EVALUATION OF CONVENTIONAL AND SUPERPAVE MIX DESIGN USING NEAT AND MODIFIED BINDER

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.