ITEM 302 ASPHALT CONCRETE BASE

302.01 Description

302.02 Composition

302.03 Mixing

302.04 Spreadingand Finishing

302.05 Spreadingand 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.

302.02 Composition.

A. General. Furnish aggregate for the mix 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 m)

6 to 18

No. 50 (300 m)

4 to 13

No. 200 (75 m)

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 Contractormay use a maximum of 30 percent of reclaimed asphalt concrete pavement. If used, include the reclaimed material in this mix design process according to 441.03.

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 4.5 percent air voids and the following properties:

Property


Acceptable Range of Values

minimum

maximum

Binder Content, % of total mix

3

8

Stability, lb (N), 112 blow

3000
(13,345)

--

Flow, 0.25 mm, 112 blow

--

28

Voids in Mineral Aggregate,%

11.5

--

 

Use equipment that meets the requirements of a Level 2 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. Compactionpedestal specimen mold holder.

5. Marshall test apparatus.

Produce batches of asphalt concrete base of an 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. Compactionof 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 75 blows for medium traffic volumes and 112 blows for heavy traffic volumes.

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 Spreadingand 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), and is sufficient for the roller coverage to be effective in compacting the mixture.

302.05 Spreadingand Surface Tolerances. For the surface, 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 AsphaltConcreteBase
(Cubic Meter)