Asphalt Pavement Systems Research Articles

Design, construction, and evaluation of energy-harvesting asphalt pavement systems

Energy-harvesting pavements, one of which is the Hydronic Asphalt Pavement (HAP) system, have been proven to be both more durable and sustainable than conventional pavement systems. A HAP consists of a system of connected pipes embedded within the asphalt pavement which function to extract or reject heat from/into the pavement via a circulating fluid. Three large-scale systems were designed and constructed in the field: a control section, a regular HAP section, and a section containing a HAP coupled to a horizontal ground heat exchanger (GCHAP). The field data showed that neither the HAP section nor the GCHAP section were able to substantially decrease the pavement surface temperature. However, both GCHAP and HAP were able to decrease the asphalt temperature at a depth of 2.5 cm below the surface by a magnitude of around 10°C. Another key finding of this study shows that increasing the conductivity of a flexible pavement asphalt layer, rather than increasing the conductivity of the embedded pipes, significantly enhances the effectiveness of the HAP system.

Using Pavements to Generate Electricity

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.

The Influence of Geotextile Type and Position in a Porous Asphalt Pavement System on Pb (II) Removal from Stormwater

Porous asphalt (PA) pavement systems with and without a geotextile layer were investigated in laboratory experiments to determine the impacts of the geotextile layer on the processes leading to lead ion (Pb2+) removal from stormwater runoff. Two types of geotextile membranes that were placed separately at upper and lower levels within the PA systems were tested in an artificial rainfall experiment while using synthetic rainwater. The effect of storage capacity within the system on Pb2+ removal was also investigated. Results indicated that the use of a geotextile layer resulted in a longer delay to the onset of effluent. The non-woven geotextile membrane that was placed below the reservoir course improved the Pb2+ removal rate by 20% over the removal efficiency of the system while using a woven geotextile placed just below the surface but before the choker course. Pb2+ ions were reduced by over 98% in the effluent after being held for 24 h in reservoir storage. Results suggest that temporary storage of stormwater in the reservoir course of a PA system is essential to improving Pb2+ ion removal capability.

CONSTRUCTABILITY STUDY OF ASPHALT PAVEMENTS INCORPORATING SHALLOW GEOTHERMAL ENERGY

The incorporation of geothermal energy in heating and electricity production has rapidly increased during the last three decades. This paper focuses on the use of shallow geothermal energy in asphalt pavement, herein called Ground Coupled Hydronic Asphalt Pavement (GCHAP) system. GCHAP consists of a series of pipes embedded within the asphalt layer coupled with another network of pipes embedded in the soil. A circulating fluid acts to exchange the heat energy between the soil and the asphalt layer. The system can be used for cooling the pavement, which results in decreasing permanent deformation in the summer. This paper presents a study on the constructability and performance of such systems on a large-scale section. Numerical analyses and a pilot study were conducted to select the system design components. A 9.6 x 4 meter GCHAP section was constructed on a municipal road in addition to another control section. The secondary network of pipes was placed three meters below the ground. Sensors were embedded within the GCHAP system to record and compare the temperature of the pavement to that of the control section. The results showed that GCHAP section can decrease the pavement temperature leading to an increase in resistance to permanent deformation. Moreover, the constructability study showed the importance of performing a pilot study before constructing the system to ensure the resilience of the pipes.

The compartmented alginate fibres optimisation for bitumen rejuvenator encapsulation

This article presents development of a novel self-healing technology for asphalt pavements, where asphalt binder rejuvenator is encapsulated within the compartmented alginate fibres. The key objective of the study was to optimise the compartmented alginate fibre design, i.e., maximising amount of rejuvenator encapsulated within the fibre. The results demonstrate that optimum rejuvenator content in the alginate fibre is of 70:30 rejuvenator/alginate ratio. The fibres are of sufficient thermal and mechanical strength to survive harsh asphalt mixing and compaction processes. Furthermore, results illustrate that zeer open asfalt beton (ZOAB) asphalt mix containing 5% of 70:30 rejuvenator/alginate ratio compartmented alginate fibres has higher strength, stiffness and better healing properties in comparison to the control asphalt mix, i.e., mix without fibres, and mix containing fibres with lower rejuvenator content. These results show that compartmented alginate fibres encapsulating bitumen rejuvenator present a promising new approach for the development of self-healing asphalt pavement systems.

