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Bitumen aging increases the risk of pavement cracking. A good understanding of this phenomenon is crucial for designing long-lasting pavements. In this context, this paper presents a review of the relevant literature on neat bitumen aging. A broad set of indexes often used to estimate the aging level and end-of-life criteria of bitumen are analyzed and discussed.

The present paper describes the rutting behavior of innovative mixes incorporating 50% of Reclaimed Asphalt (RA) with bio-materials. They were assessed in the laboratory and in a full-scale accelerated experiment. The innovative mixes studied here contained bio-materials especially designed to help recycling by re-activating the aged binder from RA. Four mixes were evaluated: three of them are manufactured with bio-materials, (two bio-rejuvenators and one bio-binder) and one was a control mix, which was a high modulus asphalt mix (EME2). In this study, the rutting resistance of the four mixes was first evaluated in the laboratory with both European and US methods. The full-scale test was then performed in order to evaluate the rutting resistance of the bio-recycled asphalt mixes under heavy traffic (200,000load cycles loaded at 65kN) and compared with the control one. A simplified analysis leads to the conclusion that, with the Nantes climate, a daily traffic of 150heavy vehicles per day applied over 20years corresponds to approximately 200,000heavy vehicle loads when the surface temperature exceeds 30°C. Therefore, it can be considered that the rutting evaluation made on the carrousel represented almost 20years of traffic during hot-day periods. The results obtained on the test track were consistent with the laboratory rutting tests showing good performance for all the mixes. The materials presenting the best performance on the test track also presented the best performance in the laboratory.

Nowadays, the development of electric heavy goods vehicles is hindered by the limited capacity of batteries. An alternative solution to batteries is to develop electrified road systems, capable of supplying and/or recharging electric vehicles while they are driving. In this project, an Electric Road System (ERS), i.e. a solution for electric supply by a feeding track embedded in the pavement, is studied. The system consists of metallic conductive segments, fixed on a rubber support, installed in a groove in the middle of the pavement. Laying such a device in a bituminous pavement requires an efficient bonding of the rubber with the pavement materials, and a good resistance to traffic and climate. Studies were made at laboratory scale and at full scale to select appropriate joint materials and assess the load resistance and durability of the rail/pavement system. Two types of laboratory tests were performed on asphalt concrete samples integrating the rubber elements: wheel tracking tests, at temperatures of 20, 40 and 60 °C, and climatic tests (temperature cycles between −20 °C and 20 °C). Modelling of the tests was also carried out. After evaluation of different products, an appropriate joint material was selected. Then, an accelerated test was performed with the FABAC traffic simulator, to validate the behavior of the electric supply system inserted in a bituminous pavement, at full scale. The pavement structure was instrumented, submitted to 500 000 dual wheel load cycles at 65 kN, and monitored using deflection measurements and profile measurements. The test confirmed the satisfactory behavior obtained at laboratory scale.

This volume gathers the latest advances, innovations, and applications in the field of accelerated pavement testing (APT), presented at the 6th International Conference on Accelerated Pavement Testing, in Nantes, France, on September 27-29, 2021. Discussing APT, which involves rapid testing of full-scale pavement constructions for structural deterioration, the book covers topics such as APT facilities, APT of asphalt concrete and sustainable/innovative materials, APT for airfield pavements, testing of maintenance and rehabilitation solutions, testing of smart and multi-functional pavements, data analysis and modeling, monitoring and non-destructive testing, and efficient means of calibrating/developing pavement design methods. Featuring peer-reviewed contributions by leading international researchers and engineers, the book is a timely and highly relevant resource for materials scientists and engineers interested in determining the performance of pavement structures during their service life (10+ years) in a few weeks or months.

