Jean-Pascal Bilodeau

Gradation influence on frost susceptibility of base granular materials

Base granular materials are generally considered non-frost susceptible, which is an adequate assumption based on widely recognised frost criterions. However, their frost susceptibility is influenced by the presence of water that can unavoidably penetrate pavement structures. Even if unsaturated, freezing of unbound granular materials causes a net volume gain and an increase in water content which affect pavement performance during the spring period. This paper presents the results of a laboratory investigation on the effect of gradation on frost susceptibility, quantified with the segregation potential (SP), of three aggregate sources. The results suggest that SP values for all sources are strongly related to a fine particles state parameter. Moreover, the source influence was found to be described adequately with a parameter describing fine particles grain size distribution uniformity and fines specific surface. A model is proposed which combines gradation and mineralogical source effects on frost susceptibility of base granular materials.

Use of falling weight deflectometer time history data for the analysis of seasonal variation in pavement response

This paper presents the results of an exploratory analysis of falling weight deflectometer (FWD) data collected on a large project about the spring thaw behaviour of pavements. The test site includes four test sections, two of which are conventional flexible pavement structures, whereas the other two are built with a cement-treated base. The aim of this study is to verify the applicability of using FWD time history data to evaluate damage to a road during the thawing period. The applicability of the analysis techniques is verified through the phase angle and dissipated energy. The data analyzed were obtained from tests conducted with an FWD on one flexible pavement test section. The results obtained showed a clear difference between the winter, thawing, and summer periods. It was found that the phase angle and dissipated energy can be used to evaluate the road damage during the thawing period through quantification of the phase angle and dissipated energy. These factors can also be used to describe the pa...

Erosion susceptibility of granular pavement materials

Turbulent flows, such as wind and runoff water, affect the integrity of base granular materials in paved roads shoulders and unpaved roads. This paper presents the results of a laboratory investigation on the effect of base granular gradations on their erosion resistance under turbulent flows. The tests were performed with the turbulent flow test designed to be used with conventional geotechnical laboratories equipment. Several gradations curves, within and outside the Quebec Ministry of Transportation grading envelope, were tested in order to examine the influence of the variation of base granular materials gradation characteristics on the erosion susceptibility. For unbound materials, it was found that properties related to material voids and the permeability of the material (uniformity coefficient, fine fraction porosity and estimated permeability) and property related to the fine particles content are strongly related to the erosion rates (ER) measured with the turbulent flow test. It was demonstrated that the performance of base granular materials under turbulent flows can be controlled using these specific parameters.

Wide-Base Single-Tire and Dual-Tire Assemblies: Comparison Based on Experimental Pavement Response and Predicted Damage

Past studies suggest that wide-base single tires [WBSTs (455/55R22.5)] induce pavement strains that can be either more or less severe than those caused by dual tires of similar sizing, as strain depends on both the spatial direction of the strain and where the strain is located in the pavement. An experimental assessment of strain basins occurring at various positions within the hot-mix asphalt (HMA) layer, as well as within pavement unbound layers, was undertaken to further this understanding. The method and the results of this assessment, along with the pavement damage predicted by using available models are presented. Four failure mechanisms were considered: HMA rutting, both bottom-up and top-down fatigue cracking, and structural rutting. Testing was conducted at two sites on four roads over a range of loads, pressures, and temperatures by using WBSTs and different sizes of dual tires. Data analysis showed several critical strain zones near the tire edges and at the tire center. Optic-fiber sensors were used to analyze these phenomena. HMA rutting was calculated by considering vertical shear strain near the surface under the edge of the tires. Other failure mechanisms were calculated by using maximum strain. The results predicted that the WBSTs tested may induce less damage in the upper part of the HMA layer and more damage when fatigue cracking and rutting of soils and unbound materials are considered. Data collected were from specific tires, and all tests were conducted only under smooth, steady-state rolling conditions. Thus, results should neither be generalized to all tires nor extrapolated to the prediction of actual field performance.

Stress distribution experienced under a portable light-weight deflectometer loading plate

In the field of pavement engineering, the need to rapidly and economically obtain properties of soils and materials has given rise to the development of many non-destructive techniques. Portable light-weight deflectometers (PLWD) are relatively new deflection-based tools. As a consequence, the main factors influencing the quality of the results obtained using such a tool are still being investigated. Therefore, through finite element modelling and experimental measurements, this research focussed on the stress distribution and stress variability under a PLWD loading plate and how it is influenced by stress level, plate diameter, rubber mat use and rubber hardness. It was shown that the stress distribution factor used for the calculation of elastic modulus from deflection testing is significantly influenced by the loading plate diameter. Moreover, the use of a harder rubber mat was found to be better, but no significant effect was observed for bonded rubber mat conditions.

