Rehman, Amara (2020-07). Microstructure and Performance Analysis of Polyethylene-Modified Asphalt. Master's Thesis. Thesis uri icon


  • Asphalt is one of the most commonly used materials in the road construction industry. Asphalt binder is used to bind aggregate particles to form the asphalt mixture, which is the material used for the construction of pavement layers. The properties of asphalt binder influence the durability and strength of the mixture. Virgin asphalt does not have the properties to withstand the severe service conditions as it is prone to resistance distresses such as rutting and cracking. Rutting is a result of plastic deformation due to application of heavy loads at elevated temperatures. Low temperatures cause thermal cracking while repetitive loading causes fatigue cracking. All these factors contribute to adverse effects on pavement performance and road safety leading to premature failures and extensive maintenance. The addition of modifiers to asphalt is a common technique to enhance the mechanical properties of virgin asphalt and reduce maintenance cost. These modifiers aim to increase asphalt resistance to permanent deformation at high temperatures and/or increase its resistance to cracking at low and intermediate temperatures. This study analyzed the effect of adding two different grades of low-density polyethylene (LDPE) (LDPE4 and LDEP70) and polyethylene wax to asphalt binder as modifiers to enhance performance. LDPE 70 had a much higher melt flow index and lower molecular weight than LDPE4. The analysis focused on the microstructure and rheological properties. Various tests including optical imaging, dynamic and steady shear rheological measurements, thermogravimetric analysis, and differential scanning calorimetry were conducted. The results indicate that LDPE 70 showed lower crystallinity than LDPE4 and performed better in terms of dispersion and uniform particle size distribution along with better performance grade of the binders. On the other hand, although, PE wax reduced the phase separation in LDPE4 blends, it caused agglomeration in LDPE70 blends. It is suggested that further research be done going forth with LDPE70 and other compatibilizers such as to reduce phase separation as PE wax is not a suitable one.

publication date

  • July 2020