DETERMINING COATING &STRIPPING OF
This IM is intended to provide the procedure for determining the ability of cutback or emulsified asphalt to retain a film on aggregate in the presence of water.
· Container for mixing having rounded corners, such as an 8 or 16 oz. (240 or 480 ml) seamless ointment tin
· Balance with a capacity of at least 200 grams and accurate to 0.1 gram
· Spatula with a stiff blade approximately 1 in. (25 mm) in width and 4 in. (100 mm) in length
· Oven capable of maintaining any temperature between 140°F and 275°F ± 2°F (60°C and 135°C ± 1°C)
· Two sieves, one having 3/8 in. (9.5 mm) size mesh and the other No. 4 (4.75 mm) size mesh.
· Glass beaker with 20 oz. (600 ml) capacity
2. Add 5.5 ± 0.2 grams of cutback asphalt; preheat when necessary to the temperature specified in Table 1.
3. Mix the cutback and aggregate vigorously with the spatula for 2 minutes. MC-800 and MC-3000 grades may be warmed over a hot plate during the mixing period just sufficiently to permit effective mixing, but not above the temperature limits in Table 1.
4. Oven-cure the coated aggregate in its original container for 2 hours at 140°F (60°C).5.After curing, remix with the spatula while the mixture cools to room temperature or until the asphaltic residue ceases to drain off the aggregate. Coating of the aggregate must be complete. No bare spots are permissible.
5. Transfer the coated aggregate to the 20-oz. glass beaker. Cover immediately with about 16 oz. of distilled water at room temperature. Allow the coated aggregate to remain immersed in the water for 16 to 18 hours at room temperature.
6. Without disturbing or agitating the coated aggregate, remove any film floating on the water surface. Illuminate the specimen by a flashlight or shaded lamp, positioned to eliminate glare from the surface of the water. By observation through the water from above, visually determine if the percent of retained film on the aggregate surface is above or below 95%. Any thin brownish, translucent areas are considered fully coated.
This procedure is identical to the method of coating standard aggregate with cutback asphalt with the following exceptions:
1. Report the remaining coated area as “Above 95%” or “Below 95%.”
Cutback Asphalt Temperature for Mixing
MC-30 and MC-70 Room temperature
MC-250 95°F ± 5°F (35°C ± 2.5°C)
MC-800 125°F ± 5°F (52°C ± 2.5°C)
MC-3000 155°F ± 5°F (68°C ± 2.5°C)