Ageing is among the most prevalent causes of hardening in bituminous pavements. Under the effect of traffic loads, this hardening induces the formation of micro-cracks, which then evolve into macrocracks and ultimately lead to pavement failure. However, it remains challenging to assess the extent of micro-cracking within a specimen. This paper presents two methodologies for generating controlled micro-cracks in laboratory: either through classical fatigue testing after a certain number of cycles or by a new method proposed in this paper of incorporating PTFE pellets into the loose bituminous mixture prior to compaction. Due to their low adhesion to other materials, these pellets act as artificial defects within the bituminous mix, mimicking the presence of cracks. Complex modulus tests were then conducted on both aged and unaged, undamaged materials, while creep-recovery tensile tests were performed on micro-cracked specimens. A micromechanical modelling approach was then developed and initially validated on the behaviour of undamaged materials before being employed to simulate the response of PTFE-treated or fatigue-damaged specimens. This modelling framework enables the evaluation of micro-crack density in damaged bituminous specimens. The results show a strong agreement between the experimental creep-recovery curves and the expected behaviour of PTFE-treated specimens, where the predetermined crack density of 0.2 is set by the amount of PTFE incorporated into the loose mix prior to compaction. For fatigue-damaged specimens, where the crack density is unknown, this parameter is adjusted within the micromechanical model. For specimens subjected to fatigue damage after 60 000 loading cycles, the creep-recovery test modelling yielded an estimated crack density of 0.15.

This study investigates the viscoelastic behavior of asphalt concrete slabs subjected to rolling wheel loading using a combination of laboratory testing and finite element modeling. The work is motivated by the limitations of the French Wheel Tracking Test (FWTT), which, while widely used to evaluate rutting resistance, does not fully capture the evolution of strain fields under realistic traffic conditions. Experimental tests were conducted on asphalt slabs placed over a soft rubber foundation to reproduce in-situ deflections of low-traffic pavements. Strain and displacement fields were measured with a contactless optical system under varying temperatures and loading speeds. In parallel, a three-dimensional finite element model was developed in LMGC90, integrating tire–pavement contact stresses obtained from sensor measurements. The material behavior was described using the Nonlinear Viscoelastic (VENoL) model, calibrated with complex modulus tests. The simulations reproduced longitudinal, vertical, and shear strains as well as slab deflections with good agreement to experimental data. Results highlight the influence of temperature and speed on viscoelastic response, with shear strains identified as key contributors to rutting and cracking. Overall, the Finite Element Method (FEM)–VENoL approach provides a reliable framework for predicting pavement performance and understanding degradation mechanisms. Future work will extend this methodology to multilayer asphalt systems to study interlayer interactions.

The purpose of this paper is to investigate the fatigue behaviour of bio-binders using a uniaxial tension-compression test. Three 50/70 binders were selected: an unmodified bitumen (B0) as reference, a partially bio-based binder with 8

Bituminous mixtures are viscoelastic granular materials whose behavior under repeated loading is governed by both loading speed and interlayer bonding. In this study, the response of bilayer asphalt slabs under moving tire loads was investigated through combined experimental and numerical approaches. French Wheel Tracking Tests (FWTT) were performed at 20 °C and for three loading speeds (0.7, 3.5, and 7.0 km/h) with a tack coat, and at 50 °C and 3.5 km/h for two additional tests conducted with and without a tack coat. A discrete element approach (DEM), based on the Contact Dynamics (CD) method and implemented in LMGC90, was developed to reproduce the bilayer slab behavior. Increasing speed reduces both vertical and horizontal displacements, while the tack coat enhances interlayer adhesion and structural continuity. Compared with the experimental responses, the numerical analysis predicts displacement, with associated relative error ranging from 0.92

Ageing is a major cause of bituminous pavement hardening and premature degradation. This study evaluates the effect of laboratory ageing on the viscoelastic properties of bituminous mixes through time and frequency domain characterisation and physicochemical analysis. Three thermo-oxidative ageing durations (0, 4 and 9 days) were considered. RTFOT and PAV tests were conducted on fresh bitumen, followed by FTIR and asphaltene content analysis. Tensile creep-recovery and complex modulus tests characterised aged and unaged mixes. The Huet-Sayegh and Generalised Maxwell models were used to simulate axial strain evolution. The results show that stiffness moduli increase with ageing. Rheological parameters (R-value, Ec) correlated with ageing duration. Creep compliance decreased over time, with a strong correlation between steady-state creep viscosity (eta 0) and the combined ageing index (ICO + ISO) across all tested temperatures.

In this study, an experimental campaign of the French wheel tracking test (FWTT) and numerical modelling using a discrete element approach based on the Contact Dynamics (CD) method were performed to analyse the response of bituminous mixtures to moving tyre loads. A coupling chain models the interaction between the slab surface and the moving tyre, reproducing numerically measured footprint. The moving load applied over the textured surface generates heterogeneous forces on the particles in the bituminous slab, which are influenced by the non-uniform distribution of particle sizes and their bearing capacities. The study shows also that temperature has significant effects on the behaviour of the bituminous mixture, with high temperatures causing significant permanent displacements and irreversible deformations of the bituminous slab. This validation of the coupling model highlights the complexity of interactions. Furthermore, it offers a comprehensive investigation with detailed information on the movement and kinematics of the particles.

