Asphalt Overlays Research Articles

Shearing Properties of Epoxy and Epoxy Bitumen as Bonding Material of Asphalt Overlay on Ultra-High Performance Concrete Slab

Shearing Properties of Epoxy and Epoxy Bitumen as Bonding Material of Asphalt Overlay on Ultra-High Performance Concrete Slab

Evaluation for long-term skid resistance of ultra-thin asphalt overlay based on texture characteristics

To evaluate the durability of ultra-thin asphalt overlays in terms of skid resistance accurately, the long-term degradation trends in texture characteristics need to be carried out comprehensively. In this paper, three types of ultra-thin asphalt overlays with different gradations were selected. The long-term abrasion test was conducted, with friction coefficient and texture characteristics tested in each abrasion cycle. Additionally, the stress state changes at the interface of the tire and mixtures were also obtained. Finally, the reliability of texture characteristics was validated based on the correlation between different indicators. The results show that the friction coefficient and texture characteristic show a two-stage decay pattern during the abrasion process, with a significant decrease in stress between 0.75 and 2.5 MPa at the interface of tire and mixtures. The surface mean texture depth (SMTD), root-mean-square deviation of surface (Sq), peak density of surface (Spd), and spatial fluctuations of texture (Δα) were correlated with British pendulum number (BPN) strongly, and the Sq and Δα were recommended as reliable evaluation parameters for the long-term skid resistance of ultra-thin asphalt overlays. This study provides theoretical guidance for the optimal design and field monitoring of ultra-thin asphalt overlays from the perspective of surface texture characteristics.

From data to decision: integrated approach to pavement preservation in Iowa through treatment effectiveness analysis

ABSTRACT This investigation seeks to enhance ‘Iowa's Pavement Preservation Guide’ with a data-informed decision-making framework. Iowa DOT's databases were used as the data source for evaluating pavement performances under different preservation treatment regimens and determining the effectiveness of those strategies. Five preservation treatment methods for flexible and composite pavements, namely, crack sealing-and-filling, microsurfacing, slurry sealing, patching, and thin hot mix asphalt (HMA) overlays were evaluated using historic data from about 7000 road segments between 1998 and 2020. The data included various attributes describing pavement, road, and traffic characteristics required for analysing condition-based performance and treatment impacts. Two key indicators, service life extension (LE) and index benefit (IB), were defined and used to quantify treatment effectiveness in terms of pavement condition improvement and impact on deterioration rate. The treatment-effectiveness indicators were then factored into the cost analyses to assess the cost-effectiveness of preservation strategies. The results of the treatment effectiveness analysis were used to develop decision matrices that provide insights for selecting preservation treatments based on benefit–cost analysis considering both the overall condition and the dominant distress. This approach to treatment effectiveness highlighted the distinction between an optimum pavement preservation strategy and one that targets maximum service life extension.

Modelling Asphalt Overlay As-Built Roughness Based on Profile Transformation-Case for Paver Using Automatic Levelling System.

The as-built roughness, or smoothness obtained during pavement construction, plays an important role in road engineering since it serves as an indicator for both the level of service provided to users and the overall standard of construction quality. Being able to predict as-built roughness is therefore important for supporting pavement design and management decision making. An as-built IRI prediction model for asphalt overlays based on profile transformation was proposed in a previous study. The model, used as basis for this work, was developed for the case of wheeled pavers without automatic screed levelling. This study presents further development of the base prediction model, including the use of an automatic screed control system through a long-distance averaging mobile reference. Formulation of linear systems that constitute the model are presented for the case of a wheeled paver using contactless acoustic sensors set-up over a floating levelling beam attached to the paver. To calibrate the model, longitudinal profile data from the Long-Term Pavement Performance SPS-5 experiment was used, obtaining a mean error of 0.17 m/km for the predicted IRI. The results obtained demonstrate the potential of the proposed approach as a modelling alternative.

