UFC 3-260-03
15 Apr 01
d. All-Bituminous Concrete and Flexible Overlays. Sampling of the bituminous concrete and base-
course material in all-bituminous concrete and flexible overlays will be performed as described above for
the pavement and base courses of flexible pavements. An exception is made when the all-bituminous
concrete or flexible overlay exists between two thicknesses of rigid pavement (composite pavement). In
this case, only one or two chunk samples of the bituminous concrete are needed from each test pit, since
the only test necessary on the bituminous concrete portion of the overlay is an extraction test to determine
the gradation of the aggregate and the bitumen content. Likewise, it will only be necessary to obtain a
large enough sample of the base-course portion of the flexible overlay for a gradation test.
e. Subgrade. Bag samples and undisturbed samples of the subgrade may be required. If the
subgrade is composed of a fine-grained material, a 45-kilogram (100-pound) bag sample will be sufficient;
if the subgrade is composed of a granular material, a 91-kilogram (200-pound) bag sample should be
obtained. However, if laboratory CBR tests are required, which may be the case in the evaluation of a
nonrigid overlay on rigid pavements, the bag samples of subgrade material should be increased to
204 and 272 kilograms (450 and 600 pounds) for fine-grained and granular materials, respectively.
6. LABORATORY TESTS REQUIRED. Laboratory tests are necessary to classify the various pave-
ment materials and establish their strength characteristics. These tests are outlined in the following sub-
paragraphs and the test methods are presented in appendix B. Laboratory test data may also be available
from design and construction records.
a. Rigid Pavement. Normally, samples of the rigid pavement should be used to determine the flex-
ural strength of beams or splitting-tensile strength of cores. Also, samples of the concrete should be
visually examined to determine the type of aggregate and to estimate the maximum size of aggregate.
b. Flexible Pavement and Nonrigid Overlays.
(1) Where a pavement consists of more than one course, the cores obtained for testing should
be split at the interfaces of the various courses so that each course can be tested separately. The cores
of each course should be tested in the laboratory for Marshall stability, flow, percentage of asphalt by
weight, penetration of bitumen, aggregate type, shape and gradation, specific gravity of bitumen and
aggregate, and density (CRD-C 649). If the pavement were designed according to SHRP criteria, the
cores of each course should be evaluated for percentage of asphalt by weight, aggregate gradation, and
specific gravity according to AASHTO specifications which govern the placement of SHRP mixtures. The
void in the total mix and the percentage of voids filled with asphalt should be computed from the test
results (CRD C-650, AASHTO Specifications from SHRP mixtures).
(2) Portions of the chunk samples should be used for determination of aggregate gradation,
specific gravity of bitumen and aggregate, and penetration, ductility, and softening point of the bitumen.
Other chunk samples should be recompacted as described in appendix B, and the recompacted speci-
mens should be tested for Marshall stability, flow, and density. Their voids relations should also be
computed. The stability of the cores cut from the pavement will often be lower than that of the recom-
pacted sample. A part of this difference usually is due to differences in density, since the field cores
seldom have density as high as the laboratory-compacted samples. The major part of this variation in
stability is attributed to differences in the structure of the field and laboratory samples and also to the fact
that the asphalt hardens some during reheating. Since the stability value is not the sole criterion for the
evaluation of the mix, the lack of correlation between the stability of the field and laboratory samples is not
particularly significant.
(3) No standard tests have been developed to determine resistance to spillage. However, a
small amount of jet fuel should be spilled on one of the chunks from each test pit to see if the fuel pene-
trates the samples quickly or if it "puddles" on the surface.
3-9
Previous Page