An Evaluation of the Efficiency of Compartmented Alginate Fibres Encapsulating a Rejuvenator as an Asphalt Pavement Healing System

This paper explores the potential methods for evaluating a healing system for asphalt pavements. The healing system under investigation involves compartmented calcium-alginate fibres encapsulating an asphalt binder healing agent (rejuvenator). This system presents a novel method of incorporating rejuvenators into asphalt pavement mixtures. The compartmented fibres are used to distribute the rejuvenator throughout the pavement mixture, thereby overcoming some of the problems associated with alternate asphalt pavement healing methods, i.e., spherical capsules and hollow fibres. The asphalt healing efficiency methods to be evaluated in this paper include: (i) standard test methods for asphalt pavements, such as the Indirect Tensile Strength test and the 4 Point Bending Fatigue test; and (ii) alternative fracture tests such as the Semi Circular Bend test. The study employs fracture theory in order to evaluate the efficiency of the damage repair. The research findings demonstrate that including compartmented calcium-alginate fibres encapsulating a rejuvenator into an asphalt pavement mix does not significantly improve the healing properties of the asphalt pavement. Nevertheless, the findings indicate that, with further enhancement, compartmented calcium alginate fibres may present a promising new approach for the development of self-healing asphalt pavement systems. Additionally, the test results indicate that the 4 point bend fatigue test is the most suitable test for evaluating the performance of self healing asphalt pavements.

Mechanical performance of concrete pavement reinforced by CFRP grids for bridge deck applications

Abstract In this paper we develop and investigate a novel composite bridge deck (CPCG deck) formed by a steel fibre reinforced concrete (SFRC) pavement reinforced by carbon fibre reinforced polymer (CFRP) grids. This approach may mitigate damage in traditional asphalt pavement systems and in cracking of steel deck plates as observed in existing orthotropic steel bridges. An experimental study of CPCG decks subjected to four-point bending is presented considering different locations of CFRP grids in the depth direction. Two groups of CPCG decks are fabricated and tested to investigate their mechanical performance under positive and negative bending moments. A simplified theoretical model based on Timoshenko beam theory is proposed to predict the load deflection behaviour of the CPCG decks, and the section transformation method is used to calculate the stress distribution along the depth of the composite decks. The calculated results demonstrate good agreement with the experimental results. The results from parametric analysis further show that the best location of CFRP grids is in the horizontal direction of the pavement within the upper depth of the pavement. CFRP grids formed by SFRC can effectively increase the stiffness of steel deck plates. The effect has also been confirmed by Finite Element Analysis (FEA) using three-dimensional models.

The reinforcement and healing of asphalt mastic mixtures by rejuvenator encapsulation in alginate compartmented fibres

This paper explores the potential use of compartmented alginate fibres as a new method of incorporating rejuvenators into asphalt pavement mixtures. The compartmented fibres are employed to locally distribute the rejuvenator and to overcome the problems associated with spherical capsules and hollow fibres. The work presents proof of concept of the encapsulation process which involved embedding the fibres into the asphalt mastic mixture and the survival rate of fibres in the asphalt mixture. To prove the effectiveness of the alginate as a rejuvenator encapsulating material and to demonstrate its ability survive asphalt production process, the fibres containing the rejuvenator were prepared and subjected to thermogravimetric analysis and uniaxial tensile test. The test results demonstrated that fibres have suitable thermal and mechanical strength to survive the asphalt mixing and compaction process. The CT scan of an asphalt mortar mix containing fibres demonstrated that fibres are present in the mix in their full length, undamaged, providing confirmation that the fibres survived the asphalt production process. In order to investigate the fibres physiological properties and ability to release the rejuvenator into cracks in the asphalt mastic, the environmental scanning electron microscope and optical microscope analysis were employed. To prove its success as an asphalt healing system, compartmented alginate fibres containing rejuvenator were embedded in asphalt mastic mix. The three point bend tests were performed on the asphalt mastic test samples and the degree to which the samples began to self-heal in response was measured and quantified. The research findings indicate that alginate fibres present a promising new approach for the development of self-healing asphalt pavement systems.

Performance Evaluation of Lightweight Pavement via Geo-Centrifuge Tests

Abstract Asphalt pavements on soft soils are very common in many parts of Korea. These result in long periods of soft soil treatment, increased treatment costs, residual settlement of asphalt pavements, increased maintenance costs, and so forth. To overcome these problems, a new asphalt pavement system was studied, featuring a permeable asphalt surface, lightweight base concrete, and pile foundations. The first objective of the study was to evaluate the mix design properties of the permeable asphalt pavement, such as the Marshall stability, flow, air voids, and elastic modulus. The second objective of the study was to evaluate the mixing ratio of water, cement, sand, and the bubble foaming agent, as well as the compressible and flexural strength. The third objective of the study was to determine the number of pile foundations and the spacing of each pile. To verify the performance of lightweight pavement systems on soft soil, geo-centrifuge tests were conducted. The 1/30 reduced lightweight pavement system model was used, and a maximum 30 g of accelerated loading was applied to the pavement system. The kaolinite was used to simulate the highly soft soils at ocean or riverside areas. The settlement of the pavement system and the stress-strain relationship and load-displacement of the pile foundations were determined. From our limited study, the use of lightweight pavement systems on soft soils could be an alternative construction method on soft soils to reduce the challenges of conventional design and constructions.