We present some preliminary results of a national research project dealing with the wearing course damage and the tire-pavement interactions with traffic loadings, where asphalt concrete raveling test and its modelling are ongoing studies. For this, we used the Local Fracture Test (LFT) or the French acronym RULOB test, developed by Gustave Eiffel University, to analyse the fracture behaviour of bitumen and mastic. The test reproduced a film of binder placed between two aggregates under defined loading conditions. The results of the test highlighted the influence of the loading conditions on the failure scenarios encountered, and the different ageing conditions (RTFOT, RTFOT+PAV). The role of filler in the bitumen (mastic) is also investigated in the same way. The study also attempted to reproduce the experimental test using the DEM software LMGC90. The results agree with the next step of our ongoing study which is to model ravelling tests of asphalt concrete.

The experimental investigation focuses on evaluating fracture properties of asphalt binders at low temperatures through the Local Fracture Test. The test consists in subjecting a thin film of binder to controlled tensile loads, simulating the response of the material inside the pavement. The methodology adopted combines laboratory measurements and FEM simulation. The model describes the theoretical response of the sample when a crack of variable size appears, integrating linear viscoelasticity and sample geometry. Different materials are compared, based on their fracture energy determined from the force-displacement curves. A specific criterion is proposed to determine the critical fracture temperature for each binder. Outcomes showed the effectiveness of the adopted methodology in evaluating the fracture properties of investigated materials. Moreover, a high correlation between the critical temperatures derived from the Local Fracture Test and the glass transition temperatures coming from Dynamic Mechanical Analysis was found for the unmodified binders.

This paper presents part of the studies developed in the European project ENSEMBLE. (ENabling SafE Multi-Brand pLatooning for Europe). The first part of the paper describes the validation of a numerical model based on comparisons with experimental results obtained from a test section subjected to the pass of 3 human-driven trucks simulating a platoon configuration. The numerical model is then used to predict the maximum and accumulated strains produced by the passage of each truck on the same test section at two different temperatures when the following platoon parameters are varied: (1) inter-truck time gap, (2) truck speed and (3) lateral deviation (wandering). The results confirm that the proper control of these parameters can help to keep the same level of fatigue damage as with trucks in individual configurations. In this way, the environmental, social and economic benefits of platooning can be attained without compromising the existing pavement structures.

The primary purpose of a pavement is to distribute the load generated by traffic across its various layers. To better understand the effects of tire-pavement interaction, the FWTT (French Wheel Tracking Tester) laboratory test is conducted. In this research, our objective is to develop a three-dimensional numerical model that closely fits the FWTT test conditions and provides comparable strains and displacements fields with the experiment. The model will accurately represent the wheel footprint geometry and pressure, identified using TekScan device, and replicate the same configuration as the test. Instead of applying incremental loading, the wheel’s movement over the specimen will be simulated using real vertical and horizontal forces. These unique characteristics of the model distinguish our research from previous studies. The current model, based on the finite element method, utilizes LMGC90 software and incorporates a viscoelastic constitutive model. The results obtained from the model demonstrate the agreement with the vertical displacement measurement, as well as the vertical and longitudinal strains.

This chapter presents some results of an investigation of the durability of surface layers of asphalt pavements subjected to traffic and frost-thaw cycles using experimental data from large-scale heavy vehicle tests and finite element modeling. The tested pavement is composed of two asphalt layers. The test sequences are carried out under dry and partially saturated conditions for these layers. The focus of this chapter is limited to the analysis of the response of the pavement structure under thermal loading; the response to mechanical loading is not addressed. During the test, high levels of water content in the asphalt materials are reached, and the development of swelling strains in the partially saturated layers, due to phase change of pore water, is clearly evidenced. The swelling strain magnitude in the partially saturated asphalt concrete material is determined through simulation of the test. Moreover, the comparison between the gage measurements obtained under dry and partially saturated conditions shows that a consequence of frost in asphalt concrete is the development of differential horizontal strains between the layers. To reproduce this effect in the simulation, bonding between the asphalt layers must be relaxed reflecting the fact that, in some way, the interface is significantly stressed out what could be detrimental to it.

•Experimental and numerical study to evaluate the initial response of surface asphalt layers to traffic loading and varying temperature conditions.•In newly reinforced pavements, interfaces between pavement layers can exhibit some sliding, particularly for structures with tack coat.•A thin elastic layer can significantly enhance predictions.•Temperature gradients improved the viscoelastic model's ability to predict pavement strains.•The temperature gradients resulting in reduced tensile strains with depth.•Small changes in thickness of the surface layer can significantly affect the strain at the bottom of the layer, particularly at high pavement temperatures.

