ITEM 302 ASPHALT CONCRETE BASE
302.01
Description
302.02
Composition
302.03 Mixing
302.04
Spreading and Finishing
302.05
Spreading and Surface Tolerances
302.06 Basis of
Payment
302.01 Description. This work consists of
constructing a base course of aggregate and asphalt binder, mixed in a central
plant and spread and compacted on a prepared surface.
The
requirements of Item 401 apply, except as modified
by this specification.
A. General. Furnish a mixture that
conforms to the following gradation:
Sieve Size |
Total Percent Passing |
|
2 inch |
(50 mm) |
100 |
1 1/2 inch |
(37.5 mm) |
85 to 100 |
1 inch |
(25.0 mm) [1] |
68 to 88 |
3/4 inch |
(19.0 mm) [1] |
56 to 80 |
1/2 inch |
(12.5 mm) [1] |
44 to 68 |
3/8 inch |
(9.5 mm) [1] |
37 to 60 |
No. 4 |
(4.75 mm) |
22 to 45 |
No. 8 |
(2.36 mm) |
14 to 35 |
No. 16 |
(1.18 mm) |
8 to 25 |
No. 30 |
(600 µm) |
6 to 18 |
No. 50 |
(300 µm) |
4 to 13 |
No. 200 |
(75 µm) |
2 to 6 |
[1]
Provide aggregate to retain a minimum of 7 percent of the material on
each of these sieves. This requirement applies to the gradation of the JMF and the mix production according to Item 403.
In the design of the
asphalt concrete base, the requirements of Item 441 apply,
except as follows:
The Contractor may
use reclaimed asphalt concrete pavement according to 401.04. Should problems with proper
coating or other material issues related to the use of
reclaimed asphalt concrete pavement be evident, the Laboratory may limit
reclaimed asphalt concrete pavement to 30 percent. In this case virgin
binder content will be adjusted by the Laboratory.
Add hydrated lime in
the dry form at a rate of 0.75 percent by the dry weight of aggregate for
asphalt concrete base, if antistrip additive is
required and hydrated lime is used.
Design the asphalt
concrete base to yield 4.0 percent air voids and the following properties:
Property |
Acceptable Range of Values |
|
Minimum |
Maximum |
|
Binder Content, % of total mix |
2.0 [Virgin] |
6.0[Total] |
Stability, lb
(N), 70 blow |
3000 (13,345) |
-- |
Flow, 0.25 mm, 70 blow |
-- |
28 |
Voids in Mineral Aggregate % |
12.0 |
-- |
Use equipment that
meets the requirements of a Level 3 Laboratory as specified in Supplement
1041. Ensure that the following equipment is designed and
manufactured to prepare and test a Marshall specimen with a 6.0-inch (152.4 mm)
diameter and a 3.75 ±0.05 inch (95 ±1.3 mm) height:
1.
Specimen mold assembly
2.
Specimen extractor
3.
22.5-pound (10 kg) compaction hammer.
4.
Compaction pedestal specimen mold holder.
5.
Marshall test apparatus.
Produce batches of
asphalt concrete base in the amount that will result in a compacted specimen
3.75 ±0.05 inch (95 ±1.3 mm) in height. This amount is about 4050 grams.
B. Compaction of Specimens. Fill the mold with asphalt concrete base by
placing approximately one-half of the batch in the
mold and spading it vigorously with a heated spatula or trowel 15 times around
the perimeter and ten times over the interior. Place the second half of
the batch in the mold and spade the mixture in the same manner.
Compact the specimen
on both sides with 70 blows.
C. Stability Correlation Ratios. Convert measured stability values for specimens
that depart from the standard 3.75-inch (95 mm) thickness to an equivalent
3.75-inch (95 mm) value by multiplying the stability value by the appropriate
correlation ratio as follows:
Approximate Thickness of Specimen, inches (mm) |
Correlation Ratio |
|
3 1/2 |
(89) |
1.12 |
3 9/16 |
(90) |
1.09 |
3 5/8 |
(92) |
1.06 |
3 11/16 |
(94) |
1.03 |
3 3/4 |
(95) |
1.00 |
3 13/16 |
(97) |
0.97 |
3 7/8 |
(98) |
0.95 |
3 15/16 |
(100) |
0.92 |
4 |
(102) |
0.90 |
302.03 Mixing. Conform to the requirements of 301.03.
302.04 Spreading and Finishing. Ensure
that the compacted depth of any one layer is a minimum of 4 inches
(100 mm) and a maximum of 7.75 inches (190 mm). Ensure that the
temperature of the mixture when delivered to the paver is a minimum of 250 °F
(120 °C) if a hot mix asphalt and 230 °F (110 °C) if a warm mix asphalt
according to 402.04. Ensure the
temperature of the mixture is sufficient for the roller coverage to be
effective in compacting the mixture
302.05 Spreading and Surface Tolerances. Conform to the
requirements of 301.05.
302.06 Basis of Payment. The
Department will pay for accepted quantities, complete in place, at the contract
price as follows:
Item
Unit
Description
302
Cubic
Yard
Asphalt Concrete Base
(Cubic Meter)