Field Performance and Cost-Effectiveness of Ultrathin Asphalt Overlay in Hot and Humid Climates

Field Performance and Cost-Effectiveness of Ultrathin Asphalt Overlay in Hot and Humid Climates

Research on the propagation mechanisms and meso-mechanical responses of reflective cracking on the asphalt overlays on concrete airfield pavement by Fiber Bragg Grating sensing technology

This study evaluated the propagation mechanisms and dynamic meso-mechanical responses of reflective cracking on the asphalt overlays on concrete airfield pavement based on flexible Fiber Bragg Grating (FBG) sensors. The encapsulated FBG sensors were efficiently calibrated, possessing outstanding capability for the measurement of transverse expansion of lateral reflective cracking propagation. Virtual three-point bending test model was proposed and validated by macroscopic indoor experiments. The DEM model facilitated quantifying the proliferation of reflective cracks, unraveling the trajectory from micro-crack inception to visible macroscopic manifestation. Results indicated that the emergence and elongation of the composite structure experienced three phases: the initiation and accumulation of microcracks, the extension of reflective cracking, and the ultimate penetration. The DEM simulation and FBG sensors were recommended to establish a mutually reinforcing mechanism for nuanced validation of reflective crack formation on the composite structures of asphalt overlays on concrete airfield pavement.

Fatigue performance of geosynthetic-reinforced asphalt using DIC

The main objective of this study is to evaluate the influence of geosynthetic reinforcement on the fatigue performance of asphalt overlays using double-layered specimens extracted from experimental sections. Notched beam fatigue tests were conducted, together with Digital Image Correlation (DIC) technique to assess the initiation and propagation of cracks, along with strains mobilized at the geosynthetic interface. The geosynthetic-reinforced specimen demonstrated notable improvement compared to the unreinforced counterpart in reducing vertical deformations with an increase in fatigue life by a factor of 7. DIC analysis demonstrated that geosynthetic reinforcement absorbed the tensile stresses from the crack tip and reduced the tensile strains, contributing to minimize the propagation of reflective cracks into the asphalt overlay. Overall, research findings contribute to understanding the factors that enhance fatigue life through the incorporation of geosynthetic reinforcements in asphalt 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.

Case Study: Validation of the Spectral-Analysis-of-Surface-Waves Method for Concrete Pavement Condition Evaluation

Before conducting pavement rehabilitation, the concrete pavement performance evaluation is more than necessary to assess the strength and analyze the internal condition. To evaluate the modulus performance of concrete pavement and provide theoretical support for subsequent maintenance and rehabilitation, the SASW (Spectral-Analysis-of-Surface-Waves) method, a non-destructive testing method based on surface waves, was used to determine the modulus of three in-service concrete pavements. At the same time, FWD (Falling Weight Deflectometer) testing and on-site coring were carried out at the measuring points. Through the analysis of modulus results measured in the field, it was found that the SASW method can accurately obtain the elastic modulus of the concrete layer and base layer. Compared with the concrete modulus measured by FWD, the modulus measured by the SASW method was closer to the uniaxial compressive modulus. Moreover, since the SASW method has the ability to provide gradient modulus varying with depth and determine the pavement thicknesses, it is reasonable to recognize the location of the inherent distress based on the region where the modulus suddenly decreases within one layer. The comprehensive evaluation of concrete pavement condition, including the modulus value and internal distress recognition, has the capability to assist in determining the design of overlay asphalt thickness and material.

Installation of geosynthetic interlayers during overlay construction: Case study of Texas State Highway 21

Geosynthetic interlayers in the form of geotextiles, geogrids, and geocomposites have been used to minimize reflective cracks and enhance overlay performance through functions such as stress relief, reinforcement and moisture barrier. However, proper geosynthetic installation and asphalt overlay construction practices are essential to the adequate performance of geosynthetic-reinforced asphalt overlays. In this study, various factors determining the successful construction of a geosynthetic-reinforced asphalt overlay are discussed in light of experiences during the construction of experimental test sections constructed in Texas State Highway 21. The project included nine different types of geosynthetic interlayers including four polymeric geogrid composites, three fiberglass geogrid composites, one fiberglass grid, and a fiberglass paving mat. The experimental test section included both sensor- and non-instrumented sections. The constructability evaluation of such experimental sections revealed that the primary factors influencing tack coat type and application rates include the pre-existing surface condition, geosynthetic type and their asphalt retention capacities. The geosynthetic installation procedures adopted in the experimental sections were proficient and comprised a specialized installation equipment that is capable of pre-tensioning the geosynthetics during the installation to minimize wrinkles and irregularities. Additionally, particularly high temperature of the pre-existing asphalt surface resulted in blistering of geotextile backing and subsequently leading into an excessive bleeding of tack coat through the geosynthetic apertures that resulted in tracking of construction equipment wheels. Recommendations on efficient geosynthetic installation and overlay construction techniques include adopting the tack coat type and application rates based on project-specific conditions, and using such tack coat to determine the asphalt retention capacity of the geosynthetic interlayer to be used in the project. Additional recommendations include minimizing the movement of construction vehicles on top of the geosynthetic interlayer, and adopting asphalt sanding technique to restore the friction between the paver and surface to minimize possible damage to the geosynthetic interlayer.

