UFC 3-250-03
15 May 2001
(4) Asphalt contents for specimens. The quantity of asphalt required for a particular aggregate
is very important to assure satisfactory performance. The procedures to follow are described in (5)
(Selection of design compaction method) below. An estimate for the optimum amount of asphalt based
on total weight of mix is normally made in order to start the laboratory tests. Laboratory tests usually are
conducted for a minimum of five asphalt contents: two above, two below, and one at the estimated
optimum content. Incremental changes of 1 percent of asphalt may be used for preliminary work, but
increments of 0.5 percent are generally used when the optimum asphalt content can be estimated and
for final design.
(5) Selection of design compaction method. The Department of the Army and Air Force allow
two methods of compacting asphalt paving mixtures in the laboratory--the Marshall and the Gyratory
Testing Machine methods. The procedures for conducting the Marshall mix design tests are described
in CRD-C 649. The procedure for gyratory compaction is given in CRD-C 651 or the standard testing
method of ASTM D 3387 except as follows:
(a) Use 101.6 millimeter (4-inch) diameter molds in lieu of 152.4 millimeter (6-inch) molds
when Marshall stabilities and flows are to be determined.
(b) Use mixing and compaction temperature requirement as given in CRD-C 649.
(c) The Gyratory Testing Machine setting and equivalent compaction requirements shall
be as listed in table 2-5.
Table 2-5
Traffic Type and Gyratory Compaction Requirements
Type of Traffic
Gyratory Compaction Requirement
Tire pressures less than
Gyratory compaction at 690 kPa
690 kPa (100 psi)
(100 psi), 1-degree, 30 revolutions (50 blows Marshall
equivalent)
Tire pressures 690 kPa
Gyratory compaction at 1,380 kPa
(100 psi) and greater but less
(200 psi,) 1-degree, 30 revolutions (75 blows Marshall
than 1,586 kPa (230 psi)
equivalent)
Tire pressures 1,586 kPa
Gyratory compaction at 1,655 kPa
(230 psi) and greater
(240 psi), 1-degree, 60 revolutions (preferred but not
mandatory for Army and Air Force airfields)
In the event an airfield pavement is to be subjected to aircraft with tire pressures of 1,586 kPa (230 psi)
or more, the Gyratory Testing Machine (GTM) method is mandatory for Army airfield pavements and is
preferred but is not mandatory for Air Force airfield pavements. If the GTM method is used for design, it
should also be used for control testing. If the GTM cannot be used for control testing, the Marshall
apparatus can be used by developing a correlation between the GTM and Marshall specimens for the
job mix. Care should be taken to insure that excess breakage of the aggregate particles does not occur
during Marshall compaction.
(6) Tabulation of data. After the laboratory design method has been selected and test
specimens have been prepared, data should be tabulated on forms similar to those shown in CRD-C
649 and CRD-C 650 if the Marshall procedure is used. These forms, along with the forms shown in
CRD-C 651, are normally used for the gyratory procedure. Arranging data as shown in table 2-6 will
facilitate tabulation of specimen test property data and is preferable to similar but less complete methods
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