Abstract: The aim of this paper is to present a specific four-point bending test with a specific model to help investigate the crack initiation and propagation at the interface between layers of composite pavements The influence of the geometry on the delamination phenomenon in specimens is analyzed Considering the deflection behavior of specimens, both experimental and analytical results are compared Two different types of interface (concrete / asphalt and asphalt / concrete) are tested in static conditions Different failure mechanisms whose mainly delamination is observed The crack mouth opening displacement is monitoring by means of linear variable differential transducer (LVDT) The strain energy release rate is provided and compared successfully to the literature
Abstract: In order to investigate interlayer debonding near skrinkage cracks or joints of “composite” pavements, a four-point bending test on bi-layer structures is performed. Before mixed mode failure, the quasi-analytical calculations obtained by a specific elastic model match experimental results under static and controlled displacement conditions. Both the interface normal and shear stress intensities determined at the specimen edge lie within the range of values found in the literature for cement concrete overlays on a bituminous material type of interface. The strain energy release rate is calculated. Results are discussed relative to both data provided in the literature and testing campaigns.
Abstract: The degradation of the bituminous pavement structures is due to the several external loads (climatic conditions and traffic) and the weak bond between layers. Thus, it is important to take into account the interface behavior in the pavement computational design which is never considered actually. In order to provide reliability and efficiency of the design methods, the interface characterization study is required. In this study, a monotonic tensile test was performed for better understanding of the global and local structure behavior by using the Digital Images Correlation (DIC) analysis. The obtained results allow us to characterize the constitutive law of interface and mechanical parameters such as: stiffness, damage evolution, and release rate energy.
Abstract: Considering that water may cause a separation of interfaces between layers of pavement structures, specific test on bi-layer specimens is performed in a water bath. For the study of the bond between layers made of cement concrete overlay on bituminous material, four-point bending results show a competition between different failure mechanisms. Actually a very good bond resistance between layers compared to the fracture tension resistance of the cement concrete layer is preliminary observed in dry conditions. In this work, first results of the water effect on the behaviour of such a material interface are presented. The final fracture length of the specimen and the corresponding curve of force-displacement highlight the influence of water immersion on the debonding failure mode. The field displacement measurement obtained by Digital Image Correlation is used to improve the understanding of the fracture scenario.
Abstract: A bonded concrete overlay consists of a concrete layer poured over a deteriorated pavement. Its mechanical performance depends on the quality of the bond between the lower and the uppermost layers. This paper reports an extensive experimental program to evaluate bond strength between Conventional Concrete (CC) and Asphalt Concrete (AC) substrates and Self-Compacting High-Performance Concrete (SCHPC) overlays. In all, 8 interface treatments are tested under Direct Tension, pure shear “LCB”, and compressive Slant Shear tests. The results show that direct pouring of the SCHPC overlay over CC and AC substrates produces similar or higher strengths than the other treatments analyzed.
Abstract: The performance and durability of multi-layered pavements strongly depend on interlayer bonding between layers, especially for pavements with a thin or ultra-thin surface course. These pavements, comprised of several differing material layers, are often subjected to premature distresses (corrugation, peeling, slippage or fatigue cracking, etc.) caused by poor interface bonding. This chapter summarizes the different bond characterization tests available around the world (mostly in the laboratory) available to characterize the bond between pavement layers. Many of the tests can be performed on specimens prepared in the laboratory or on cores or slabs obtained from the pavement. Mostly, “pure” fracture mode test methods (opening mode I or in-plane, shear mode II or out-of-plane, shear mode III) are currently used worldwide for determining the interlayer bond of pavement layers. Most of the mixed-mode test methods (mainly for the combination of Modes I and II) were developed by a few research teams and there are therefore no standard tests. Although tack coat type and content are the main parameters studied by researchers and engineers, surface roughness, moisture, freezing, and presence of dust or debris on the interface are additional parameters that may decrease bonding performance.
Abstract: To approach the three-dimensional stress state in multi-layered composites, a laminate theory which considers a kinematic field per layer (particle) is used. Thus, interlaminar stresses are naturally introduced to carry out the equilibrium conditions of the plies. These stresses have a physical meaning and represent the exact out-of-plane 3D stresses calculated at the interface between two layers. These simplified models are able to provide finite interfacial stresses, even at the free edge of a structure. The first part of the paper describes the model and shows its validation by means of a comparison with finite element calculations. The model can involve inelastic strain fields in the layers and fields of displacement discontinuities at the interfaces. These inelastic fields, such as interface sliding, are assumed to be known by the user. The second part proposes some relevant criteria able to predict delamination initiation in some angle-ply laminates based on the model results. The laminates considered here are elementary cross-plies ±(θ n ) s with 0 < 30° to avoid more complicated phenomena as fiber rotation, transverse cracking or other non-linearity. The three criteria proposed herein integrate naturally interface stresses, and have been confronted to experimental results in mode III, for a ±(θ n ) s . The first criterion is based on the calculation of the maximum interfacial shear stresses. The second criterion is based on the analytical calculation of the strain energy release rates in a delaminated multi-layer. The third criterion is based on an experimental observation: a critical interface sliding value seems to govern delamination onset during tensile tests. Two plastic models were proposed for relating the interface sliding with the interfacial stresses: perfect plasticity and plasticity with a linear softening. Brittle linear elastic (criteria 1 and 2) and plastic analyses both provide accurate predictions. A more detailed study of this presumptive contradictory assertion is lastly led.