Investigation on the Bending Fatigue and Shear Failure in Steel Bridge Deck Pavement Systems

Abstract Bridge deck pavement layers are prone to bending fatigue and shear failure because of the continuous vibration, the vertical instant impact, and horizontal dynamic shear effect from vehicles onto the pavement system. To ensure the durability of pavement systems, a typical pavement system on a steel bridge was studied through numerical simulation and laboratory tests. The maximum tensile stress at the bottom layer and the maximum interlayer shear stress of bridge deck pavement were obtained under different loading conditions in numerical simulations. Then direct shear tests were conducted to study the fatigue characteristics of bridge deck pavement materials and structure. Finally, the fatigue resistance of the asphalt pavement system was investigated under the typical traffic level in the northeast of China. This study is helpful to design steel bridge deck pavement systems with good bending fatigue and shear resistance.

Evaluation of 4.75-mm Nominal Maximum Aggregate Size (NMAS) Mixture Performance Characteristics to Effectively Implement Asphalt Pavement System

【PURPOSES : This study primarily focused on evaluating the performance characteristics of 4.75-mm nominal maximum aggregate size (NMAS) asphalt mixtures for their more effective implementation to a layered flexible pavement system. METHODS : The full-scale pavements in the FDOT's accelerated pavement testing (APT) program, including 4.75-mm mixtures at the top with different thicknesses and asphalt binder types, were considered for the faster and more realistic evaluation of the rutting performance. The results of superpave indirect tensile (IDT) tests and hot-mix asphalt fracture mechanics (HMA-FM) based model predictions were used for cracking performance assessments. RESULTS : The results indicated that the rutting performance of pavement structures with 4.75-mm mixtures may not be as good as to those with the typical 12.5-mm mixtures, and pavement rutting was primarily confined to the top layer of 4.75-mm mixtures. This was likely due to the relatively higher mixture instability and lower shear resistance compared to 12.5-mm mixtures. The energy ratio (ER) and HMA-FM based model performance prediction results showed a potential benefit of 4.75-mm mixtures in enhanced cracking resistance. CONCLUSIONS : In relation to their implementation, the best use of 4.75-mm mixtures seem to be as a surface course for low-traffic-volume applications. These mixtures can also be properly used as a preservation treatment that does not necessarily last as long as 12.5-mm NMAS structural mixes. It is recommended that adequate thicknesses and binder types be considered for the proper application of a 4.75-mm mixture in asphalt pavements to effectively resist both rutting and cracking.】

Influence of Pavement on Fatigue Performance of Urban Steel Box Girder Deck

Based on spatial finite element analysis method, the Influence of pavement on fatigue performance of orthotropic steel deck was analyzed in terms of pavement system, asphalt pavement stiffness. The result shows that compared with asphalt pavement system, RPC pavement system can not only obviously improve the stress condition of steel bridge deck, but also significantly extend the fatigue life of steel bridge panel; Increasing the stiffness of pavement layer can obviously reduce the stress amplitude of fatigue details, especially for direct contact with the pavement.

Probabilistic Modeling of Dynamic Modulus Master Curves for Hot-Mix Asphalt Mixtures

Since the introduction of the dynamic modulus E* concept in the recent Mechanistic–Empirical Pavement Design Guide, there has been considerable interest in establishing reliable prediction models for E*. An investigation of the effectiveness of commonly used predictive models shows that E* predictions exhibit significant scatter around the measured values, with percentage of errors reaching about 6200%. A need exists for characterizing the uncertainties that are inherent in E* to serve as input to any future robust reliability analysis that aims at properly determining the probability of unsatisfactory performance of asphalt pavement systems. The primary objective of this study was to present a probabilistic model that would allow the user to determine a priori probability distribution for E* given knowledge about temperature and frequency. The seven-parameter model was based on the sigmoidal function and the shift factor that related reduced frequency to real frequency and temperature. The model was calibrated on the basis of a well-known published database that included 7,400 laboratory measurements of E* for 346 asphalt mixes. Monte Carlo simulations were used to propagate the uncertainties in the seven model parameters and determine realistic estimates of the mean, coefficient of variation, and probability distribution of E* at different frequencies and temperatures. Results showed that E* could be modeled by using a lognormal distribution with a mean that was estimated from the mean values of the parameters and a coefficient of variation that varied from a minimum of 0.55 for high values of reduced frequency to a maximum of 1.55 for lower values of reduced frequency.

