About MCD2016 Conference:
The 8th Rilem International Conference on Mechanisms of Cracking and Debonding in Pavements (MCD2016) was held in Nantes (France) from June 7 to 9, 2016 (mcd2016.sciencesconf.org). More than 230 participants from 33 different countries have attended the conference hosted by the French Institute of Science and Technology for Transport, Development and Network (Ifsttar). This scientific event was coordinated with the activities of the Rilem Technical committee (TC) N°241, that aimed at developing a deeper fundamental understanding of the Mechanisms responsible for Cracking and Debonding (MCD) in asphalt concrete and composite (e.g., asphalt overlays placed on PCC or thin cement concrete overlay placed on asphalt layer) pavement systems. Over a 5-year time period from 2011 to 2016, the activities of the TC241-MCD have been led by William Buttlar (University of Missouri, USA), and Armelle Chabot (Ifsttar, France). This Rilem TC was organized within three task groups (TG): TG1 - Cracking in Asphalt Material; TG2 - Interface Debonding Behavior, and; TG3 - Advanced Measurement Systems for Crack Characterization led by Eshan V. Dave (University of New-Hampshire, USA), Christophe Petit (l’Université de Limoges, France) and Gabriele Tebaldi (University of Parma, Italy and University of Florida, USA) respectively. The purpose of the 8th Rilem international conference was to present the results of TC 241-MCD as well as the latest advances in research to analyse mechanical damage and its detection in multilayer systems. It has aimed to better detect the initiation and the propagation of cracks in pavement and also to have tools that make it possible to find technical solutions for prevention (or to limit) cracking in current and emerging infrastructure. MCD2016 has favoured interactions between different research communities to help apply these advances to pavement structures continually during the three events. In each one of those thematic days, two plenary lectures started the day. For each day, one plenary lecturer was chosen to be experts in the field of damage and cracking, and one as an expert in pavement engineering. During the presentation of the 106 accepted papers (half in podium sessions and half in poster sessions), 75% authors came from outside France. Conference also included four workshops. Throughout the event, participants had the opportunity to share their knowledge.
Best paper selection process:
Of all the MCD2016 papers published in Rilem Book series volume 3 2016 (Springer - doi: 10.1007/978-94-024-0867-6), invitations were sent for a few selected authors to submit an extended version of their MCD2016 work. This selection process was based on both the quality of the 6-page short paper reviewed by two scientists on the MCD2016 Scientific Committee and the quality of the presentation as evaluated by the designated session chair. Moreover, publications were accepted in Spring 2017 in thematic issues of the three following journals: Road Materials and Pavement Design (RMPD), European Journal of Environmental and Civil Engineering (EJECE), and ASTM Journal of Testing and Evaluation (JTE).
Present thematic issue content:
This international journal, European Journal of Environmental and Civil Engineering (EJECE), published a thematic issue entitled “Debonding Mechanisms in Various Interfaces between Layers”, related to the MCD2016 topic: “Debonding mechanisms between layers of asphalt and composite pavement”. From the 36 MCD2016 papers submitted on this topic, the five papers selected, revised and accepted for this thematic issue had all followed the standard EJECE review process. They present the main advances achieved in understanding pavement interface behaviour.
One of these papers focuses on knowledge acquired relative to a “field” study; it seeks to evaluate the influence of various tack coat application parameters in obtaining strong adhesion between layers. Using core specimens stemming from four different test sections, this paper provides the critical aspects of interface behaviour through standard testing.
Another paper presents reinforcement pavement analyses; it illustrates that the use of grids to reinforce pavements may result in improved pavement strength, yet on the downside this practice may adversely affect the bond between the grid and the layers, hence reducing pavement performance. The competition between these two effects is discussed, along with the potential disturbance to interlocking between layers due to the presence of a grid. The benefits of a tack coat are also exposed.
In support of the notion that interlocking due to surface roughness is a key parameter in interface behaviour, in addition to a tack coat potentially enhancing the bond between layers, the third paper offers a new interface model. The parametric numerical analysis reveals that the influence of the interface roughness parameter introduced into the model may explain the results derived during experimental studies on the interface shear mode. A macro-scale interface damage model, which includes roughness as an internal variable, is also proposed for pavement structures with smooth interfaces.
The final two papers demonstrate that the presence of water affects interface bond sustainability in a composite pavement and needs to be quantified. Papers 4 and 5 show that even if an old asphalt pavement is rehabilitated and heavily reinforced by means of a cement concrete overlay, moisture still undermines the strong bond between layers. Modelling and experimental results clearly indicate a softened interface under wet conditions in comparison with dry conditions. Digital Image correlation techniques improve the understanding of investigation mechanisms produced in the lab for some of these tests.
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Christophe Petit
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