15 May 2001
mixture in a few minutes. Results indicate that this procedure is more accurate than the conventional
extraction test, but the aggregate gradation is not determined by this test. Therefore, extraction tests
must also be conducted to determine the aggregate gradation.
(c) Asphalt content can be determined with the Ignition Method in accordance with ASTM
PS 090. The asphalt content obtained may be more accurate than that obtained by the conventional
extraction method. The aggregates remaining after the asphalt binder is burned off may be used for
gradation purposes; however, there is a correction factor that must be determined for each type of
aggregate and gradation used.
(3) Hot-bin gradations. Hot-bin gradation tests should be made on the aggregate in the fine
bin at least twice daily during operation. Hot-bin gradations shall be determined on all bins in
conjunction with sampling of the pavement mixture. Washed sieve analyses shall be determined
(4) Construction control. Well-designed mixes can be compacted by adequate field rolling to
about 98 percent or greater of the density obtained by compacting specimens with previously specified
laboratory procedures. Asphalt intermediate, base course, or surface course mixes shall be rolled to the
density specified in applicable Department of the Army and Air Force guide specifications.
(5) Pavement sampling. Samples for determining pavement density and thickness may be
taken either with a coring machine (at least 100 millimeters, (4 inches) nominal diameter) or by cutting
out a section of pavement at least 100 millimeters (4 inches) square with a concrete saw. These
samples should include the entire thickness of the pavement. Density samples of each day's production
should be taken and delivered to the project laboratory by noon of the following day, and the density
determinations made by the end of the day. Any changes in placing technique necessary to obtain the
required density can be made before a large amount of pavement is placed.
(6) Testing pavement samples.
(a) Pavement samples shall be prepared for testing by carefully removing all particles of
base material or other foreign matter. All broken or damaged edges of sawed samples for density tests
shall be carefully trimmed from the sample. Thickness measurements shall be made before separating
the sample into layers. A sample consisting of an intermediate course and surface course shall be split
at the interface of these layers before testing. The density of the sawed samples shall be determined by
weighing in air and in water as previously described. Samples from which density measurements are
desired shall be discarded if damage is apparent. Additional samples will be taken from the same
(b) Nuclear gages are currently being used to check density of hot-mix asphalt. This
method is fast, but the results are often questionable. Some factors which affect the results of density
measurements with the nuclear gage are thickness of asphalt mixture, density of material below asphalt
mixture, and smoothness at test location. The nuclear gage is useful for developing roller patterns, but
density tests for acceptance should be conducted by removing samples from the pavement and
weighing in air and water.
(7) Density data. Density data obtained from specimens in the manner previously described
will be compared with the average laboratory density determined for the same lot.
(8) Pavement imperfections and probable causes. Many types of pavement imperfections
result from improper laying and rolling operations as well as from improper mixes or faulty plant
operation. These imperfections can be controlled only by proper inspection. Figure 2-10 presents the