The Hot Mix Asphalt (HMA) industry in developing countries (in general) and in Pakistan (in Particular) is facing a substantial challenge to meet the increasing transportation demands in terms of traffic volume and loads. High ambient temperatures and truck loads further complicate the problem and accelerate premature pavement failure in Pakistan. This in turn taxes the limited resources and places undue burden on the socio-economic development of the country. In order to meet the challenge, the HMA industry and the transportation authorities must embark on critical endeavors to enhance the design of HMA and to improve the selection of the materials used in highway construction. These require better understanding of the impact of design methodologies and material characteristics on the long-term pavement performance. Improved pavement performance would significantly reduce both the required fund to maintain the highway network and the vehicle operating costs. Most pavement experts agree that good pavement performance cannot be attained unless the quality of HMA mixtures (the most important layer in a pavement system) is enhanced. Given the new technologies and advances in material types (such as modifiers), characterization techniques, and design methodologies, it is possible to design and construct high performance and durable pavements in a cost-effective manner.
The above scenario implies that a fundamental system design process must be established based on accurate, scientific and mechanistic methodologies. This in contrast with the present-day empirical design procedures based upon prior experience. Empirical procedures are not capable of analyzing the behavior of new materials, the impact of innovative construction techniques, and/or the effectiveness of new specifications.
Although, the majority of the primary road network in Pakistan is surfaced using HMA, none of the mixes have been properly characterized as to assess its long-term performance under the heavy Vehicular loads. HMA mixes consist of asphalt binder and coarse and fine aggregates. Hence, the Properties f each constituent material impact the overall performance of the HMA mix. To assure good and cost-effective pavement performance, the properties of each constituent material as well as those of the HMA mixes must be obtained. The objectives of the material testing program proposed herein are a) evaluate the physical, engineering and rheological properties of the various constituent materials of the HMA mixes and b) analyze the impacts of these properties on the long-term pavement performance in lieu of the local traffic and environmental conditions in Pakistan. Said program would ultimately lead to the implementation of Superpave mix design methodology (which was developed in the US through extensive research based on mechanistic principles) and the elimination of the outdated and empirical MARSHALL Mix design.
In summary, the goal of this study would assist the highway authorities and industries and to trail their staff in Pakistan to implement advanced testing techniques for the characterization of HMA mixes as to optimize pavement performance in a cost-effective manner. This goal is parallel to that of the USAID science and technology cooperative program. Achieving the goal would positively impact the socioeconomic environment in Pakistan.