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Monitoring the temperature gradient of pavement structure layers and its effect on the structural behaviour helped to establish a fundamental understanding of the magnitude and impact of these variations on the pavement response to different loading conditions. The performance of pavements clearly reveals the need to properly measure the distribution of stresses and strains within road layers over a period of time taking into account the effect of extreme temperatures. The adverse effects of traffic speed during hot weather conditions on the structural behaviour of the flexible pavement are briefly discussed and possible recommendations to overcome these effects. Structural data including stresses and strains were collected under the action of external loads applied by a calibrated test trucks. To mimic the effect temperature extreme events on the flexible pavements, the study was carried out on flexible roads immediately after the construction at 51o C (truck impact test) and 44o C (truck creep test) and after one year at normal operating temperature (20o C). The field results showed unprecedented high stress and strain levels caused by low asphalt stiffness when the asphalt mat temperature is above a normal operating temperature. Traffic-induced stresses and strains transmitted through the asphalt concrete layer to unbound materials of the asphalt concrete are directly influenced by the stiffness. The impact test using a truck speed lower than 25 km/h resulted in a very high truck pressure impact. This study confirmed that most of pavement performance problems occurred at locations were buses frequently stopped and areas close to traffic signals. This finding highlighted the importance of traffic speed impact, extreme hot weather events and the interaction of both., 2017 TAC Conference & Exhibition, September 24-27, 2017, St. John’s, Newfoundland, Canada

Over the past 120 years, the asphalt industry has evolved to become a multi billiondolar business achieving significant technological advances and providing better and effective road infrastructure. However, it has also been experiencing a number of problems. One such major problem is a perception, and arguably a reality, that asphalt pavements are not being designed and constructed to meet its long term objective or being cost effective. At the same time, there is a growing backlog of needs due to unexpected early asphalt road deterioration. This deterioration includes several problems such as early cracking, rutting, moisture damage and surface roughness. The result is that at the turn of the century, despite major efforts, better economic and technical solutions for these problems, more work remains to be achieved. On a positive note, however, the pressure to address these problems and develop better solutions has led to a number of key initiatives which are shaping the asphalt industry today. These initiatives include the Strategic Highway Research Program (SHRP), which deals in part with the characterization of asphalt materials and their performance under a wide range of in-service conditions. Also the use of advanced materials such as non-metallic polymeric grid and/or polymer modified asphalt binders to reinforce asphalt layers and/or improve their tensile and shear strengths and the introduction by many agencies of end-result specifications; some agencies are even going to long-term performance based specifications have contributed to an improvement in the pavement performance. There is no doubt that most of these developments, if not all have significant technical and economic potential. One of the unresolved problems is clearly appearance of surface cracks at early stage after construction of new asphalt layers. This paper reviews the state-of-the-art of the problem of surface cracking of asphalt pavements, it assesses theoretical and imperial models and approaches describing the causes and remedies of the cracking problem and provides an in depth analysis to the main causes and mechanisms that induce such cracking. Finally, the paper discusses better ways to minimize and hopefully eliminate the causes of the occurrence of early surface cracks of asphalt pavements.

Canadian Society for Civil Engineering 1998 CSCE Annual Conference: 10 June 1998, Halifax, Nova Scotia

Roadware 97 4th International Road Conference: 10 June 1997, Prague, Czech Republic

Canadian Technical Asphalt Association: 18 November 1996, Edmonton, Alberta

1995 CSCE Annual Conference: 01 June 1995, Ottawa, Ontario, Canada

Dynamic Interaction of Vehicles and the Infrastructure - Proceedings of DIVINE Special Session, 17th ARRB Conference: 1994

This paper introduces a simple mechanistic approach that describes the response of the asphalt-aggregate system to temperature changes. The concept recognizes the thermal incompatibility between asphalt cement and aggregate. Owing to the considerable difference in the coefficients of thermal expansion of aggregate and asphalt, the asphalt matrix will attempt to contract more than the aggregate during thermal cooling. An analytical model was derived to estimate the thermally induced stresses resulting from differential thermal contraction. The experimental investigation which is part of a study investigating adhesion, verified the findings of the analytical approach. Findings from this study explained field and laboratory observations made earlier by other investigators. These observations were associated with asphalt concrete low-temperature performance and its resistance to stripping.

72nd Annual Meeting, Transportation Research Board: 10 January 1993, Washington, D.C., USA

Canadian Technical Asphalt Association (CTAA): 1992, Victoria, British Columbia

Dabbour, E., Easa, S. M., Hassan, Y., & HaIim, A. E. (1996). Analytical model for intersection sight distance on 3-d highway alignments., Intersection sight distance is the adequate sight distance to be provided at two-way stop controIIed intersection. Current AASHTO poIicy provides an equation and charts for the required at-grade intersection sight distance so that a driver on the minor road can depart (crossing, turning Ieft, or turning right) safeIy, even though an approaching vehicIe on the major road comes into view as the stopped vehicIe begins to depart. The AASHTO modeI is based on two assumptions: (a) both minor and major roads are assumed to be straight without any verticaI or horizontaI curvature and (b) the intersection angIe is assumed to be 90. In many practicaI situations, however, we have to check sight distance for an existing three-dimensionaI (3D) highway aIignment where verticaI and horizontaI curves overIap at the intersection. This paper provides a new anaIyticaI modeI for intersection sight distance on 3D highway aIignments, which aIIows the major road to have verticaI and horizontaI curves with any intersection angIe. PracticaI graphicaI aids are deveIoped to determine the avaiIabIe intersection sight distance for different geometric aIignment variabIes (e.g., radius of horizontaI curve, Iane width, number of Ianes, Iength and grades of verticaI curve). The methodoIogy is iIIustrated using severaI numericaI exampIes