Experimental Evaluation of Shear Resistance of Improved Steel–Asphalt Interfaces

Although steel orthotropic deck is currently the most widely adopted solution for long-span bridges, the poor adhesion to the upper asphalt layers still represents a serious problem without a clear solution. In recent decades many techniques that involve the use of special bituminous bonding coats, reinforced asphalt membranes, net-reinforced steel deck surfaces, or epoxy asphalt binders have been applied, with varying results, to improve the level of adhesion of the asphalt pavement to the steel surface. In this experimental study, two such techniques were adopted to investigate the shear resistance of steel–asphalt pavement systems. The first technique used epoxy asphalt both as a bonding coat and as a binder of the upper asphalt layer, while the second technique involved the use of a reinforced asphalt membrane that was applied on the steel deck before overlaying with conventional hot-mix asphalt (HMA). The Ancona Shear Testing Research and Analysis shear test device was used to evaluate the shear resistance of different types of HMA–steel interfaces and to investigate the effects of temperature and normal stress. The results have been compared with the shear properties of bitumen-coated interfaces, studied in previous research. The results showed that epoxy asphalt guaranteed high performance regardless of the test temperature. However, the shear resistance of the system with the asphalt membrane was lower than with the epoxy asphalt, although it was higher than the resistance of bitumen-coated interfaces at high temperatures.

Inferring Pavement Properties using an Embedded Accelerometer

A high-end single-axis inertial sensor, capable of detecting minute accelerations, was embedded in an asphalt pavement system. A vehicle of known dimensions and overall weight was driven along a straight line, passing near the sensor's embedment location at constant speed. Measured accelerations were analyzed as means to infer the pavement layer properties. For this purpose, instead of double integrating the accelerometer data to arrive at deflections, the raw measurements were first smoothed and then matched against computed accelerations. Vehicle speed and weight distribution between front and rear axles were also backcalculated. The paper describes the experimental details, analysis method, and results.

Toughening characteristics of plastic fiber-reinforced hot-mix asphalt mixtures

With the performance limitation of a conventional hot-mix asphalt mixture, the structural integrity of that is highly needed to be enhanced to increase the fatigue life of the mixture. Various geosynthetic alternatives have been widely utilized, such as geogrid, geotextile, or geomembrane layers at the bottom the mixture or on the top of a subgrade to improve the structural integrity of a hot-mix asphalt pavement system. Although reinforcing effects of such interlayers has been reported with some improvements in hot-mix asphalt pavements’ performances, such as mitigating rut or delaying reflective cracks; however, such alternatives do not enhance toughness, tensile strength, or shear strength of the hot-mix asphalt mixture itself due to that the interlayers are usually installed in between two layers in a pavement system and those interlayers do not mix with hot-mix asphalt mixtures. A new plastic fiber-reinforced hot-mix asphalt mixture was proposed in this study to provide more enhanced structural integrity of the mixture not only at the bottom of the mixture but also within the mixture. The developed mixture in this study led to significant enhancements in phenomenological toughness and fatigue life of that at least 1.5 times higher than those for conventional hot-mix asphalt mixtures as resulting from indirect cyclic fatigue tests in loading-control modes and four-point bending beam tests in displacement-control modes.

Compact tension test for fracture characterization of thin bonded asphalt overlay systems at low temperature

