fracture energy (Gc) and crack progression rate (CPR). Furthermore, the study observed the enhanced crack resistance of overlays in the presence of geotextiles, whether at the bottom or one-third of the depth from the bottom, with superior performance of the former. Despite a slight enhancement in certain properties, the incorporation of chopped fibers in the overlays did not substantially improve the overall performance compared to the reference specimens. Overall, the study provides valuable insights into the variables that influence the ability of AC overlays to mitigate reflection cracking. These findings will aid engineers and designers in making informed decisions regarding overlay design and construction.

Study on Thermal Reflective Cracking of Asphalt Concrete Overlays on Concrete Pavements Under Moderate Temperature Variations Using Finite Element Model

This study investigated the effects of moderate daily temperature variations on reflective cracking in asphalt concrete (AC) overlays on Portland cement concrete (PCC) pavements using three-dimensional (3D) finite element (FE) modeling. The FE model consists of an AC overlay on top of PCC slabs, followed by aggregate base and subgrade. The year-round temperature variations were divided into discrete groups using a clustering technique and each group was applied separately in the FE model. The maximum stress and strain values associated with each temperature variation group were determined using the FE model and used as the driving force corresponding to the thermally induced damage in the AC overlay. The results show that the maximum stress and strain values in the overlay depend on the hourly temperature variation as well as the seasonal temperature profile. The daily temperature variation controls the deformation of the underlying PCC slabs, whereas the seasonal temperature profile determines the viscoelastic properties of the AC overlay. The estimated maximum tensile stress and strain values suggest that the AC overlay is primarily subjected to damage from repetitive thermal loading instead of one-time fracture events for moderate temperature variations. In addition, when the AC overlay is fully bonded to the PCC slabs, the thermal strains are much greater than the traffic induced strains, indicating a high possibility of thermal reflective cracking being the dominant damage mechanism for these cases.

Machine-Learning-Based Framework for Prediction of the Long-Term Field Performance of Asphalt Concrete Overlays in a Hot and Humid Climate

Pavement performance prediction models are used by state agencies to determine pavement maintenance and rehabilitation strategies. However, most performance prediction models are based on a limited number of parameters and a maximum prediction period of five years. With the ever-increasing amount of available pavement performance data, machine-learning techniques have become a promising alternative to traditional performance prediction models. The objective of this study was to develop a machine-learning-based framework for states with a hot and humid climate that can predict the long-term field performance (up to 11 years) of asphalt concrete (AC) overlays on asphalt pavements based on key project conditions. The pavement condition index (PCI) was used as the pavement performance indicator. Two machine-learning algorithms, namely, random forest (RF) and CatBoost, were examined. A total of 892 log-miles of AC overlay data were obtained from the Louisiana Department of Transportation and Development Pavement Management System database. Based on the collected data, six models were trained (for each algorithm) and validated to predict the PCI of AC overlays for up to 11 years. The results indicated that the RF algorithm yielded higher accuracy than the CatBoost algorithm. Therefore, the RF-based models were considered in the proposed decision-making framework.

Mitigation of Reflection Cracking in Asphalt Concrete Overlay on Rigid Pavements

Reflective cracking is one of the primary forms of deterioration in pavements. It is widespread when Asphalt concrete (AC) overlays are built over a rigid pavement with discontinuities on its surface. Thus, this research work aims to reduce reflection cracks in asphalt concrete overlay on the rigid pavement. Asphalt Concrete (AC) slab specimens were prepared in three thicknesses (4, 5, and 6 cm). All these specimens were by testing machine designed and manufactured at the Engineering Consulting Office of the University of Baghdad to examine for the number of cycles and loads needed to propagate the reflection cracking in the asphalt concert mixture at three temperatures (20, 30, and 30°C). It was noticed that the higher thickness AC mixtures increased the reflection cracking performance life of the AC overlay. Also, it was found that the number of crack initiation and failure cycles increased as the temperature increased. In contrast, the increased temperature decreased the required load to crack initiation and failure load in the sample.

Field Performance and Cost-Effectiveness of Chip Seals and Asphalt Concrete Overlays with and without Asphalt Concrete Stripping Damage

The objective of this study was to evaluate the effects of asphalt concrete (AC) stripping damage on the field performance and cost-effectiveness (CE) of chip seals and AC overlays in pavement maintenance and rehabilitation. To achieve this objective, in-service pavement sections were selected from the Louisiana pavement management system (LaPMS) database and the presence of moisture damage was confirmed through the visual inspection of extracted cores. Sections were categorized according to traffic volume and their pavement condition index before treatment (PCI-). Road sections in each group were then divided into two groups as stripped and non-stripped sections. The average deterioration rate (ADR), extension in pavement service life (ΔPSL), average condition improvement over the treatment service life (PI), and CE were compared for stripped and non-stripped sections. Results showed that for chip seal sections, moisture damage negatively affected the performance of the sections with PCI- < 80 and low traffic volumes. For sections with PCI- > 80, similar performance was observed for stripped and non-stripped sections. For AC overlays, moisture-induced damage significantly affected the long-term pavement performance at all traffic levels. On average, moisture-induced damage decreased ΔPSL, PI, and CE of AC overlays by 5 years, 24%, and 0.5%, respectively. Overall, results of the study demonstrated that moisture damage has a significant effect on the performance of chip seal and AC overlay. Therefore, it is critical to identify and repair stripped sections before the maintenance and rehabilitation of in-service pavements to ensure adequate performance and optimum CE.