Pervious concrete use has increased since more than a decade thanks to its main feature of high water permeability. However the use of this material is still limited to light traffic areas, like car parks or walkways in urban areas. Recently LafargeHolcim Research Center has developed an innovative concept of concrete pavement structure using this type of material for heavy traffic highways. An ultra-thin innovative pervious concrete layer is laid directly (wet on wet) on top of an optimized concrete layer just after its placement. This innovative solution allows ensuring both structural performance and surface characteristics for road users in terms of safety, riding comfort and aesthetic. In order to evaluate the actual performance of this innovative pavement structure, an accelerated pavement test (APT) was carried out using the FABAC heavy traffic simulator of IFSTTAR in Nantes. A total of five million cycles of 6.5 tons half-axle load were applied. Structural performance and lifetime of the pavement were evaluated by comparison with a design process using the French-standard-design-software called Alize-LCPC. The evaluation of the bonding strength at the interface between the pervious wearing course and the structural concrete bottom layer showed good durability throughout the entire test, which could allow possible consideration of the surface layer in the whole pavement design process. Finally, dynamic friction tests conducted on the innovative wearing course during the APT allowed to evaluate and predict the evolution of its skid resistance throughout the pavement lifetime.

The present paper describes the full-scale accelerated test, carried out on asphalt pavements made up with bio-materials, especially designed to help reusing Reclaimed Asphalt (RA) by re-activating the aged binder. Four pavement sections were evaluated: three pavement sections with innovative bio-materials (bio-recycled asphalt mixtures), and a reference section with a conventional, high modulus asphalt mix (EME2). In this study, fatigue resistance was first evaluated in laboratory, with two-points bending test, and then at full scale under heavy traffic loading, with the IFSTTAR accelerated pavement testing facility. The evolution of bio-materials recycled asphalt mixture characteristics, as well as the pavement distresses, were recorded and analyzed. The structural condition of the pavement sections was monitored periodically through falling weight deflectometer (FWD) measurement as well as with strain gauges and temperature sensors. Although the reference EME2 mix presented the highest fatigue resistance in laboratory, on the full scale test, the three bio-based asphalt mixtures performed similarly or better than the control EME2 mixture.

The aim of this study is to develop a method for identifying asphalt pavement layer properties based on readings from accelerometers and geophones that are embedded near the ride surface. These sensors are relatively small in size and easily embeddable, making them an ideal choice for wide-area applications in the live transportation network. As a first step, a section within the IFSTTAR accelerated pavement testing (APT) facility was instrumented with accelerometers and geophones; also installed was an anchored displacement sensor to serve as a reference/validation device. The APT facility offers the ability to control the loading configuration and intensity, travel speed, and wander (i.e., lateral offset) position relative to the sensor locations. Thus, it becomes possible to isolate the task of property identification through inverse analysis from other real-world complications. The paper commences by describing the experimental setup, and presenting some raw sensor measurements during a single pass of the APT’s wheel carriage. Then, assuming a layered-elastic model, a method is proposed and demonstrated for estimating the pavement moduli. The method is based on best-matching measured velocities and accelerations for the geophones and accelerometers (respectively), with the model predictions- without integrating the signals to convert them into deflections. Very good match is obtained for the sensor readings, and the inferred moduli closely agree with reference values. This outcome means that there is great potential in building a pavement condition monitoring system with near-surface accelerometers and geophones.

In accelerated pavement tests performed at IFSTTAR, it is common to perform continuous deflection measurements under applied loading, using deflection sensors. These sensors, which consist of an LVDT attached to a rod anchored at a depth of about 4 m, are difficult to install and relatively expensive. In this project, the possibility of using geophones or accelerometers, as an alternative method to measure pavement deflections has been investigated. Geophones and accelerometers measure respectively the vertical velocity and the vertical acceleration, and by integrating their signals, it is possible to calculate the deflection. Two types of geophones, and two types of accelerometers have been selected for the study. They have first been submitted to laboratory tests, on a vibrating table, simulating pavement deflections signals. Based on these tests, suitable signal treatment methodologies, to filter and integrate the signals, to obtain reliable deflection measurements, have been developed. The sensors have then been installed in an experimental pavement section, tested on the IFSTTAR APT facility. Deflections obtained with the geophones and accelerometers have been measured under different load conditions. The obtained values were in good agreement with those measured with a reference deflection sensor.