Asphalt overlays provide an economical means for treating deteriorated pavements. Thin bonded overlay (TBO) systems have become popular options for pavement rehabilitation. In addition to functional improvements, these systems ensure a high degree of waterproofing benefits. Conventional asphalt concrete fracture tests were developed for pavements with homogeneous asphalt concrete mixtures, and typically their thicknesses exceed 50 mm (2 inch). The use of spray paver technology for construction of TBO leads to continuously varying asphalt binder content, up to approximately one-third of the layer thickness. Commonly utilized fracture test geometries for asphalt concrete include the single-edge notched beam, SEN[B], the disk-shaped compact tension, DC[T], and the semi-circular bend, SC[B]. The SEN[B] test geometry is not preferable for use in pavement systems due to difficulties in procuring beam samples from the field. Applications of the other established test geometries, the DC[T] and SC[B] tests, are limited because of the material nonhomogeneity caused by nonuniform distribution of asphalt binder and smaller as-constructed thicknesses of TBO, which are usually less than 25 mm (1 inch) for gap-graded and 50 mm (2 inch) for dense-graded hot mix asphalt (HMA) mixtures. Both the DC[T] and SC[B] tests simulate movement of the crack fronts in transverse or longitudinal directions in the pavement. Use of these tests on field-procured samples of TBO yields a crack front that encounters nonhomogeneous material through the specimen thickness. The crack moves perpendicular to the axis of material nonhomogeneity, which makes data interpretation and fundamental material fracture characterization challenging. In addition, the crack in the specimen is correlated to a crack channeling across the pavement width rather than a bottom-up or top-down direction, which is more desirable from the standpoint of coupling experimental results with currently available simulation models. This paper proposes a test procedure for fracture characterization of graded asphalt pavement systems that have significant material property gradients through their thicknesses. Suitable specimen geometry and testing procedures were developed using ASTM E399 and ASTM D7313-07b as a starting point. Laboratory tests were performed using an optimized compact tension, or C[T], test geometry for field cores as well as laboratory-fabricated composite specimens. Laboratory testing using the proposed procedure clearly showed distinction in the fracture characteristics for specimens prepared with varying material compositions. The capability of distinguishing different materials combined with stable crack growth makes the proposed testing procedure ideal for fracture characterization of thin and graded pavement systems. Statistical analysis of test data revealed that the proposed C[T] test procedure is capable of detecting differences in fracture energy results across a wide range of pavement systems and yields a low test variability. Finite element simulations of the test procedure further indicate the suitability of the test procedure as well as demonstrating a procedure for extraction of fundamental material properties.

Procedure for Making Paving Decisions with Cluster and Multicriteria Analysis

For many years, much research has been carried out to assess the affordability of paving a road. Now, increased construction and maintenance costs for traditional asphalt pavement systems have persuaded many civil administrations, regional councils, and agencies to replace pavement with gravel surfaces. Low-volume roads (LVRs), as they are presented in this paper, constitute a significant proportion of the total road network in Italy (around 80%) and in many other countries. Such infrastructures are vital parts of the road network, but their construction can have significant adverse effects on the environment. As a result, these roads must be well planned, well designed, well constructed, and properly maintained to create minimal adverse effects, to be cost-effective in the long term, and to have acceptable maintenance and repair costs. Limited resources often exist for LVRs, and a frequent question is whether to use paved or gravel surfaces. In many cases, the choice depends only on economic considerations, which must take maintenance costs into account. A complete procedure that applies cluster analysis and multicriteria analysis is presented for deciding whether to pave gravel road surfaces on the basis of different geometric, traffic, and environmental layouts.

Evaluation of Structural Integrity of Asphalt Pavement System from FWD Test Data Considering Modeling Errors

This study examines the structural integrity assessment technique used for the asphalt pavement system that considers the modeling errors introduced by material uncertainties. To this end, the artificial neural network is utilized to estimate the elastic modulus of soil layers by using the measured deflection data from the Falling Weight Deflectometer test. A wave analysis program for a multi-layered pavement system is developed based on the spectral element method for more accurate and faster calculation. The developed program is applied for the numerical simulation of the Falling Weight Deflectometer tests, specifically for the reliability analysis and the generation of training and testing patterns for the neural network. The effects of uncertainties in the material properties for modeling a given pavement system such as Poisson ratio and layer thickness are intensively investigated using the Monte Carlo Simulation. Results reveal that the amplitude of impact loads is most significant, followed by the layer thickness and the Poisson ratio, which are more significant on the max deflections than other parameters. The evaluation capability of the neural network is also investigated when the input data is corrupted by the modeling errors. It is found that the estimation results can be significantly deviated due to the modeling errors. To reduce the effect of the modeling error, (to improve the robustness of the algorithm), we proposed an alternative scheme in order to generate the training patterns taking into consideration any modeling errors. The study then concludes that the estimation results can be improved by using the proposed training patterns from an extensive numerical simulation study.

OSimulation and Characterization of Asphalt Pavement Temperatures

Characterization of pavement temperature, including, substantial analysis of measured asphalt temperature data from the MnROAD facility and simulations of pavement temperature using a one-dimensional finite difference heat transfer model are presented. The measured pavement temperatures are characterized at diurnal and seasonal time scales, including daily extreme temperatures, temperature gradients, diurnal cycling, and seasonal variations. The temperature simulations provide more detailed information on temperature gradients in the pavement and on the surface heat transfer components than the measurements, and also help to evaluate the quality of the pavement temperature and climate measurements. This information is critical in quantifying aging effects at the surface of asphalt pavements and in modeling the asphalt pavement system response to environmental and traffic loading.