Anne Millien

Bio: Anne Millien is an academic researcher from University of Limoges. The author has contributed to research in topics: Asphalt concrete & Asphalt. The author has an hindex of 11, co-authored 25 publications receiving 401 citations.

Mechanical Testing of Interlayer Bonding in Asphalt Pavements

Abstract: Steadily increasing requirements on pavement performance properties, in terms of bearing capacity and durability, as well as new innovative developments regarding pavement materials and construction, are observed worldwide. In this context interlayer bonding at the interfaces of multi-layered bituminous systems is recognized as a key issue for the evaluation of the effects, in terms of stress-strain distribution, produced by traffic loads in road pavements. For this reason a correct assessment of interlayer bonding is of primary importance, and research efforts should be addressed in order to improve the lack of correlation and/or harmonization among test methods. Following this principle RILEM TG 4 organized an interlaboratory test in order to compare the different test procedures to assess the interlayer bonding properties of asphalt pavement. The results of the experimental research are presented with a preliminary overview of basic elements, test methods and experimental investigations on interlayer bonding. Then the RILEM TG 4 experimental activities, based on the construction of three real- scale pavement sections, are presented in detail. Each pavement section was composed of two layers, and three different interface conditions were chosen. The first pavement was laid without interface treatment and the others with two different types of emulsion. Fourteen laboratories from 11 countries participated in this study and carried out shear or torque tests on 1,400 cores. The maximum shear or torque load and the corresponding displacement were measured, and the shear or torque strength was calculated as a function of the following parameters: diameter, test temperature, test speed, stress applied normal to the interface and age of the specimen. The results of this study are presented in terms of precision and correlations regarding the parameters which results in useful information on asphalt pavement interlayer bond tests.

Shear Fatigue Behaviour of Tack Coats in Pavements

Abstract: For many years, pavement engineers use mechanistic design methods that are based on algorithms to compute stresses, strains and displacements in a flexible pavement structure, or in a multi-layered structure in general. Most of these methods assume, to ease the modelling of the structure and the computation process, that the layers are fully bonded or completely unbounded to each other. Moreover, determining the effectiveness of the bonding between two layers is difficult since there is no standard test procedure to assess it. Hence, proper modelling of the interface bonding condition will represent an important finding in understanding the real behaviour of road structures, and will lead to reduce maintenance and rehabilitation costs. Asphalt emulsion is commonly used, as tack coat, to ensure the bond between two pavement layers. This study deals with an experimental characterization of interfaces shear fatigue behaviour through laboratory tests. A testing device for determining the shear fatigu...

Digital image correlation techniques to investigate strain fields and cracking phenomena in asphalt materials

Abstract: This paper is the outcome of a specific task group of the RILEM Technical Committee 241-MCD “Mechanisms of Cracking and Debonding in Asphalt and Composite Pavements”. The group on “Advanced Measurement Techniques” was established in 2011 to investigate DIC applications for non-destructive and non-contact measurements of strain fields during laboratory testing. The paper illustrates different DIC/optical flow applications in measuring strain distribution during laboratory testing. Specific applications of DIC for evaluating crack initiation and crack propagation in asphalt materials are presented.

Nonlinearity, Heating, Fatigue and Thixotropy during Cyclic Loading of Asphalt Mixtures

Abstract: This paper describes investigation into the change in complex modulus (norm and phase angle) during cyclic tests on bituminous mixtures. The change can be explained by four phenomena: nonlinearity, heating, thixotropy and fatigue. An experimental campaign has been performed at ENTPE laboratory in order to identify and quantify the first three phenomena. The analysis of the results reveals that the two reversible effects (heating and thixotropy) are very important and can not be ignored when interpreting fatigue tests. Nonlinearity, for the rather small strain level amplitudes considered in our experimental campaign (up to 122 μm/m), is also shown to be reversible. Heating is due to the viscous dissipated energy that heats the specimen. At the beginning of the test, temperature increase in the sample is shown to be proportional with the total dissipated energy. Thixotropy effect is quantified. In addition, it is shown that thixotropy effect can be modeled using an equivalent temperature increase.

Testing Protocols to Ensure Performance of High Asphalt Binder Replacement Mixes Using RAP and RAS

Abstract: The use of reclaimed asphalt pavement (RAP) and recycled asphalt shingles (RAS) in asphalt concrete (AC) mixtures can reduce demand for virgin aggregates and asphalt binder, bringing environmental and economic benefits. However, replacing virgin asphalt binder in AC mixtures poses challenges in terms of mixture volumetrics and low-temperature cracking, fatigue cracking, and other deterioration related to cracking. To counter these effects, softer virgin asphalt binder grades or modifying agents are used to improve production consistency. The purpose of this study was to develop and evaluate protocols, procedures, and specifications for testing engineering properties and performance of AC mixtures with high amounts (up to 60%) of RAP and RAS. The criteria for selection of the test method were (1) statistically significant spread in test outcome, representing a mix’s cracking resistance; (2) applicability and seamless implementation; (3) correlation to other independent test methods and engineering intuition; and (4) correlation to field performance. A practical test method, the Illinois modified semi-circular bending test (IL-SCB) was developed that can be readily implemented to quantify AC mixture’s cracking potential. In addition, a flexibility index (FI) was introduced to determine cracking resistance in a consistent way. The IL-SCB showed consistent and repeatable trends for changes in AC mix design properties. The developed FI was shown to provide greater separation between AC mixes to capture some of the changes that could not be captured by fracture energy alone. This approach does not enforce any limits on any AC mixture design characteristics, such as RAP and RAS content, or other alternative materials or technologies. Instead, it categorizes AC mixes based on their performance index. Hence, this approach encourages innovation and sustainability at the same time.

The Grid Method for In‐plane Displacement and Strain Measurement: A Review and Analysis

Abstract: The grid method is a technique suitable for the measurement of in-plane displacement and strain components on specimens undergoing a small deformation. It relies on a regular marking of the surfaces under investigation. Various techniques are proposed in the literature to retrieve these sought quantities from images of regular markings, but recent advances show that techniques developed initially to process fringe patterns lead to the best results. The grid method features a good compromise between measurement resolution and spatial resolution, thus making it an efficient tool to characterise strain gradients. Another advantage of this technique is the ability to establish closed-form expressions between its main metrological characteristics, thus enabling to predict them within certain limits. In this context, the objective of this paper is to give the state of the art in the grid method, the information being currently spread out in the literature. We propose first to recall various techniques that were used in the past to process grid images, to focus progressively on the one that is the most used in recent examples: the windowed Fourier transform. From a practical point of view, surfaces under investigation must be marked with grids, so the techniques available to mark specimens with grids are presented. Then we gather the information available in the recent literature to synthesise the connection between three important characteristics of full-field measurement techniques: the spatial resolution, the measurement resolution and the measurement bias. Some practical information is then offered to help the readers who discover this technique to start using it. In particular, programmes used here to process the grid images are offered to the readers on a dedicated website. We finally present some recent examples available in the literature to highlight the effectiveness of the grid method for in-plane displacement and strain measurement in real situations.