Machine learning based pavement performance prediction for data-driven decision of asphalt pavement overlay

This study is to develop pavement performance models using support vector regression and ensemble machine learning methods for selection of pavement overlay strategy. Predictive models of pavement distresses were developed based on the Long-Term Pavement Performance (LTPP) data and compared using support vector machine, random forest regression, gradient boosting machine, and stacking ensemble. Gradient boosting machine was found to be a more effective method to establish predictive models of rut depth and International Roughness Index. Stacking ensemble and random forest regression would provide reliable prediction of alligator cracking. The models developed based on the clusters of climate and traffic parameters were found to be more effective. Based on the developed performance models, the effects of asphalt overlays on pavement distresses and service lives were investigated. When the overlay with recycled asphalt concrete (AC) was applied, the propagation of alligator cracking was faster compared to the overlay with virgin asphalt mixture. Milling before overlay tended to slow the increase of IRI but fasten the development of rut depth.

Long-Term Performance and Forensic Evaluation of an Asphalt Pavement with Cold Central Plant Recycled Asphalt

In 2012 Virginia Department of Transportation constructed two test sections at the National Center for Asphalt Technology Test Track containing asphalt processed via cold central plant recycling (CCPR) with identical asphalt overlays. One section contained a stabilized base beneath the CCPR layer (Section S12), similar to a full-depth reclamation layer; the other included an unstabilized aggregate base beneath the CCPR layer (Section N4). Both sections were subjected to trafficking by loaded trucks for a total of 30 million equivalent single axle loads. Minor cracking was observed at the surface of the section with the unstabilized base; the section with the stabilized foundation exhibited no surface cracking. Furthermore, strain, pressure, and deflection measurements showed better performance for the section with the stabilized foundation than the section with the unstabilized base. Because of the relatively unchanged performance of Section S12, it was taken out of service to conduct a forensic investigation. This paper presents the analysis of the instrumentation results, coring, trenching, and mechanistic testing and modeling, to better understand and compare the performance between sections. The stabilized base was found to greatly reduce bending action in the section, exhibited no substantial rutting, but also contained what appeared to be some shrinkage cracks. However, these cracks did not propagate to the surface, indicating that the CCPR layer may be an effective crack mitigator. Further, it was found that mechanistic modeling using AASHTOWare Pavement ME design software overestimated the rutting but predicted similar international roughness index and cracking to that observed in the field.

Evaluation of Three Federal Highway Administration Targeted Overlay Pavement Solutions for Asphalt Pavements Based on Their Performances and Potential to Increase Pavement Service Life

The Federal Highway Administration Targeted Overlay Pavement Solutions (TOPS) program presents innovative overlay solutions for both asphalt and concrete pavements. The objective of this study was to conduct a comparative evaluation of three TOPS types for asphalt pavements, namely, Asphalt Rubber Gap-Graded, Stone Matrix Asphalt and High-Performance Thin Overlay as regards performance, how they extend pavement service life, and whether they can be used interchangeably. Asphalt binders from two sources were used in each of these three TOPS types, thus, providing a total of six TOPS mixtures. All TOPS passed the mixture performance tests where the test had a State Transportation Agency (STA) specified or a preliminary criterion, and the test results indicated that all three TOPS types can be used interchangeably. More specifically, all six TOPS mixtures met the Massachusetts Department of Transportation’s TOPS pilot specification criteria for rutting, moisture damage, and intermediate-temperature cracking. They also passed the mixture performance tests for reflective cracking and raveling based on criteria established by other STAs. AASHTOWare® Pavement Mechanistic-Empirical Design predictive models for bottom-up fatigue cracking indicated that 2 in. of a TOPS mixture placed on an existing in-service pavement can extend pavement service life between 11.2 and 14 years depending on the type of TOPS and source of binder. The maximum difference in service life between the six TOPS was slightly less than 3 years, although most of them were within 2 years of each other. Furthermore, none of the three TOPS types could be chosen to be the best TOPS.

