UFC 3-250-03
15 May 2001
(b) Theoretical maximum specific gravity of mixture. The theoretical maximum specific
gravity can be determined by the test method described in ASTM D 2041. This test is conducted on the
asphalt mixture and does not require a specific gravity test on the individual aggregates. The theoretical
maximum specific gravity can be used to back calculate the effective specific gravity of the aggregate.
This method can be used for aggregate blends having any amount of water absorption.
(3) Abrasion and impact resistance of coarse aggregate. The determination of percent loss for
coarse aggregates may not be necessary if the aggregate has been found satisfactory by previous tests
and/or performance. However, coarse aggregates obtained from new or doubtful deposits shall be
tested for resistance to degradation by evaluating the conformance to specification requirements for
percent loss as measured using the Los Angeles Machine (ASTM C 131).
(4) Soundness test. The soundness test is used where damage from freezing is expected to
be a problem. The soundness test should not be performed on aggregate that has been found
satisfactory by previous tests or performance data. However, aggregate obtained from new or doubtful
deposits will be tested for conformance to specification requirements using the sodium sulfate or
magnesium sulfate solution tests (ASTM C 88).
(5) Percent crushed pieces. The percentage of crushed pieces in both the coarse aggregate
and fine aggregate fractions must be sufficiently high to promote stability in hot-mix asphalt mixture. A
description of a proper crushed face and the required percentage of crushed aggregate particles shall be
specified in the contract specifications.
(6) Particle shape. The particle shape of crushed aggregates is required to be essentially
cubical. Flat and elongated aggregate particles are susceptible to breakage under compaction and
subsequent traffic. The quantity of flat and elongated particles shall be tested for conformance to
specification requirements using ASTM D 4791.
(7) Natural sand content. Natural sand is defined as any fine aggregate material other than
that produced by mechanically crushing larger rocks and aggregates. Natural sands tend to be rounded
particles which, when used in excess, can cause instability in the hot-mix asphalt mixture. For airfield or
high-pressure mixtures the percentage of natural sand shall not exceed 15 percent of the combined
weight of the coarse aggregate, fine aggregate, and the material passing the 75 Fm (No. 200) sieve.
This percentage can increase to 25 percent for roadway (low-pressure) mixtures. The limitation on the
percentage of natural (uncrushed) sand in the mixture assures a strong and stable pavement under
traffic.
(8) Fine aggregate effect. The uncompacted void content (C 1252, Method A) will help define
the angularity of the fine aggregate. The lower limit should be 45, unless local experience indicates that
aggregates with a lower value can provide good performance. Generally, a value of 43 should be the
lowest value accepted.
(9) Voids in the mineral aggregate (VMA). The volume of intergranular void space between
the aggregate particles of a compacted paving mixture that includes the air voids and volume of the
asphalt not absorbed into the aggregates.
(10) Combining aggregates. When asphalt mixtures are produced, aggregates from two or
more sources must be combined. Methods and procedures described in this manual will permit
determination of the most suitable aggregate blend available and will prescribe the proper asphalt
content for the particular aggregate blend determined to be the most suitable. Whenever an asphalt
mixture does not meet established criteria, either the gradation of the aggregate must be improved,
another aggregate must be used, or the asphalt content must be modified. The choice as to
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