Many changes have occurred in the pavement marking industry in the past 20 years, especially the commercialization of polymeric nonshrink binders (epoxy, polyester) as durable striping materials. These materials are normally applied at thicknesses between 15 and 20 mils. Thermoplastic materials are used with application techniques andresin systems unknown 20 years ago. These materials are applied at thicknesses between 40 and 125 mils. It became apparent that as striping line durability and net line thickness increased, glass bead characteristics had to change. The extended durability of these films has shown the need for bead surface treatments that improve bead adherence to the binders. The rheology and wet film application of these new materials indicate a need for a large-diameter glass bead. Useof larger beads fits the theoretical requirement of bead embedment and binder thickness for optimum retroreflectivity. The author explains that when pavement markings are viewed as a system (i.E., Bead size and surface treatment are compatible with a specific striping material), improved reflective performance can be obtained with the added benefit of wet pavement/nighttime reflectivity. This paper appears in transportation research record no. 1230, Work-zone traffic control and tests of delineation material.
Abstract