Paul Marsac

Synthesis of standards and procedures for specimen preparation and in-field evaluation of cold-recycled asphalt mixtures

The use of recycled asphalt (RA) materials in pavement rehabilitation processes is continuously increasing as recycling techniques, such as cold recycling (CR), are being utilised in increasing magnitude and greater awareness for use of recycled materials and consideration of sustainable practices is becoming common in the construction industry. The focus of this paper is on developing a state of the art and state of the practice summary of processes used for classification of RA as well as the curing and specimen preparation practices for cold-recycled asphalt mixtures. A variety of topics were explored through an exhaustive literature search, these include RA production methods, definition of RA materials, stockpiling practices, industrial operations, specimen curing and preparation practices and in-field evaluation of cold-recycled rehabilitation. This paper was developed through efforts of CR task group (TG6) of RILEM Technical Committee on Testing and Characterization of Sustainable Innovative Bituminous Materials and Systems (TC-237 SIB).

Prediction of the Mechanical Properties of Aged Asphalt Mixes from FTIR Measurements

Setting a method to evaluate the mechanical properties of an aged asphalt mix using a rapid chemical measurement from small samples, would be of high interest at different steps of a road structure life cycle: at the design step, to optimise the estimates of the service lifetime usually based on the properties of unaged materials; during the service life, to update the residual lifetime expectation of an existing structure according to the actual properties of the in situ aged materials; and at the end of the service life or for maintenance management, to evaluate the recyclability of the materials of the structure. This study was carried out aiming at comparing results from Fourier Transform InfraRed and Dynamic Shear Rheometer tests. Experimental data came from an international round robin test, organised by the RILEM TC ATB, designed to set an ageing protocol on loose bituminous mixtures. The evolutions of the carbonyl index (ICO) calculated from the FTIR spectra are compared to the evolutions of the parameters of a modified Huet Rheological Model (1S2P1D) fitted on the experimental linear viscoelastic data measured on the recovered binder. A significant relationship is observed suggesting that chemical and rheological properties could be correlated. Based on this observation, a method is proposed for predicting the G* values of a binder aged at a given ΔICO level. Subsequently, this method could be used to predict the complex modulus E* of a given mix from the shear modulus G* of the binder using existing binder/mix transfer models.

A dissipated energy comparison to evaluate fatigue resistance using 2-point bending

Abstract: Fatigue is the main failure mode in pavement engineering. Typically, micro-cracks originate at the bottom of asphalt concrete layer due to horizontal tensile strains. Micro-cracks start to propagate towards the upper layers under repeated loading which can lead to pavement failure. Different methods are usually used to describe fatigue behavior in asphalt materials such as: phenomenological approach, fracture mechanics approach and dissipated energy approach. This paper presents a comparison of fatigue resistances calculated for different dissipated energy models using 2-point bending (2PB) at IFSTTAR in Nantes. 2PB tests have been undertaken under different loading and environmental conditions in order to evaluate the properties of the mixtures (stiffness, dissipated energy, fatigue life and healing effect).

Cracking in Asphalt Materials

This chapter provides a comprehensive review of both laboratory characterization and modelling of bulk material fracture in asphalt mixtures. For the purpose of organization, this chapter is divided into a section on laboratory tests and a section on models. The laboratory characterization section is further subdivided on the basis of predominant loading conditions (monotonic vs. cyclic). The section on constitutive models is subdivided into two sections, the first one containing fracture mechanics based models for crack initiation and propagation that do not include material degradation due to cyclic loading conditions. The second section discusses phenomenological models that have been developed for crack growth through the use of dissipated energy and damage accumulation concepts. These latter models have the capability to simulate degradation of material capacity upon exceeding a threshold number of loading cycles.

Effects of Ageing on Warm Mix Asphalts with High Rates of Reclaimed Asphalt Pavement

Within the framework of the European Project SUP&R ITN a Ph.D. thesis is carried out to study the durability of asphalt mixtures made with the combination of high rates of reclaimed asphalt pavement (RAP) and warm mix asphalt technologies. For this purpose the complex modulus and fatigue resistance of three different asphalt mixtures, including surfactant modified and foamed warm mix asphalts, combined with RAP has been studied. The extra value is given by the application of an ageing procedure based on the oxidation of compacted materials in laboratory. It follows the recommendations of the RILEM TC-ATB TG5, which distinguishes between short and long term ageing. Fourier Transform InfraRed (FTIR) tests were carried out on the extracted bitumens to quantify the oxidation levels. An increase of the norm and a decrease of the phase angle of \( \left| {{\text{E}}^{*} } \right| \) at 15 °C 10 Hz with ageing and RAP addition are experienced for all the mixtures. Similarly the slopes of the fatigue laws tend to increase with ageing. A consistent correlation is observed between these evolutions and the evolution of the carbonyl index. In general, the tendency is similar for all procedures, so the use of warm technologies combined with high RAP amounts may need to be considered.

Long term properties assessment of HMA and WMA with RAP through the apparent molecular weight distribution variation of the bitumen

The δ-method previously developed in IFSTTAR, is employed to determine the long term properties of asphalt mixes with reclaimed asphalt. This δ-method allows the calculation of apparent molecular weight distribution from rheological measurements. Its potential benefits as a tool for better understanding the key points of bituminous mixes recycling process is assessed. The study is carried out on twelve mixtures including two different types of warm mix asphalt techniques (surfactant and foamed bitumen) combined with the addition of high rates of reclaimed asphalt pavement. Samples are submitted to an oxidative aging process based on the protocol proposed by the RILEM Technical Committee-ATB TG5 consisting in two separate aging phases, a short term stage (corresponding to transport and spreading) and a long term aging equivalent to service life. The changes observed on the apparent molecular weight distribution with ageing and/or when reclaimed asphalt is added show that the δ-method could help to characterize structural ageing according to the different mixtures processes and its evolution. This may allow a better assessment for the long term performances of bituminous mixes depending on the manufacturing process.