Case Study—Delhi International Airport Phase 3 Expansion Performance Based Mix Design for Bituminous Surface Course

The Phase 3 expansion of Delhi International Airport involved brownfield construction of major airside infrastructure, imposing constraints on engineering and construction planning. A major challenge was posed for finalization of an appropriate mix design of the bituminous surface course (P-401) and selection of the appropriate binder: polymer modified bitumen (PMB). The mix design had to ensure workability and compactibility through the limited construction time-window, in consideration of the increased transit time, due to the stringent security arrangements for airside delivery of the hot-mix produce from the plant on landside and the weather factors. There was always a competing requirement for stiffness of the mix to be achieved with a stiffer binder versus the lower viscosity requirement for workability. The same was achieved with performance-based selection of the binder and mix design incorporating dynamic shear rheometer (DSR) tests of the binder and compactibility, rutting, and fatigue performance testing of the mix. Aggregate grading design formed an integral part with friction requirements for the surface course being another important parameter to be achieved. The paper presents the process and testing regime for achieving a high-performing asphalt surface course mix for the flexible aircraft rated pavements for the project.