Abstract:
Traditionally Marshall Mix Design is used to find out volumetric properties and
optimum bitumen content but it does not represent the actual field conditions faced by
asphalt pavement. So a new method known as Superpave (Superior Performance
Asphalt Pavements) was introduced by Strategic Highway Research Program (SHRP)
established in 1987 in USA. The ideal condition will be if the samples prepared and
compacted in laboratory are close enough to represent field conditions.
There are several additives to improve the behavior of bitumen in severe climatic
conditions (especially in warm climate-70% of Pakistan Area) and under over loading
(common case in Pakistan) where use of neat bitumen (only bitumen) makes pavement
susceptible to pavement failures like rutting etc. Additive usage may have some
negative effects on bitumen properties with their positive effects so it is really important
to study the impact of modifier addition before using it. Our project aims to compare
the volumetric properties of Marshall Mix Design and Superpave Mix Design using
Neat Bitumen and Modified Bitumen (Bitumen and DuPont Elvaloy 4170) and compare
the impact of modification of bitumen on volumetric.
The materials used in our study are, aggregate procured from Margalla Hills Taxila,
bitumen of grade 60/70 from Attock Refinery Limited (ARL) and DuPont Elvaloy 4170
Reactive Ethylene Terpolymer (RET) as a modifier/additive. Performance testing of
aggregate and bitumen was conducted in the laboratory and test results were compared
to standard values. Bitumen was modified using modifier (1.5% DuPont Elvaloy 4170
Reactive Ethylene Terpolymer (RET)) according to standard procedure of mixing. The
bitumen contents used to prepare samples were 4%, 4.5%, 5% and 5.5%.For each
bitumen content 3 samples were prepared for Marshall Mix Design as well as
Superpave Mix Design using and modified binders, thus resulting in total of 48 samples.
After the preparation, samples were tested and volumetric properties were found out.
Optimum bitumen contents for Marshall Mix Design using Neat Bitumen, Marshall
Mix Design using Modified Bitumen, Superpave Mix Design using Neat Bitumen and
Superpave Mix Design using Modified Bitumen were found out and stated. At last
volumetric properties of above mentioned mix designs were compared and conclusion
were made.
