cover aggregate is desired. Where cooler
temperatures are anticipated, preference should be
given to the use of MC- or RC-3000 in very warm
climates when work will be performed during periods
of high ambient temperature.
Emulsified asphalt grades RS-1, RS-2, CRS-1, and
CRS-2 are suitable for seal coat applications.
Emulsions are better suited to coat aggregate when
the aggregate moisture content is over 1 percent but
less than 3 percent. The following considerations
should be included in the evaluation of alternate
grades to be specified for the project:
a. Local practice and experience, as well as
availability and cost of various grades within the
area.
b. The rapid-setting emulsions, particularly the
cationic types, are effective when damp aggregates
must be used.
c. Where cooler temperatures are anticipated,
consider the use of CRS-1 and CRS-2 grades.
d. Anionic emulsions provide better adhesion to
basic aggregates such as limestone, while cationic
emulsions are better with acidic aggregates such as
silicates.
Asphalt cement penetration grades 120-150 and
200-300, in order of preference, are suitable for
most normal seal coat applications. Where cooler
temperatures are anticipated, preference should be
given to the use of 200-300 grade.
Tar grades RT-9 and RT-8 are suitable for most
normal seal coat applications. Where cooler
temperatures are anticipated, consider the use of
grades RT-6 and RT-7. Consider the use of grades
RT-10 and RT-11 in very warm climates when work will
be performed during periods of high ambient
temperature.
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Bituminous material shall conform to [AASHTO M 20] [AASHTO M 81] [AASHTO M
82] [AASHTO M 226] or [ASTM D 490] [ASTM D 946] [ASTM D 977] [ASTM D 2027] [
ASTM D 2028] [ASTM D 2397] [ASTM D 3381], [grade [_____]] [penetration
grade [_____]].
2.2
AGGREGATE FOR SEAL COAT
**************************************************************************
NOTE: The aggregate gradation to be used will be
retained in Table I and the remaining gradations
deleted.
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Aggregate shall consist of crushed stone, crushed gravel, crushed slag,
SECTION 02785
Page 12
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