Investigating the Influence of Joint Reinforcements of Portland Cement Concrete Slabs Under Asphalt Concrete Overlays on Vertical Deflections Using Accelerated Pavement Testing

Joint gaps between slabs in underlying Portland cement concrete (PCC) pavements are critical factors in the life span of asphalt concrete (AC) overlays. Therefore, being informed about the vertical deflections that may occur around the joints is important. In this study the joints were reinforced with three different materials: ethylene propylene diene monomer (i.e., rubber joint filler [RJF] reinforcement), bitumen-based sealant (i.e., rubber plate [RP] reinforcement), and steel plate (SP) (i.e., SP reinforcement), to limit the vertical movement of the underlying PCC. Tests were conducted at the accelerated pavement testing facility for two different AC overlay thicknesses, 50 mm and 100 mm, during 100,000 passages to investigate the influence of AC overlay thickness variations on slab vertical deflections and to also evaluate types of joint reinforcement on slab vertical deflections. For 50-mm thick AC overlay, the most effective joint reinforcements to prevent deformations caused by loading were RP, RJF, and SP; for a 100-mm thickness, this was determined to be RJF, SP, and RP, respectively.

Implementation of Finite Element and Fracture Mechanics Based Reflection Cracking Models for Asphalt Concrete Overlay of Existing Asphalt Concrete Pavement in AASHTOWare Pavement ME Design

The reflection of existing cracks from the underlying pavement is one of the primary modes of failure for rehabilitated asphalt concrete (AC) pavements with AC overlays. The AC overlay design philosophy is to delay the onset of reflection cracking or to eliminate it entirely. In recent years, rehabilitation designs are being optimized not just for cost effectiveness, but also to produce more reliable, sustainable, and environmentally friendly designs that require more detailed and sophisticated methodologies. The new finite element and fracture mechanics based reflection cracking models were developed under National Cooperative Highway Research Program (NCHRP) Project 1-41 to improve design methodology. The new models were generally compatible with the AASHTOWare Pavement ME Design (AASHTOWare) framework. The difference included the computation of critical pavement responses (i.e., stress intensity factors) and others, and thus modified. The modified models were calibrated and validated using Long-Term Pavement Performance projects. The calibration of reflection cracking models produced satisfactory goodness of fit with no significant bias. Thus, the modified reflection cracking models were successfully adapted and deployed in the AASHTOWare software to create a new improved AC overlay of existing AC pavement design methodology. This new methodology represents a paradigm shift from the traditional pavement design procedures. It significantly increases the capability of the pavement design software to simulate all the loadings experienced by AC overlay, estimate pavement responses, and predict reflection cracking based on pavement responses. This paper discusses the implementation of NCHRP 1-41 reflection cracking models for AC overlay of existing AC pavements into AASHTOWare software.

Characterization of Shear Resistance of Interlayer between Concrete Bridge Deck and Asphalt Concrete Overlay Utilizing Inclination Shear Test

AbstractHot-mix asphalt (HMA), which can be employed as a wearing course on concrete bridge decks, provides a smooth surface for riding. However, some bridge deck asphalt surfaces experienced layer...

Field Performance Evaluation of High Polymer-Modified Asphalt Concrete Overlays

The objective of this paper was to assess the viability of using high polymer (HP) modified asphalt concrete (AC) mixtures in Virginia as a reflective crack mitigation technique or when deemed appropriate as a tool for increased crack resistance on higher volume facilities. This was achieved by compiling and evaluating routine distress survey data against pre-paving distress survey data for relevant in-service HP pavements constructed between 2015 and 2018 and comparing them with several control in-service conventional polymer-modified asphalt (PMA) pavements. This is the first effort in North America to provide a detailed field performance of HP AC mixtures. In general, none of the evaluated mixtures (HP or PMA) was able to prevent reflective cracking completely. The HP sections showed the most promising performance 5 years after construction regardless of traffic level and the pre-existing pavement conditions. The pavement management system data for the reviewed sections indicated a potential controlling effect of the joint condition of the underlying jointed concrete pavement layer regardless of the asphalt mixture type employed (PMA or HP). Moreover, performance evaluations using the network-level pavement management data were conducted to estimate the life expectancy of HP AC overlays. Two different approaches and three levels of analysis were undertaken. Overall, PMA and HP AC overlays had an average predicted service life of 6.2 and 8.3 years, respectively, indicating a 34% extension of performance life of the AC overlays with high polymer modification.