Development of models for the interpretation of the dynamic cone penetrometer data

This study deals essentially with the development of models that describe the relations between the strength properties of soils (undrained shear strength obtained with a vane tester) on one hand, and the resilient properties (back-calculated modulus obtained with deflection tests) on the other hand, and the penetration index values obtained with the dynamic cone penetrometer. Laboratory tests were performed on five coarse-grained reconstituted soils. Also, field tests were performed on 10 fine-grained soils and on each of the four subgrade soils of the Laval University Experimental Test Road Site. The results obtained in the laboratory and in the field were compared and analysed in order to develop the relations between the strength and the resilience for different types of soils. Using a statistical analysis with three different sophistication levels, reliable correlations that include explanatory variables were developed.

Optimisation de la granulométrie des matériaux granulaires de fondation des chaussées

Les materiaux granulaires de fondations de chaussees jouent un role structural important mais sont aussi affectes par l’environnement. La granulometrie et la source de granulats vont changer la facon dont ces materiaux reagissent a ces sollicitations. Cette etude cherche donc a evaluer la performance globale des materiaux granulaires face aux contraintes mecanique et environnementale. Le module reversible, la deformation permanente, la gelivite et la conductivite hydraulique ont ete mesures pour six granulometries et trois sources. Les resultats montrent l’effet significatif de la granulometrie et de la source dans le contexte d’un fuseau granulaire et permettent de suggerer des fenetres de performance granulometrique adaptees a des contextes de performance typiques. Ces effets de la granulometrie et de la source peuvent atteindre des facteurs 14 et 7 d’un point de sensibilite aux contraintes environnementales et des facteurs 3 et 2,5 d’un point de vue de la sensibilite aux contraintes mecaniques.

Albedo of Pavement Surfacing Materials: In Situ Measurements

In order to limit heat intake in the ground underneath pavements, high albedo surfaces can be used in cold regions to mitigate permafrost degradation. In this study, experimental sections at Site Experimental Routier de l’Universite Laval (Quebec, 2014), on the Alaska Highway (Beaver Creek, Yukon, 2012 and 2014 and at km post 1786, Yukon, 2014), and in Tasiujaq (Nunavik, Quebec, 2015) were used to document the effectiveness and durability of high albedo surfacing materials. The test sections were equipped with thermistors and data loggers recording surface temperatures. Albedo and skid resistance were also monitored at these sections. In addition to the experimental sites, several albedo measurements were made on asphalt surfaces to develop a relationship between albedo and pavement age.

Monitoring and Modeling the Variations of Structural Behavior of a Flexible Pavement Structure during Freezing

AbstractThis paper presents the results of a study carried out to monitor the structural behavior of a flexible pavement in cold regions, which is significantly affected by environmental factors an...

Monitoring of Flexible Pavement Structures during Freezing and Thawing

The structural behavior of flexible pavement in cold regions is greatly affected by environmental factors and traffic loads. The main objective of this study was to better understand the response of pavement structures during thawing and to better predict the loss and recovery of the bearing capacity as a function of the evolution of the thaw and temperature in the pavement. Two identical test sections were used; one was built in the geotechnical laboratory of Laval University and one was located at the Laval University Road Experimental Site (SERUL). Each layer of the tested sections was instrumented with strain, stress, moisture, and temperature sensors. In the laboratory, a heavy vehicle and environmental simulator, which can control the air temperature on the pavement surface, was used to apply real traffic loads and control temperature. A temperature of - 10°C was used for freezing, and a temperature of 10°C was used for thawing. The carriage speed was set a 5 km/h, the tire pressure was set at 700 kPa, and loads of 5000, 5500, and 4000 kg were tested to simulate standard, winter premium, and spring load restriction conditions. At the SERUL, a falling weight deflectometer (FWD) was used to simulate heavy loads. The results indicate that the freezing of a given structural layer reduces the strains and stresses in the layer, as well as in the underlying layers. After one freeze-thaw cycle, the reduced moduli in unbound materials indicate that some damage occurs during freezing and thawing. Also, strain increases significantly when the thaw front penetrates into the pavement and at the beginning of summer when the rise of temperature reduces the stiffness of the asphalt concrete layer. Finally, we noticed that, during freezing, a 10% load increase induces a 10% increase of strain and stress in the pavement structure.