Partially/fully self-driven trucks in platoon configurations promise to increase transport efficiency, reduce fuel consumption/gas emissions and improve road safety through the use of connectivity technologies and automated driving support systems. However, truck platooning means the introduction of new types of loads on pavements which are characterised by: multiple loads, generated by the multi-axle configurations of the different trucks forming the platoon, traffic channelisation by the reduction of the lateral deviation of the trucks, and reduced inter-truck time gaps, which may reduce the self-recovery capacity of asphalt concrete materials, reducing the pavement service life. In this context, this study presents a parametric analysis carried out to evaluate a pavement structure subjected to several platoon truck configurations. The results of the study indicated that to keep the same pavement structural response as for individual trucks, it is possible to act on the following parameters in the platoon configuration: traffic distribution along the year and along the time of the day (avoiding traffic at higher temperatures), percentage of platoon penetration in the daily and annual traffic, level of loading of the trucks, number of trucks in platoon configuration, wandering, and inter-truck time-gaps/distances.

Fracture of viscoelastic materials is considered to be a complex phenomenon due to their highly rate sensitive behavior. In this context, we are interested in the quasi-static response of a viscoelastic solid subjected to damage. This paper outlines a new incremental variational based approach and its computational implementation to model damage in viscoelastic solids. The variational formalism allows us to embed the local constitutive equations into a global incremental potential, the minimization of which provides the solution to the mechanical problem. Softening damage models in their local form are known to result in spurious mesh-sensitive results, and hence, non-locality (or regularization) has to be introduced to preserve the mathematical relevance of the problem. In the present paper, we consider two different regularization techniques for the viscoelastic damage model: a particular phase-field and a lip-field approach. The model parameters are calibrated to obtain some equivalence between both these approaches. Numerical results are then presented for the bidimensional case and both these approaches compare well. Numerical results also demonstrate the ability of the model to qualitatively represent the typical rate-dependent behaviour of the viscoelastic materials. Besides, the novelty of the present work also lies in the use of lip-field approach for the first time in a viscoelastic context.

Truck platooning is a recent solution proposed to optimise road transportation. Platooning can help improve transport efficiency and road safety, reduce traffic congestion, fuel consumption and greenhouse gases emissions. Considering that truck platoon configurations are new, studying their impact on pavement response and damage is crucial. In this context, this study presents the results obtained in a full-scale experiment designed to evaluate the structural responses of a test track subjected to the pass of trucks under two configurations: individual and platoon. The pavement was instrumented to measure the transverse and longitudinal strains at the bottom of the asphalt layers of the pavement structure. Strains were measured under two test configurations, individual trucks and platoons, for four vehicle speeds: 40 , 60 , 70 , and 80 km/h. In order to consider the weather influence, two test campaigns were performed, one during the winter and the other during the summer. The study's main conclusion is that by managing inter-truck distances, truck speeds, lateral deviation (wandering), time, and periods of circulation, it is possible to minimise the impact of platooning trucks on the pavement's structure responses.

This article aims at presenting a thermo-mechanical model dedicated to fatigue cracking in bituminous material. The model calibration based on two-point bending (2PB) fatigue tests performed on specimens of bitumen-bound sand is also detailed. In the model, crack growth is handled by the Paris law considering the initialization term Nini. This parameter represents the number of loading cycles required to initiate a short macrocrack of length a0 from which the Paris law can be applied. The tests utilized for calibration and comparison with the numerical simulations are performed on notched and unnotched trapezoidal samples, for different levels of imposed displacement amplitude. The parameters of the Paris law are determined using the notched specimens (a0 being assimilated to the notch depth) except for Nini, which is deduced from the difference in lifetime duration between the tests carried out on notched and unnotched specimens. The full calibration procedure described thereafter has the advantage to not depend on the choice of a0. It is shown that the simulations run for the calibrated model are globally in good agreement with the test results obtained for both types of samples and for all the imposed displacement amplitudes. Finally, the model is used to predict the response of four-point bending tests carried out on the same bitumen-bound sand, considering the input parameters determined from the 2PB tests. The intrinsic nature of the model is evaluated through its ability to simulate both types of tests using the same set of material parameters.

Truck platooning for the transportation of loads is a strategy recently proposed by the automotive sector to cope with traffic congestion, fuel consumption, and operational costs. This new way of configuring trucks changes the typical pressures pavements structures experience. For this reason, the research efforts of the pavement sector should be aligned with the automotive sector to propose road-friendly platoon configurations. This is one of the objectives of the European project ENSEMBLE. ENSEMBLE, as indicated by its acronym, works on ENabling SafE Multi-Brand pLatooning for Europe. In this context, the present study presents a real scale test done in the Applus IDIADA facilities to evaluate the fatigue behavior of a pavement structure subjected to individual and platoon truck configurations. The effects of parameters such as traffic distribution through the year and by time of day, percentage of platoons, truck loads, number of trucks in platoon configuration, lateral wandering, and inter-truck distances were evaluated. The study’s findings revealed that the reduced rest times between trucks in the platoon configuration reduce the recovery time of the asphalt layers, increasing the fatigue damage to the pavement at high temperature conditions. This underlines the need for further research to allow the proper implementation of truck platoons. For example, research is needed to define strategies to make truck platoon configurations more pavement-friendly and analyze the costs associated with the changes in the required road maintenance/rehabilitation treatments, among others.