Development and Impact of the Egyptian Climatic Conditions on Flexible Pavement Performance

Abstract

Pavements are subject to environmental conditions, which affect the performance of both flexible and rigid pavements. The current flexible pavement design system in Egypt relies primarily on the 1993 American Association of State Highway and Transportation Officials (AASHTO) Design Guide. The method has many limitations. One of the serious limitations is the empirical drainage layer coefficients. These coefficients in addition to the seasonal variation of the roadbed resilient modulus are the only environmental consideration in the method. The newly AASHTO released production version of the Mechanistic-Empirical Pavement Design Guide (MEPDG) which is called AASHTOWare Pavement ME Design was developed to overcome the limitations inherent in the AASHTO 1993 method. Unlike the AASHTO 1993 method, Pavement ME Design method considers the variation in moisture and temperature on the mechanical properties of the pavement layers. Thus, the main objective of this study was to develop the climatic data to facilitate the implementation of Pavement ME Design in Egypt and study its influence on the pavement performance. Pavement ME required climatic data which are the hourly air temperature, precipitation, wind speed, sunshine and relative humidity were collected for 16 climatic locations distributed all over Egypt for four years. The quality of the data was checked and verified and the data was transformed to the format required by the software. A typical flexible pavement section was simulated using the ME design at the 16 different climatic locations and the performance predicted using the ME Design was analyzed. The performance indicators predicted by Pavement ME are rutting, alligator fatigue cracking, longitudinal cracking, thermal cracking, and International Roughness Index (IRI). Results showed that the pavement performance is significantly affected by the change in the climatic data. As expected, for Egypt, the most significant influence was on the predicted rutting of the Asphalt layer.