InstroTek
13
6.
Bulk Specific Gravity (G
mb
) of Compacted Asphalt
Specimens ASTM D6752 & AASHTO T 331
The following procedure can be used as an alternative to ASTM D2726 &
AASHTO T 166 for determination of bulk specific gravity of compacted asphalt
specimens. This procedure requires that a dry compacted asphalt specimen be
placed inside a bag and vacuum-sealed with the CoreLok. The bag is then
placed underwater and a submerged weight is determined. The weight in air
and the submerged weight can be used to calculate the bulk specific gravity of
the asphalt specimen.
Note: The latest version of the GravitySuite
software can be downloaded from
our web site at www.instrotek.com/downloads.
Important: To avoid errors in submerged weight of the sample, use a large water
tank. The minimum recommended dimensions for the tank are 610(L) X460(W)
X460(D) mm (24X18X18 in). See “CoreLok Bags” on page 11 for correct bag size
usage.
Note: Make certain the sample is at room temperature and loose debris and
sharp edges are removed—use the CoreEdge Breaker to knock down the rough
specimen edges—before beginning the test.
Procedure
1.
Select Program #1. In Program #1, the Dwell time is set at the factory, thus
making sure that all trapped air is removed from the bags.
2.
Place enough filler plates inside the CoreLok to ensure the specimen will
not impede the machine lid from closing. You will need the sliding plate
for this test so this height will also need to be taken into account.
3.
Select an appropriate size bag (see above for core size information).
Inspect the bag for holes or stress points. Do not use the bag if you find
holes or stress points.
4.
Weigh the bag, record the total weight in column A of the Bulk Specific
Gravity Data Collection Table
(pg. 17).
5.
Weigh the dry sample and record the sample weight in column B.
6.
Place the empty bag inside the CoreLok chamber.
7.
Gently place the core inside the bag ensuring the core is resting on top of
the sliding plate while taking care to not puncture the bag.
8.
Place the bag opening over the seal bar with approximately 1” overlap
and close the chamber door. After the vacuum and sealing operation,
the chamber door will open. See
“SEAL”
on
page 11
for additional
information.