Multi-Level Laboratory Performance Evaluation of Conventional and High Polymer-Modified Asphalt Mixtures

Asphalt concrete (AC) overlays have been one of the most common treatments used by the Virginia Department of Transportation (VDOT) for maintaining/rehabilitating pavements. However, when the overlay is placed on existing composite pavements or cracked AC pavements, differential movements across any cracks or joints can result in physical tearing of the AC overlay. Thus, the long-term performance of many AC overlays will highly depend on their ability to resist cracking. The purpose of this study was to assess the viability of using high polymer-modified (HP) AC mixtures in Virginia as a crack mitigation technique or when deemed appropriate as a tool for increased resistance to rutting and cracking on higher volume facilities. Another objective was to assess the ability of various testing protocols to discern the performance of pavements through a comprehensive evaluation of three conventional polymer-modified (PMA) and five HP field-produced mixtures placed in Virginia. This included laboratory testing at multiple levels of complexity (basic, intermediate, and advanced) on collected asphalt binders, plant-produced asphalt mixtures, and field cores. The performance characteristics of PMA and HP mixes were evaluated in the laboratory in relation to durability and resistance to rutting and cracking. Based on the mixes tested, stone matrix asphalt (SMA) mixes showed better performance than dense-graded surface mixes (SM) regardless of the asphalt binder type. Moreover, HP mixes showed better performance than PMA mixes regardless of the mixture type. Overall, SMA-HP mixes showed the most promising performance among all evaluated mixes.

Performance of AC overlays using geogrids on PCC contraction joints

It is widely known that vertical displacements and strains occur on the joints and these cause defects on the asphalt concrete (AC) overlays on existing Portland cement concrete (PCC) pavements. Various approaches were introduced to minimize these defects. In this study, the effect of joint support formed using the geogrid material with grout mortar on the vertical displacement of PCC and the strain at the bottom of the AC layer. Produced layers were exposed to 1,186,000 Equivalent Single Axle Load (ESAL) in an APT (Accelerated Pavement Test) facility and the results were monitored. According to the obtained results, the use of AC overlay reduces vertical displacement in the PCC by 75%. When geogrid reinforced AC overlay was used, an additional reduction in displacement by 41.2% was achieved. Geogrid reinforcement reduced strain values formed at the bottom of the AC layer from 29.5% to 92.5%. The use of geogrid at joints instead of increasing the thickness of the AC layer from 50 to 80 mm resulted a more significant reduction in both strain and displacement. Besides, the usage of a geogrid interlayer instead of increasing the thickness of the AC layer also provided a significant cost reduction of 57.9% in overall cost.

State of the Practice for High Polymer-Modified Asphalt Binders and Mixtures

The objective of this paper was to provide information on the state of the practice for using high polymer-modified (HP) asphalt concrete (AC) mixtures in the United States (U.S.) and Canada. This information was collected through a survey of U.S. and Canadian provincial agencies combined with a search of HP-related specifications, special provisions, and field trials or pilot projects previously constructed. Moreover, the Virginia Department of Transportation’s (VDOT) current state of the practice with regard to using HP paving material was determined. This was achieved through a navigation of VDOT databases to report tonnage and types of produced HP AC mixtures, and experience, lessons learned, and best practices on behalf of multiple asphalt contractors in the area. The majority of the agencies that currently use or have constructed field trials and pilot projects using HP AC mixtures are located in the eastern part of the U.S. In general, HP AC mixtures have been used in a wide range of applications ranging from full-depth AC to thin AC overlays under heavy traffic on interstates and slow-braking loads at intersections. No major field-related construction issues in relation to mixing temperatures and in-place compaction of HP AC mixtures were reported, and standard construction practices and equipment were used. Finally, good communication between the polymer/binder supplier and the contractor, and solid planning before conducting the work were important lessons learned with regard to paving with HP AC mixtures.

Impact of high polymer modification on reflective cracking performance life of asphalt concrete overlays

Reflective cracking is one of the major type of distresses associated with the use of asphalt concrete (AC) overlays for rehabilitating deteriorated asphalt pavements. The differential movements across the underlying cracks due to the combined effects of heavy wheel loads and temperature fluctuations result in physical tearing of the AC overlay. Thus, the long-term performance of AC overlays highly depends on their ability to resist reflective cracking. While conventional polymer-modified (PMA) AC mixtures with 2–3% polymer content have shown improved long-term performance when used as overlays, it is also believed that AC mixtures with higher polymer content may offer additional advantages for flexible rehabilitated pavements subjected to heavy and/or slow-moving traffic loads. This paper describes the research effort completed to evaluate the reflective cracking performance life of high polymer-modified (HP) AC mixtures used as overlays. Sixteen AC mixtures were produced in the laboratory using PMA and HP asphalt binders. These mixtures were evaluated in terms of their dynamic modulus and resistance to reflective cracking. The engineering properties and laboratory performance data were combined into a mechanistic analysis that took into consideration the existing AC pavement condition, mixture-specific material properties, traffic condition, and climate. Overall, the HP AC mixtures resulted in an increase in both time to reach initial cracking and reflective cracking performance life of the AC overlay when compared to their respective PMA AC overlay mixtures.