Abstract: La these a pour but de concevoir un outil simple d'utilisation, pour l'ingenieur, capable d'analyser les champs de contraintes tridimensionnels responsables de delaminage au bord ou de fissuration transverse dans les materiaux multicouches. Dans la premiere partie du memoire, nous construisons des modelisations multiparticulaires (M4) a partir de champs de contraintes tridimensionnels approches ecrits sous forme de polynomes de Legendre en z par couche. Les coefficients de ces polynomes sont des champs en (x,y) relies aux efforts generalises. Nous utilisons la formulation d'Hellinger-Reissner pour en deduire les deplacements et les deformations generalisees associees. Par stationnarite de la fonctionnelle, nous donnons les equations d'equilibre, les conditions aux limites et le comportement ecrit en souplesse. La richesse plus ou moins grande des champs de contraintes approches ainsi construit mene a 7n, 5n, 3n et (2n+1) (n: nombre de couches) equations d'equilibre dans le plan. Dans la seconde partie de la these, nous testons quatre modeles sur le probleme de la traction simple pour des stratifies non troues d'empilement quelconque et troues d'empilement (0°, 90°)s. Nous posons analytiquement les systemes d'equations qui par combinaison se condensent en un systeme d'equations differentielles de degre 2 en y et dont la resolution se fait par le logiciel de calcul formel MATHEMATICA. Sur le cas du stratifie (0°, 90°)s non troue, nous montrons que l'energie due aux efforts manquants dans les modeles reduits ne disparait pas completement mais est transferee sur celles des efforts restants. Dans le cas du modele multiparticulaire M4_(2n+1)M (M: pour membrane) le plus simple, pour assurer l'equilibre global de la plaque, nous proposons un concept, generalisable, d'effort lineique de type Dirac dont l'intensite est relie au maximum des cisaillements au bord. Nous pensons que l'intensite du Dirac peut servir de base a un critere sur le delaminage.
Abstract: The debonding of FRP plates from concrete beams is not amenable to finite-element analysis; fracture mechanics, based on a global energy balance, offers a better alternative. An analytical model with energy calculations based on a revised version of Branson’s model (to take account of the reaction to the force in the FRP) has already been developed. This paper presents comparisons with a variety of experiments reported in the literature and shows that the model can correctly determine both the failure load and the failure mechanism. The paper shows that debonding often propagates in the concrete, just above the interface, and hence the failure load is dependent on the Mode I fracture energy of concrete. The method can also be used to determine when premature adhesive failure occurred prior to debonding within the concrete substrate.
Abstract: Ce travail a pour but d’etudier la durabilite mecanique du collage blanc (beton) sur noir (enrobe) sans
lequel deux structures de chaussee innovantes – le beton de ciment mince colle (BCMC) et le beton arme continu
sur grave bitume (BAC sur GB) –, constituees d’une couche de blanc mise en oeuvre sur une couche de noir,
n’ont aucun interet. Tout d’abord, on s’attache a identifier, a partir d’une analyse bibliographique, un mode de
ruine du collage sous l’action du trafic. On etablit que les fissures de retrait de la couche de beton constituent le
point a partir duquel s’initie et se propage le delaminage. Dans un second temps, ce mode de ruine est simule par
un essai mecanique de fatigue en laboratoire, qui permet d’observer un delaminage progressif. Dans cet essai, le
grenaillage de l’interface, compare au non grenaillage, apporte un collage plus durable. Une analyse mecanique de
l’essai est proposee et necessite d’etre validee avec plus d’essais dans l’avenir. Ensuite, on met au point d'une
methodologie de suivi « in situ » de la qualite du collage par CND, basee sur l’utilisation d’un systeme
d’auscultation mecanique dynamique. Finalement, l’analyse des essais echelle 1:1 montre deux evolutions du
collage. Pour la RN4, chaussee epaisse presentant un engrenement mecanique au niveau des fissures, on ne note
aucune evolution du decollement initial apres 2 ans. Pour la maquette de structure reelle, a couches amincies et ne
presentant pas d’engrenement mecanique dans les fissures, on observe, apres 1 million de cycles de sollicitation
des simulateurs de trafic accelere FABAC, le mode de ruine attendu soit un delaminage s’initiant au niveau des
fissures de retrait.