Accelerated pavement testing (APT) is well known as a very effective way to investigate the actual behaviour of pavement structures. Feedback from the test can be obtained in a couple of months through measurements and monitoring made during the experiment. Among them, pavement surface cracking is one of the most important parameters for the evaluation of experimental pavement performance. Generally, crack monitoring during APT tests is still carried out manually for every specific loading period. This classical approach is time-consuming and interesting information may be lost if a measurement is missed. For this reason, a Rapid and Continuous Imaging (RCI) technique has been developed and tested at IFSTTAR, for the monitoring of crack development on the pavement surface during APT experiments. The principle of this technique consists in taking images of the experimental pavement surface continuously along the test track, at intervals depending on the moving speed of the heavy traffic simulator, i.e. the road fatigue carrousel. A crack map, representing an overview of visible cracks on a pavement section can then be rapidly created using an ad hoc image processing tool. The application of this pavement crack mapping technique for crack monitoring on an asphalt pavement during a recent APT experiment showed interesting results.

Road construction companies are developing innovative road solutions which integrate new functions, such as the ability to generate energy. The authors focus here on the use of road solutions harvesting solar and geothermal heat energy. In 2014, PIARC’s report entitled “Alternative solutions for fossil fuels for the road system” listed the main limitations blocking the development of these innovations among which the resistance to traffic. The authors present a recent accelerated test at scale one of a pavement that incorporates geothermal tube networks in the first 10 cm of the pavement. The main goal is to assess the impact of the tubes on the durability of the overlay and structure. The first part of the paper describes the experimental site, located at the toll station of Saint Arnoult, next to the A10 highway, near Paris. It is composed of 4 trial sections. Tubes were buried at construction stage at 2 different depths. The second part presents the experimental setup: (i) the FABAC traffic simulator used for the tests and (ii) the survey methods used to follow the evolution of the structures. The third part present the measurements made during the tests and the fourth part is dedicated to the analysis of the results and conclusions.

Recently, the French motorway company Cofiroute has decided to reconstruct the slow lane of a section of the motorway A10, located west of Paris. This section supports a very heavy traffic, of about 4000 trucks/day (corresponding to 4800 french standard equivalent 130 kN axle loads). The solution adopted for the reconstruction consists in retreating in situ, with a hydraulic binder, the existing bituminous subbase, and adding new base and surface layers, incorporating 30 % of recycled materials from the old pavement. To validate this novel solution, and in particular the in situ retreatment, Cofiroute asked IFSTTAR (the French Institute of Science and Technology for Transport, Development and Networks) to instrument this pavement structure. Four sections were instrumented with classical strain gage sensors, placed at different levels in the pavement (subgrade, treated subbase, bituminous base), and temperature sensors. On a fifth section, a more innovative instrumentation, including geophones, crack opening sensors, and temperature sensors was installed, associated with a remote data acquisition system. The instrumentation was installed during construction, in November 2011, and most transducers are still functioning. The paper presents the monitoring of these experimental sections. The strain gage measurements were used to fit a mechanical model of the pavement structure, and to evaluate the modulus of the different pavement layers, and their evolution with time. The results confirmed the good performance of the in situ retreated subbase, and validated the technical choice of the road owner. The geophones are very sensitive sensors, which measure vertical displacement velocity. Different methods of treatment of the geophone measurements were proposed, to monitor pavement deflections, and also to identify and classify truck silhouettes, and estimate truck loads.

This paper presents an experiment, performed on the IFSTTAR circular accelerated testing facility, to evaluate the performance of different weight in motion (WIM) sensors. This project, carried out with the French ministry of transport, aims at improving the performance of these WIM sensors, to allow automated overload control. Four different types of sensors were evaluated in the project: piezo-quartz sensors (2 types), piezo-ceramic sensors and piezo-polymer sensors. The full scale experiment was performed on a thick bituminous pavement. A total of 10 WIM sensors were installed, as well as other sensors (temperature probes, vertical displacement transducers, geophones). Accelerometers were also used to monitor dynamic load variations. The response of the sensors was evaluated under a wide variety of loading conditions (different loading speeds, temperatures and lateral positions of the wheels). In the first phase of the experiment, the 4 arms of the carrousel were all equipped with single wheels (with wheel loads of 45 or 55 kN). In a second phase, different wheel configurations were tested, on each arm of the testing facility (single wheel, dual wheels, tandem, tridem). A large database, of about 30000 WIM signals, was collected. The full scale tests have allowed to evaluate the repeatability of the different types of sensors, and the influence of different loading conditions (temperature, load type, loading speed..). The results indicate that the sensitivity of the different types of transducers to loading conditions is very different. Recommendations for correcting and improving WIM sensor response have been made.