UFC 3-250-03
15 May 2001
(a) Aggregates for use in an asphalt mixture should be clean, hard, and durable. Angular
aggregates provide more stable pavements than do rounded aggregates. Most of the tests of
aggregates required in the design of hot-mix, hot-laid asphalt mixtures are also applicable to the cold-
laid type. Table 6-5 lists the aggregate gradation requirements. These gradations correspond to those
recommended in this text for hot-mix, hot-laid asphalt mixtures. The gradations given in table 6-5
correspond to those given in table 2-1 for hot-mix asphalt.
Table 6-5
Aggregate Gradations for Plant-Mix Cold-Laid Asphalt Pavements
Percent Passing Sieve by Weight
12.7 Millimeter
9.5 Millimeter
Sieve Size
(1/2-inch) Maximum
(3/8-inch) Maximum
12.7 mm (1/2 inch)
100
--
9.5 mm (3/8 inch)
86 9
100
4.75 mm (No. 4)
66 9
85 9
2.36 mm (No. 8)
53 9
71 9
1.18 mm (No. 16)
41 9
57 9
600 Fm (No. 30)
31 9
43 9
300 Fm (No. 50)
21 8
31 8
150 Fm (No. 100)
13 6
19 6
75 Fm (No. 200)
4.5 1.5
63
(b) Generally, aggregates for paving mixes must be combined from two or more
stockpiles. The decision of whether to add a mineral filler sometimes required depends on the amount
of filler naturally present in the aggregate. Mathematical equations are available for making such
combinations, but are not presented in this manual because they are lengthy and trial-and-error
procedures are normally easier. The method of combining stockpile sample gradations is described in
paragraphs Proportioning of stockpile samples and Proportioning of bin samples under HOT-MIX
chosen from table 6-1 for the project specifications and shall present a smooth curve when plotted with
sieve size versus percent passing.
(2) Tests on asphalt cement.
(a) The specific gravity of the asphalt cement must be known to determine the percent by
volume of bituminous materials in the mix. Because only the residual asphalt will be used in calculating
the percent binder, the amount of residual asphalt cement in cut-back asphalts and asphalt emulsions
will be determined as specified in ASTM D 402 and ASTM D 244 for cut-back and emulsified asphalts,
respectively. The specific gravity of the residual asphalt shall be determined as described in
ASTM D 70.
(b) Plant-mix cold-laid pavements may be made with asphalt cement and liquefier, cut-
back asphalts or emulsified asphalts. A cut-back asphalt can be produced, usually for small or remote
projects, by using kerosene to liquify an asphalt cement. The type of asphalt cement used to make this
liquid binder can be easily varied to meet various climate conditions. The cut-back binder produced can
have a relatively long shelf life, depending on the amount of cut-back material or kerosene that is added.
6-6
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