performed during the design stage to validate
mixture proportions and to evaluate relative
durability of the concrete produced.
Retain the bracketed requirement for washing coarse
aggregate if aggregates in the area require it. Add
the requirement to use a log washer or other
specific equipment if experience in the area shows
the need. Delete if not needed. It is permissible
to list certain aggregate sources that do not
require washing, if that is appropriate. The
designer must make the decision during preparation
of specifications; do not make the Resident Engineer
decide after award if aggregates need to be washed.
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Coarse aggregate shall consist of [[crushed] [uncrushed] gravel], crushed
stone, [crushed adequately seasoned air-cooled iron blast-furnace slag;
steel furnace slag will not be permitted], [reclaimed portland cement
concrete] [or a combination thereof]. [Crushed gravel shall contain not
less than 75 percent of crushed particles by mass in each sieve size, as
determined by COE CRD-C 171.] [Aggregate used for paving compass
calibration hardstands shall be free of materials having undesirable
magnetic properties, including magnetite in granite, high-iron minerals in
traprock, and pyrite in limestone.] [Coarse aggregate used for paving
power check pads shall be limestone, dolomite, basalt or other approved
material which will not cause thermal distress from jet blast.] [Reclaimed
concrete pavement or granular base produced from required removal
operations may be used for aggregate, provided it meets all requirements
specified herein for aggregates.] Aggregates as delivered to the mixers
shall consist of clean, hard, uncoated particles meeting the requirements
of ASTM C 33 except as specified herein. [Coarse aggregate shall be
washed. Washing shall be sufficient to remove dust and other coatings.]
[Coarse aggregate shall be cleaned by processing with an approved log
washer.] [Iron blast-furnace slag conforming to the grading to be used in
the concrete shall have a compact density of not less than 1125 kg/cubic
meter 70 lb/cu. ft. determined in accordance with ASTM C 29/C 29M]. Coarse
aggregate shall not show more than 40 percent loss when subjected to the
Los Angeles abrasion test in accordance with ASTM C 131.
2.2.2.2
Particle Shape Characteristics
Particles of the coarse aggregate shall be generally spherical or cubical
in shape. The quantity of flat and elongated particles in any size group
shall not exceed 20 percent by weight as determined by the Flat Particle
Test and the Elongated Particle Test of ASTM D 4791. A flat particle is
defined as one having a ratio of width to thickness greater than 3; an
elongated particle is one having a ratio of length to width greater than 3.
2.2.2.3
Size and Grading
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NOTE: Fill in the blank according to the size
aggregate available in the project area, and the
type of paving. For thin bonded overlays, limit the
nominal maximum aggregate size to less than
one-third of the uniform overlay thickness (not
including levelling portion). Use nominal maximum
aggregate size of 37.5 mm (1-1/2 inch) whenever
SECTION 02753
Page 38
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