(A) Composition The silica content of the glass beads shall be at least 60%. Manufacture the beads from 100% recycled non-pigmented glass from a composition designed to be highly resistant to traffic wear and to the effects of weathering. All Section 1087 standard intermix and drop-on glass beads shall be manufactured using 100% North American recycled glass cullet. All intermixed and drop-on glass beads shall not contain more than 75 ppm arsenic or TABLE 1087-2 GLASS BEAD GRADATION REQUIREMENTS Sieve Size Gradation Requirements Minimum Maximum Passing #20 100% Retained on #30 5% 10% Retained on #50 40% 80% Retained on #80 15% 40% Passing #80 0% 5% Retained on #200 0% 5% 200 ppm lead. (B) Physical Characteristics Use glass beads that are colorless, clean, transparent and free from milkiness, excessive air bubbles, skins and foreign objects. Use glass beads with a minimum refractive index of 1.50 when tested by the liquid immersion method at 77°F ± 9°F in accordance with ASTM D1214 using the Becke Line Method or an equivalent method. Use glass beads that are spherical in shape and essentially free of sharp angular particles or particles showing surface scarring or scratching. All intermixed and drop-on glass beads shall comply with NCGS § 136-30.2 and 23 USC § 109(r). (C) Gradation & Roundness Use drop-on and intermixed glass beads in all pavement markings with at least 80% true spheres when tested in accordance with ASTM D1155. Drop-on and intermixed glass beads used on any pavement markings shall meet Table 1087-2. (D) Chemical Resistance Conduct the following chemical resistance test on all glass beads: Place 3 to 5 g portions of the same glass bead batch to be tested in three separate glass beakers or three porcelain dishes. Cover one sample with distilled water, cover the second sample with 3N solution of sulfuric acid and cover the third sample with 50% solution of sodium sulfides. After one hour of immersion, examine the glass bead samples microscopically for evidence of darkening or frosting. All three samples shall show no evidence of darkening or frosting. (E) Moisture Resistance Conduct the following moisture resistance test on drop-on glass beads: Place a 2 lb. minimum sample of glass beads in a clean, washed cotton bag with a thread count of 50 warp, 50 woof. Immerse the bag containing the sample in a container of water for 30 seconds or until the water covers the spheres, whichever is longer. Remove the bag from water and force excess water from the sample by squeezing the bag. Suspend the bag and allow to drain for 2 hours at room temperature 70°F to 72°F. Then mix the sample in the bag by shaking thoroughly. Transfer the sample slowly to a clean dry glass funnel having a stem of 4 inches in length with 1/4 inch inside diameter. The entire sample shall flow freely through the funnel without stoppage. When first introduced in the funnel, if the spheres clog, it is permissible to lightly tap the funnel to start the flow.
