Hamad I. Al-Abdul Wahhab

Department of Civil Engineering, King Fahd University of Petroleum & Minerals, Dhahran 31261, Saudi Arabia

Third Gulf Conference on Roads (TGCR06), March 6-8, 2006

Abstract:

The Arabian Gulf countries (GC) have invested more than US $32 billion in road construction over the last 20 years. The GC has undergone an extremely rapid rate of development in many directions. The construction of thousands of kilometers of freeways, expressways, and low-volume roads has played an important role in such development. Growth in socioeconomic and industrial sectors has been encouraged, resulting in the generation of a great deal of heavy vehicle transportation in cities and between cities. These rapid development rates have generated extremely large traffic volumes, especially those of heavy trucks, on the roadway network. The roadway capacity can properly accommodate these volumes. However, noticeable rutting problems have appeared during the last 10 years.

In Saudi Arabia, the Ministry of Transport, in an effort to solve the problem, has initiated a national study and started to replace affected pavements. The aims of this study were to identify possible factors which may relate to rutting and to recommend maintenance and repair criteria for existing rutted pavements. The study covered nineteen sections of eleven major highways. Results indicate a direct relationship between rutting and the percentage of air voids; the percentage of voids in mineral aggregate; the percentage of voids filled with asphalt, resilient modulus at 25^oC; and bitumen viscosity. These properties were used as bases for maintenance criteria as well as criteria for the design of mixes to better resist rutting. The study has also indicated that the problem has been aggravated by the high ambient temperatures and the inability of used binder specifications and mix design procedure to accommodate field conditions.

The current binder specifications, as applied in the Gulf countries including Saudi Arabia, Kuwait, Bahrain, Qatar, United Arab Emirates and Oman, are based primarily on either penetration or viscosity testing which does not properly account for pavement performance. Research was undertaken to provide a performance-based binder specification for the Gulf countries, based on the findings of the Strategic Highway Research Program (SHRP) carried out in the United States, considering the prevailing environmental and traffic conditions and type of locally produced bitumen. Results indicated that locally produced 60/70 penetration grade bitumen satisfies the environmental condition of less than 30% of the Gulf countries’ area. Air blowing of bitumen is required to satisfy the performance requirement of another 25% of Gulf countries’ area, while polymer modification is necessary to satisfy the performance requirements for the other parts of the Gulf countries which include eastern parts of Saudi Arabia, Kuwait, Bahrain, Qatar, United Arab Emirates and Oman.

Key words: Polymers, Air Blowing, Bitumen, PG Specifications, GC, SHRP