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Bases & Subbases (300-399)

304Section 304

CO · 2023 Standard SpecificationsBook pages 335336View official source ↗

304.01 304-1 DIVISION 300 BASES AGGREGATE BASE COURSE DESCRIPTION

304.01 This work consists of furnishing and placing one or more courses of aggregate and

additives, if required, on a prepared subgrade. MATERIALS

304.02 Aggregate. The aggregates shall meet the requirements of subsection 703.03.

Acceptance will be based on random samples taken from each lift.

304.03 Commercial Mineral Fillers. Portland cement shall conform to subsection 701.01.

Hydrated lime shall conform to subsection 712.03. CONSTRUCTION REQUIREMENTS

304.04 Placing. If the required compacted depth of the aggregate base course exceeds 6

inches, it shall be constructed in two or more layers of approximately equal thickness. The maximum compacted thickness of any one layer shall not exceed 6 inches. When vibratory or other approved types of special compacting equipment are used, the compacted depth of a single layer may be increased to 8 inches upon request, provided that specified density is achieved, and written approval is given.

304.05 Mixing. The Contractor shall mix the aggregate by methods that ensure a thorough and

homogenous mixture.

304.06 Shaping and Compaction . Compaction of each layer shall continue until a density of at

least 95 percent of the maximum density has been achieved as determined per AASHTO T 180 as modified by CP 23. The moisture content shall be at plus or minus 2 percent of optimum moisture content. The surface of each layer shall be maintained during the compaction operations so that a uniform texture is produced, and the aggregates are firmly keyed. Moisture conditioning shall be performed uniformly during compaction. Compaction of each reclaimed asphalt pavement aggregate layer shall continue until a wet density of at least 95 percent of the maximum wet density when determined per a one-point AASHTO T 180, Method D test has been achieved. The surface of the base course will be tested with a 10- foot straightedge, or other approved device. The surface shall be tested before the application of any primer or pavement. The variation of the surface from the testing edge of the straightedge between any two contacts with the surface shall not exceed 1/2 inch. All irregularities exceeding the specified tolerance shall be corrected to the satisfaction of the Engineer at no additional cost to the Department. The above compaction and straightedge requirements shall not apply to shoulder gravel. Compaction of shoulder gravel shall be accomplished by wheel rolling, as directed. 304.07 304-2 METHOD OF MEASUREMENT

304.07 Aggregate base course will be measured by the ton, or by the cubic yard compacted

in place. BASIS OF PAYMENT

304.08 The accepted quantities of aggregate base course, of the class specified, will be

paid for at the contract price bid per ton or per cubic yard, as shown in the bid schedule. Payment will be made under: Pay Item Pay Unit Aggregate Base Course (Class ) Ton, Cubic Yard Aggregate Base Course (RAP) Ton, Cubic Yard Water will not be measured and paid for separately but shall be included in the work. Commercial mineral fillers, when used, will be measured and paid for per Section 307 or as provided in the Contract. 306.01 306-1 SECTION 306 RECONDITIONING DESCRIPTION

306.01 This work consists of blading, shaping, wetting, and compacting the existing subgrade

with moisture and density control. CONSTRUCTION REQUIREMENTS

306.02 The top 6 inches of the existing subgrade shall be reconditioned by blading and rolling.

Sufficient water shall be added to meet the density requirements as specified in the Contract. The reconditioned surface shall not vary above or below the lines and grades as staked by more than 0.08 foot. The surface shall be tested for smoothness and density before the application of any base course material. Where asphalt -surfacing materials are to be placed directly on the subgrade, the subgrade plane shall not vary more than 0.04 foot. All irregularities exceeding the specified tolerance shall be corrected to the satisfaction of the Engineer at no additional cost to the Department. The surface shall be satisfactorily maintained until base course has been placed. METHOD OF MEASUREMENT

306.03 Reconditioning will be measured by the square yard of subgrade, including auxiliary

lanes, and shall include blading, shaping, scarifying, compacting the subgrade, finishing, and maintenance of the finished surface. BASIS OF PAYMENT

306.04 The accepted quantities of reconditioning will be paid for at the contract unit price for

reconditioning. Payment will be made under: Pay Item Pay Unit Reconditioning Square Yard Water will not be measured and paid for separately but shall be included in the work.

Source: Colorado Standard Specifications for Road and Bridge Construction, 2023 Edition. Pages 335336 of 943.