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This paper presents an Acoustic Emission characterisation of the damage behaviour of asphalt concrete subjected to bending fatigue loading. An experimental campaign is carried out on an old asphalt...

Bitumen aging has long been recognised as one of the primary factors that affect pavement’s durability. The amount of rheology-based indexes proposed to track the evolution of bitumen aging level u...

The objective of this study is to assess the impact of climate on the performance of bituminous pavements with two different methods, and then to examine their impact on actual design scenarios. Three climate cases were selected for the comparisons involving the effect of temperature: one in France (Bordeaux) and two in the United States (Seattle and Phoenix). The case of an experimental site in Québec was also used for comparisons concerning consideration for seasonal variations in ground bearing capacity. The analyses were based on French (Alizé-LCPC) and US (AASHTOWare Pavement ME Design) mechanistic-empirical pavement design approaches. Interesting features of the two design methods are outlined and their fatigue cracking models are linked together. The results of the study highlight the importance, for design purposes, of the empirical fatigue equations as a function of temperature. For the site studied in France, the design results in terms of AC base layer thicknesses indicate that both methods show a similar trend with an increase in temperature. For the site in Québec, which is submitted to severe freeze/thaw cycles, the results show that taking temperature and moisture into account for unbound materials leads to a prediction of more severe permanent deformation.

Pavement instrumentation has recently become an important aid-tool of pavement monitoring for the assessment of pavement structural behaviour. Classically, measurements on instrumented pavements are performed on site, under known load conditions: the response of the pavement is recorded under the passage of a reference vehicle, with known axle loads. In such conditions, data interpretation and modelling of the pavement are relatively easy. However, on site measurements are time consuming and costly to perform, because they require using a dedicated vehicle, and closing the lane to traffic, which is not easy on a heavily trafficked motorway. This paper presents an experiment, where an instrumented bituminous pavement motorway section has been followed by remote monitoring, under normal traffic. The section, instrumented with strain gages, temperature probes and geophones, has been monitored continuously during 18 months. Signal sorting procedures have been developed for reducing the quantity of recorded data, and for analysing the structural response of the pavement, under highly variable loading conditions, and are presented and discussed. The results of the strain gage measurements, made at different depths within the pavement, have shown that the response of the pavement presents large variations with temperature, and in particular, that the degree of bonding between pavement layers can decreases at high temperatures, leading to sliding between pavement layers. The mechanical response of this instrumented pavement section has been analysed using a classical multi-layer linear elastic pavement model and also a viscoelastic model. The best predictions have been achieved with the viscoelastic model. Different approaches for describing the behaviour of pavement layer interfaces have also been evaluated.

A portion of the lane reserved for slow vehicles on a motorway was totally rebuild of the A10 Motorway in the West of Paris. Four sections have been instrumented using classical strain gage sensors, placed at different depths within the pavement (subgrade, cement-treated subbase, and bituminous base) and temperature sensors. A fifth section is equipped with a more innovative instrumentation including geophones and temperature sensors, coupled with a remote data acquisition system. The purpose of this paper is to present the monitoring of these experimental sections since 2011. Strain gage measurements are used to develop a mechanical model of the pavement structure, to evaluate the modulus of the different pavement layers, as well as their evolution with time. The results confirm the good performance of the inplace recycled subbase. Geophones are very sensitive sensors measuring vertical displacement velocity. Different methods for the processing of these measurements are proposed in order to monitor pavement deflections and identify and classify truck silhouettes.

Most European countries are active in the field of recycling road materials, but knowledge and practice differ between countries. The European project DIsmantling and RECycling Techniques for road MATerials - Sharing knowledge and practices aims at sharing knowledge and practice in this field among the 15 participating countries, with the view of drafting European best-practice guidelines. This paper reports on the first step towards this goal, which consists of summarising documented practices within these countries concerning demolition and recy- cling of road materials back into new unbound road layers. Common documented practice and major differences between European countries are highlighted and put in perspective, thanks to a broader international document review.

Reinforcement using an interlayer system has been demonstrated for more than four decades as a multi-purpose solution to improve performance, to extend service life and thus to reduce maintenance costs of road pavements. Among a large number of existing interlayer systems, glass fibre grids have shown effective use in pavement reinforcement with a hot mix asphalt overlay. Recently they have received increasing attention from the pavement community. However, as for other types of interlayer systems, the mechanisms underlying the effectiveness and proper installation of this type of reinforcement system are still not fully understood, and the choice of the most appropriate grid (e.g. mesh size, tensile strength) and its optimal location in the pavement system are mainly based on experience. This article presents firstly a literature review on the use of glass fibre grids in pavement reinforcement. Then some results of recent full-scale tests on the accelerated pavement testing facility of the IFSTTAR are presented. They confirm that glass fibre grid properly installed near the bottom of the asphalt layer improves significantly the fatigue life of the reinforced pavement. They also demonstrate the efficiency of glass grid use under only a thin asphalt overlay. Finally, first results obtained using an original instrumentation of glass grid strands by means of strain gages, to understand better the mechanical behaviour of the glass fibre reinforcement in a new pavement structure are described.

In order to study the permanent deformations of bituminous mixtures, a temperature-controlled triaxial test has been set up. By means of triaxial creep tests at imposed stress, the influence of different parameters on the behaviour of bituminous materials (confining pressure, deviatoric stress and temperature) has been investigated. A viscoelastic–viscoplastic model has been developed to simulate the creep tests and has shown good ability for simulating the test results.

Permanent deformations of unbound granular layers and soils, caused by unfavourable moisture conditions, are one of the most common mechanisms of deterioration of low traffic pavements, with unbound granular bases. The paper presents permanent deformation models, developed by LCPC and by the University of Limoges, for the prediction of permanent deformations of unbound granular materials: a simple empirical model and two elastoplasticity based models for cyclic loading: one of them is based on the time independent plasticity with kinematic hardening, and the second one on the shakedown theory. The model parameters have been determined with cyclic triaxial tests performed on a granular base course material, at different moisture contents. An application of the models to finite element calculation of permanent deformations in a pavement structure is presented.