Development of an indoor test method for evaluating the anti-reflection crack performance of asphalt overlay

Fatigue tests conducted in an indoor environment for evaluating the anti-reflection crack performance of asphalt overlay are associated with large specimen size and significant dispersion in the test results. To overcome these drawbacks, a test method based on small composite specimens and composite-specimen interface-cracking (CSIC) samples was developed to evaluate the anti-reflection crack performance of asphalt overlays. The effect of glass fiber gratings with three different sizes and no glass fiber grating on the anti-reflection crack performance of the asphalt overlays was compared and analyzed through fatigue tests. The results showed an evident anti-reflection crack effect in the specimens with glass fiber grating; the fatigue test with the CSIC specimens could effectively improve the precision of the test method and reduce the dispersion in the test results. Based on a fatigue test conducted through the ABAQUS finite element analysis software simulation, the feasibility of the evaluation method could be effectively verified. Our study can serve as a basis for the reasonable selection of reinforcing materials to extend the service life of asphalt overlays.

A simplified analysis method for long-span suspension bridges within the deck overlay retrofitting process from asphalt to UHPC

The steel-ultrahigh performance concrete (UHPC) lightweight composite deck (LWCD) is increasingly adopted by in-service steel bridges to address the fatigue cracking issue for orthotropic steel decks (OSDs) and the premature damage issue for asphalt overlays. While for in-service long-span suspension bridges that need to be retrofitted by LWCDs, the response of the UHPC layer in casting is complex. Within the UHPC casting process, the moment of the stiffening girder changes continuously as the self-weight of the stiffening girder changes in casting, and the change of moment will produce strains in the UHPC portion set earlier; in other words, the UHPC portion cast latter will produce strains in the UHPC portion cast earlier. If the resultant tensile strains are too high, the UHPC layer may crack within the casting process, which should be avoided. In this paper, a simplified analysis method, based on the linearized deflection theory, was proposed to rapidly obtain the response of long-span suspension bridges in retrofitting without significantly compromising the accuracy of the analysis results. A new solving method based on exponential functions was proposed, which is simpler than the commonly used hyperbolic function-based method. The proposed method was implemented as computer codes in Matlab and verified through two examples: a single-span suspension bridge and a three-span suspension bridge. The simplified analysis method was used to perform a detailed analysis for the Yichang Yangtze River Expressway Bridge (YYREB), a 960-m-long single-span suspension bridge in China, for which the existing asphalt overlay was replaced by an LWCD in 2021. In the analysis, three cast sequences were considered for the UHPC layer, i.e., from end to end, from mid-span to ends, and from ends to mid-span. It is revealed that the mid span-to-ends cast sequence produces the minimum tensile strain in UHPC, so the cracking risk of UHPC could be well controlled by using this casting method. Thus, the mid span-to-ends cast sequence was adopted by the YYREB within the deck overlay retrofitting process from asphalt to UHPC.

Bitumen stabilized materials as pavement overlay: Laboratory and field study

Bitumen stabilized materials applied as base courses have been used in many countries. In the southern Brazilian State of Rio Grande do Sul, two test sections were built using such mixes (in 2011 and 2015) as overlay asphalt emulsion base courses and have been under monitoring since then. In 2019, a new test section was built to evaluate mixes of granular materials and reclaimed asphalt pavement stabilized with emulsion and Portland cement as overlay base courses. The main objective of the research reported here was to evaluate the mechanical behavior of such materials and to assess their performance in the field during the years after construction. Indirect tensile strength, monotonic triaxial, and repeated load triaxial tests were carried out to obtain the necessary mechanical parameters. The data collected during the monitoring of the test sections were used to analyze the field performance in terms of permanent deformation. Besides, in situ moduli were obtained using backanalysis of deflection basins. The number of equivalent single axle loads (ESALs) for the analysis period was computed using data collected in toll plazas near the test sections. Using field and laboratory results and the South African TG2 performance model, it was possible to estimate the life of the studied pavements regarding permanent deformation. The TG2 model seems to underestimate the life of pavements with thick (>40 mm) asphalt layers. A model relating rutting to the number of ESALs was obtained, allowing the prediction of rutting of asphalt pavements overlaid by a bitumen stabilized base layer and asphalt wearing courses. Considering the test sections’ performances, the mixes proved to be efficient to improve structural capacity, also reducing the influence of the water level variation on pavement performance.

