Embedment characteristics of drop-on moistureproofed and uncoated glass spheres and their subsequent retroreflectivity were evaluated subjectively in various types of hot-applied thermoplastic trafficmarkings by illuminating test panels in a dark room. In all of the hot-applied thermoplastic traffic marking types tested, uncoated drop-on spheres were generally overembedded because of positive wettingof the spheres by the thermoplastic traffic marking, and their retroreflectivity varied. The use of moistureproofed drop-on spheres in various thermoplastic traffic marking types resulted in optimal beadembedment with subsequent excellent retroreflectivity. The optimal rate of glass sphere application in all of the thermoplastic markingtypes was found to be 10 lb of moistureproofed glass spheres per 100 sq ft -- this rate enhanced retroreflectivity, bead embedment, andcoverage. The retroreflectivity of the standard gradation of glass spheres may be enhanced in all of the thermoplastic types by increasing the percentage of spheres retained on u.S. Sieves 30, 40, and 50and by increasing the overall rounds from 70 to 80 percent. This paper appears in transportation research record no. 1230, Work-zone traffic control and tests of delineation material.
Samenvatting