Use of Glass Grid and SAMI as Reinforced Interlayer System in Runway

Abstract

Runways are made of rigid as well as flexible pavement. Generally, flexible pavement is sandwiched between two rigid ends. Traffic loading, age hardening, or temperature cycling typically cause fatigue and reflective cracking in flexible pavement. When cracking is present, the traditional remedy has been to apply thicker asphalt overlays. Reinforcement using an interlayer system has been demonstrated as a multipurpose solution to improve the performance, extend service life and thus to reduce maintenance cost of runway pavement. Among a large number of existing interlayer systems, glass grid along with SAMI (Stress Absorbing Membrane Interlayer) have shown effective use in pavement reinforcement with a hot mix asphalt overlay. Glass grids are composed of series of fiberglass strands coated with an elastomeric polymer and formed into a grid structure. However, SAMI is a layer of PMB (polymer-modified bitumen), which shall be laid over glass grid surface, together with a covering of aggregate chips, spread, and rolled to retard reflection cracking. This paper presents the characteristics (physical properties) of glass grid fiber and SAMI layer, methodology of laying of the layers, their theoretical aspects, field tests for checking their adhesiveness, etc.