Performance Comparison of Break and Seat and Rubblization Rehabilitation Techniques for Reflection-Crack Mitigation: Case Study in Louisiana

Hot mix asphalt (HMA) overlays are constructed on Portland cement concrete (PCC) pavements to improve long-term performance. A significant disadvantage of using HMA overlays on PCC pavements is the development of reflection cracks. Reflection cracks are influenced by traffic loads and periodic temperature changes. The objective of the study was to compare field performance of two slab-fracturing (i.e., break and seat, and rubblization) techniques commonly used in Louisiana, U.S. Four PCC pavement rehabilitation projects with at least one slab-fracturing technique and a corresponding control section were evaluated. Field structural capacity and performance data were collected and analyzed to determine the effect of each reflection-crack mitigation technique on performance. Resilient modulus (Mr) of the existing subgrade was found to significantly influence the structural and functional performance of the pavement sections evaluated. Pavement sections with weaker subgrades were shown to be not suitable for slab-fracturing rehabilitation techniques. For the four field projects evaluated, rubblized test sections showed higher cracking resistance than the control sections. The break and seat technique did not consistently improve or reduce the crack resistance of pavement sections compared with their corresponding control sections because of variations in subgrade Mr values. Sections with smaller sized (i.e., 6 in. break pattern and rubblized particles) fractured particles exhibited higher cracking resistance. Rubblized and selected break and seat sections for the field projects evaluated exhibited lower overall performance compared with their corresponding control sections, which is attributed to other underlying subsurface conditions. Additional study is required to continuously monitor the pavement sections.

Survival Analysis of Concrete Overlays on Low-Volume Roads in Iowa

Concrete overlays are an important component of Iowa’s rural road network. More than 2,000 centerline miles of concrete overlays have been paved in Iowa over the last few decades, including many overlays on low-volume roads serving 400 vehicles per day or less. In this study, a survival analysis was performed using automated pavement condition data collected on Iowa’s concrete overlays to obtain a probabilistic assessment of concrete overlay service life, paying particular attention to the performance of overlays on low-volume roads. Concrete overlays were found to perform very well, with a 30-year survival probability of 85.3% for all projects to rehabilitation or reconstruction, and 76.6% for overlays only on low-volume roads. Survival life was reduced when the survival condition was changed to performance thresholds based on a pavement condition index (PCI) of 60/100 and an International Roughness Index (IRI) value of 170 in./mi, but was still good overall. Overlays tended to reach the failure condition for PCI before IRI, indicating that cracking is a more common distress than surface roughness. Another important finding was that concrete on asphalt overlays had a longer median survival life and a greater 30-year survival probability than concrete on concrete-unbonded overlays. Overall, concrete overlays have performed well in Iowa and are well suited to low-volume roads and rural county highways.

The Influence of Polypropylene Fiber and Silica Fume on the Mechanical Properties of No-Fine Concrete with Recycled Aggregate

No-Fines Concrete is a type of concrete produced without fine aggregate or sand. Because of its high porosity, it allows rainwater to seep into the ground, directly replenishing the groundwater aquifer. With a design load of three tons, no-fine concrete can be utilized as pavement for rural roads. Additionally, this type of concrete can be utilized as a sub-base material in both flexible and rigid pavements. Aside from No-Fines Concrete's permeability properties, asphalt overlays are another option. This research studied the impact of silica fume and polypropylene fiber on the properties of no-fine concrete with recycled aggregate. The ratios of cement to aggregate and water to cement were 1:4 and 0.3, respectively. The recycled aggregate was demolished reactive powder concrete used in percentages of 10, 20, and 30% as a substitution for coarse aggregate by volume. The recycled aggregate percentage of 10% was the optimal percentage as it showed the least adverse effect on the no-fine concrete mixes. The polypropylene fiber was then added to the no-fine concrete mixes with 10% recycled aggregate in the percentages of 0.5, 1, and 1.5% by volume. The optimum percentage of polypropylene fiber was 0.5%, which improved the mechanical properties of no-fine concrete. Silica fume was used as a partial substitution for cement at a percentage of 10% and added to no-fine concrete mix with 10% recycled aggregate. The results show that using 10% silica fume and 0.5% polypropylene fiber with 10% recycled aggregate increased the splitting tensile strength, flexural strength, compressive strength, and modulus of elasticity by (22.54 and 40.32%), (22.22 and 35%), (21 and 35.37%), and (22 and 38.19%) compared to reference mix (NC) and the no-fine concrete mix with 10% recycled aggregate (RNC10), respectively. In comparison, the dry density was higher by (1.34%) than RNC10 and lower by (0.68%) than NC.