SHRP-A-379 traducir

6. SPECIMEN PREPARATION
6.1 All test specimens must be 150 mm in diameter and 50.0 _.+2.5 mm high. Any
appropriate procedure, such as AASHTO T166, Bulk Specific Gravity of Compacted
Bituminous Mixtures, can be used to determine the specific gravity of the specimen. The
dimensions of the specimens must be accurately measured and the top and bottom faces of
the specimen must be smooth and parallel.
6.2 Clean the platens and ensure that they are dust free.
6.3 Place a pair of platens into the gluing jig provided with the shear test device,
align them and clamp them into place.
NOTE 1.--The
platens are bonded to the specimen for all tests except the volumetric and uniaxial tests.
6.4 Proportion and mix epoxy resin and hardener together in accordance with the
manufacturer's instructions.
NoTE 2.--Devcon 5-Minute Plastic Steel Epoxy Cement has been found to provide satisfactory performance
for testing conducted at 20°C and higher. For low-temperature testing (typically at 4°C), Devcon Plastic Steel Epoxy
Cement proved adequate.
6.5 Ensure that the test specimen is dust flee. Apply a thin coating of epoxy cement
(- 1.5 ram) to each end of the test specimen. Assure that the epoxy cement completely
covers the specimen end and that it is of uniform thickness.
6.6 Bond the specimen to the platens under a pressure of 30 to 40 kPa for the period
of time recommended by the epoxy cement manufacturer.
6.7 Remove the test assembly from the gluing jig. Allow the epoxy to cure for the
time period recommended by the manufacturer.
NoTE 3.--For Devcon 5-Minute Plastic Steel Epoxy, a curing time of 2 hours at room temperature is
recommended.
6.8 As required for specific tests, attach mounting screws for the horizontal LVDT(s)
to the sides of the test specimen with epoxy cement (see notes 4 and 5).
minutes.
NoTE 4.--Gluing the specimen to the platens and attaching mounting screws for the LVDT takes about 15
NoTE 5.--There are several alternative methods for mounting LVDTs. LVDTs measuring axial (vertical)
deformation are generally attached directly to the platens. Similarly, LVDTs measuring shear (horizontal)
deformation are typically mounted on blocks that are in turn attached to screws bonded to the specimen. They must
measure the difference in horizontal displacement between two points on the specimen separated by at least 40 ram.
Consult figure 5 in SHRP test method M-003 for specific LVDT mounting recommendations.
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