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CANNON Instrument Company | Beam Preparation 37
Specimen Pouring
Follow the steps below to pour a specimen for testing in the Bending Beam Rheometer.
1. Heat the asphalt binder sample.
Heat the asphalt sample in an oven to a temperature not exceeding 165 ° C to 180 °C (329 °F to
356 °F) until it has become sufficiently fluid to pour. The temperature should be sufficient to
produce a coefficient of viscosity from 100 to 200 cSt. The time and temperature required depends
on the size of the sample and the hardness of the asphalt. For virgin asphalt, and for a sample of
about 50 gm (3 oz. tin), 60 minutes at 135 °C (275 °F) is generally sufficient.
Caution: Take appropriate precautions when handling hot asphalt.
The sample should be stirred occasionally to aid heat transfer and to assure uniformity. But avoid
excessive stirring to prevent oxidative hardening. After bringing sample to the required
temperature, stir the sample until it is homogeneous and free of air bubbles.
2. Pour the asphalt.
Pour the asphalt into the mold, starting at one end and moving slowly toward the other. Hold the
sample container 25 mm to 40 mm (1” to 1.5") from the mold and pour continuously until the mold
is completely filled. Try to fill the mold in one pass, as pouring the beam in several passes may
entrap air gaps or bubbles in the specimen.
Overfill the molds slightly with asphalt so that the excess can be trimmed after the asphalt cools.
Overfilling is necessary so that the demolded specimen has square edges and uniform width. After
pouring the specimen, cool the filled mold at room temperature (about 20 °C or greater) for 45 to 60
minutes.
3. Trim the specimen.
After the specimen has cooled, use a hot knife or a heated spatula to trim the upper face of the
specimen so that it is level with the top of the mold. Any excess asphalt on the side bars should be
carefully cleaned with the hot knife or other appropriate sharp-edged instrument.
Note: It’s very important to trim and clean the top side of the mold. If the width
of the specimen is more than 12.7 mm (¼”) it will not fit correctly on the device
supports. If the upper side of the mold is not cleaned carefully the specimen will
adhere to the side bars, making removal difficult.