Abstract:
The primary objective of any asphalt mix design method is to establish an economically
efficient combination of bitumen and aggregates in an appropriate proportion such that it
yields a paving mix with sufficient amount of asphalt binder, desirable percentage of air
voids, VMA, VFA, suitable workability and satisfactory performance. Moreover, the
asphalt mix composition, i.e. proportion of asphalt cements (Optimum Asphalt Content),
aggregate and mineral filler has a substantial impact on its resistance against pavement
distresses. With the advancement in technology, the traditional Marshall mix design
method which was introduced in 1939 has become obsolete and outdated. The impact
compaction technique implemented in Marshall method is considered a poor reflection of
actual field compaction in view of the fact that pavements are subjected to gradually
applied compressive loads by compaction rollers and traffic. On the other hand,
Superpave mix design technique, which was established in 1993, is gaining attraction of
many state highway departments due to its better simulation of field compaction
characteristics and incorporation of environmental conditions, heavy traffic loading etc.
In general, asphalt concrete mix is designed in such a way that it possesses enough
stiffness to prevent major deformations without compromising its flexibility. Since the
Indirect Tensile Strength (ITS) and Resilient Modulus (MR) are reliable indicators of
asphaltic pavements’ stiffness, both these parameters (MR and ITS) are considered in this
research work to characterize the permanent deformation behavior of asphaltic mixtures.
This comparative study is aimed to analyze both design methods on the basis of
volumetric properties and performance evaluation by using the materials procured from
same source and adopting identical aggregates’ gradation complying with NHA
specifications which are most commonly used all across Pakistan for pavements design.
The results of performance testing were quite propitious and the implementation of
Superpave mix design approach is strongly recommended.
