Theoretical Review of Different Asphalt Mix-Design Methods and their Applicability for Developing Countries like Zambia

Asphalt pavements in Zambia have been experiencing premature failures due to distresses such as rutting, fatigue cracking, bleeding, moisture damage, and pot-holing. Most of these failures have been accusingly attributed to poor workmanship of Contractors who fail to adhere to specifications. Literature has, however, revealed that the materials used and the mix-design methods adapted also have a significant effect on the long-term performance of these asphalt pavements. To mitigate for these effects, some developed countries have developed new approaches like Superpave and Balanced Mix Design (BMD) methods that are performance-based, for the design of Hot Mix Asphalt (HMA) with the primary objective of improving the performance of asphalt pavements. By contrast, Zambia, like most developing countries, still uses the empirical Marshall Stability method that has inherent challenges in satisfactorily addressing the above mentioned pavement failures. This paper presents a theoretical review of the material types and mix-design methods currently used in Zambia to verify if premature failures of pavements can be attributed to the materials used and/or the mix-design methods adapted. Different mix-design methods and their characteristic attributes were comparatively reviewed to assess their potential applicability for use in a developing tropical country like Zambia.