i8 | paving the way Paving the way: Bidbid-Sur Highway’s state-of-the-art techniques By Amal Hajj Ali and Roland Owaida, Dar Al-Handasah The Bidbid-Sur Highway project saw Dar’s Geotechnical & Heavy Civil Engineering Department implement highly effective road-paving techniques. An important part of Dar Al-Handasah’s work on the Bidbid-Sur dualization project, documented in this issue and the previous DarMagazine, involved pavement design and supervision of the execution. A team of Dar’s pavement design specialists from the Geotechnical & Heavy Civil Engineering (GHCE) Department drew up an appropriate approach for the new highway, and chose the pavement and materials most suitable for the project’s particular loading and climatic conditions. Specifications Two priorities for the Bidbid-Sur project were durability and high performance, and to ensure they were met, the team studied specialized industry standards: SP-1 Superpave Performance Graded (PG) Asphalt Binder Specifications and Testing, and AASHTO M320 Standard Specification for PG Asphalt Binder. Superpave technology had already been established in the United States and Europe for some time now. However, the technology started to spread in the Gulf region only recently. Dar decided to use PG asphalt in the Bidbid-Sur Highway project in Oman, a decision that was fostered by Oman’s Master Highway Specifications. Advanced paving techniques The Bidbid-Sur project is the first highway in Oman to follow the Performance Grading System and incorporate hot mix asphalt polymer modified bitumen (PMB). PMB is modified bitumen, which is obtained by adding different polymers to the raw bitumen. The addition alters bitumen’s chemical and physical properties, leading to a product that performs adequately much better than conventional bitumen across the spectrum of prevailing site conditions. The modified behavior of PMB allows it to retain sufficient high stiffness at high service temperatures, thus reducing rutting and shoving potential. 20