Cannon TE-BBR, Instruction & Operation Manual

Page: 46 / 92

CANNON Instrument Company | Beam Preparation 35
The tacking material should be a commercial, petroleum-based grease that retains its tackiness at
the pouring temperature without stiffening excessively at low temperatures. The layer should be
uniform and very thin.
The purpose of the grease is to hold the plastic strips in contact with the metal faces of the mold.
After spreading the thin film of grease, clean the sides and edges of the bars with a clean tissue
moistened with solvent to prevent grease from coming in contact with the poured asphalt.
2. Cover the greased surfaces of the three metal bars with the plastic strips.
When applying the strips, avoid entrapping air bubbles between the strips and the bars. First, locate
the wider plastic strip and align it with the greased side of the (wider) base plate, pressing it firmly
into place.
The narrower plastic strips for the side plates are made longer but should match the width of the
side plates exactly. Place these two plastic strips on top of the tacking film, and press the strips onto
the bars.
3. Debond the end pieces.
The only inner metal surfaces of the assembled mold which will not be covered by plastic are the
inner edges of the two short end pieces. To prevent asphalt from sticking to these surfaces, cover
them with a thin layer of debonding agent (CANNON recommends using a mixture of talcum powder
and glycerol) and a narrow spatula, wire or rod. Avoid spreading the mixture on the plastic surfaces.
4. Assemble the mold.
Place the end pieces at the ends of the base plate, on the face covered with the plastic sheet.
Position the two side bars on the sides of the end plates with their covered sides facing inward. Use
two rubber O-rings to hold the side bars securely to the base bar at each end of the mold.
5. Inspect the mold.
After assembling the mold, inspect it for any air bubbles or detachment between the plastic sheets
and the bars. Insert a clean metal bar 6.35 mm (0.25") thick into the mold and move it back and
forth (using sliding action) between the two end pieces. This will enable you to check that the plastic
sheets are completely attached to the bars and that the sample volume is accurate.
When the above steps have been completed, the mold is ready for pouring. After it is assembled,
keep the mold at room temperature until the asphalt is to be poured. Refer to Figure 20.