302SUBBASE

302.01Description

This work shall consist of a foundation course of selected materials, placed and compacted on a prepared subgrade in accordance with 105.03.

Subbase for PCCP shall consist of a 3 in . layer of coarse aggregate No. 8 as the aggregate drainage layer placed over a 6 in. layer of coarse aggregate No. 53 as the separation layer. Dense graded subbase shall consist of a 6 in. layer of coarse aggregate No. 53. 10

MATERIALS

302.02Materials

Materials shall be in acco rdance with the following:

Coarse aggregate No. 8 used as an aggregate drainage layer shall consist of 100% 20 crushed stone or ACBF.

CONSTRUCTION REQUIREMENTS

302.03Preparation of Subgrade

Subgrade shall be prepared in accordance with 207.

302.04Temperature Limitations

Aggregate shall not be placed when th e air temperature is less than 35°F. Aggregate shall not be placed on a frozen subgrade. Frozen aggregate shall not be 30 placed.

302.04

302.05Spreading

Aggregate shall be spread in uniform lifts with a spreading and leveling device approved by the Engineer. The spreading and leveling device shall be capable of placing aggregate to the depth, width, and slope specified. The compacted depth of each lift shall be a minimum of 3 in. and a maximum of 6 in.

Aggregate shall be handled and transported to minimize segregation and the loss of moisture. In areas inaccessible to mechanical equipment, approved hand spreading 40 methods may be used.

The moisture content of the aggregate shall be between 4% and the optimum moisture content when the ag gregate is delivered to the project. Water shall not be added to the aggregate on the grade.

302.06Compacting

Subbases shall be compacted as follows:

Compaction shall be in accordance with 301.06.

All displacement or rutting of the aggregate separation layers shall be repaired prior to placing subsequent material.

Compaction shall consist of two passes with a vibratory roller before trimming, and one pass with the same roller in static mode after trimming. A vibratory roller shall be equipped with a variable amplitude system, a speed control device, and have a minimum vibration frequency of 1,000 vibrations per minute. A roller in accordance 60 with 409.03(d)4 may be used.

Construction traffic shall not be allowed on the aggregate drainage layer, except where placement of the PCCP is restricted. Exceptions shall be subject to approval by the Engineer. Displacement or rutting of the aggregate drainage layers shall be repaired prior to placing subsequent material.

In areas inaccessible to standard size compacting equipment a specialty roller/compactor in accordance with 409.03(d)7 shall be used.

302.07Checking and Correcting Subbase

The top of each aggregate course shall be checked transversely and all deviations in excess of 1/2 in. shall be corrected. If additional aggregate is required, the course shall be remixed and recompacted.

302.08Method of Measurement

Subbase for PCCP or dense graded subbase will be measured by the cubic yard based on the theoretical volume to the neat lines as shown on the plans. The quantity 302.05

shown in the Schedule of Pay Items will be adjusted if it is shown to be different by more than 2% of the measured quantity. 80

302.09Basis of Payment

The accepted quantities of subbase for PCCP or dense graded subbase will be paid for at the contract unit price per cubic yard, complete in place.

Payment will be made under:

Pay Item Pay Unit Symbol

Dense Graded Subbase .............................................................. CYS 90 Subbase for PCCP ..................................................................... CYS

The cost of compacting, water, aggregate placed outside neat lines as shown on the plans, and necessary incidentals shall be included in the cost of the subbase.