304Aggregate Base and Subbase Course

304.01 Description This work shall consist of furnishing and placing one or more

courses of aggregates on a prepared surface in accordance with the specifications in reasonably close conformity with the lines, grades, thickness and typical cross sections, as shown on the plans or established.

304.02 Aggregate Aggregates shall conform to the requirements specified in the

following subsections of Division 700 - Materials: Aggregate Base Type A & B 703.06 a Aggregate Base Type C 703.06 b Aggregate Subbase Type D & E 703.06 c Aggregate for base or subbase courses shall be material meeting the aggregate type requirements specified in the following table: Material Aggregate Type (Subsection 703.06) Base Course, Crushed 1A, B or C Subbase Course, Gravel 2D 1Will be designated on the plans 2Subbase Course, Gravel-Type E may be used below the top 9” of the subbase layer at the Contractor’s option For the various types of base and subbase, all shall conform to the gradation requirements of the contract at the time it is deposited on the roadbed. The Department will obtain samples from the roadbed for Acceptance prior to compaction. Oversized stones shall be removed from the aggregate before depositing on the roadway. Oversized stones for the various types are as follows: Type A will not pass a 2 inch square mesh sieve Type B and Type C will not pass a 4 inch square mesh sieve Type D and E will not pass a 6 inch square mesh sieve.” The top 3” of Aggregate Base Course-Type C shall consist of Recycled Asphalt Pavement (RAP) or Untreated Aggregate Surface Course-Type B. 3-2

304.03 Placing The maximum compacted thickness of any base or subbase course layer

shall not exceed 12 inches unless the Contractor demonstrates by a test section that the required compaction can be obtained. If compacted layers more than 12 inches are allowed, the Contractor shall agree to make the necessary excavations and backfilling in the course for the Resident to determine the density. When layers are constructed of differently graded aggregate, f ine grading of the lower layer will not be required except when millings are placed as the upper most layer. In this case the coarse graded base layer shall be fine graded to +/- ¾ inch and compacted to the required specification prior to placing the layer of millings. The layer of millings shall then be placed, shaped, and compacted within the tolerances specified below. Each layer of aggregate shall be placed over the full width of the section except, the Resident may authorize the Contractor to place less than full width layers, when existing traffic or other conditions restrict operations over the full width of the section. When the Contractor places material to complete the full width, the exposed edge of the previously placed aggregate shall be cleaned of all contamination before additional base or subbase aggregate is placed adjacent to it. Aggregate base and subbase courses may be placed upon frozen s urfaces when such surfaces have been properly constructed. The material as spread shall be well mixed with no pockets of either fine or coarse material. Segregation of large or fine particles will not be allowed.

304.04 Shaping, Compacting and Stabilizing Compaction of each layer of base and

subbase shall continue until a density of not less than 95% of the maximum density has been achieved for the full width and depth of the layer. The maximum density shall be determined in accordance with AASHTO T180, Method C or D, correcting for oversize particles except mixtures may have 40 percent or less retained on the ¾ inch sieve. Field density tests will be performed by the Department in accordance with AASHTO T 310. Compaction of each layer of base or subbase material that exceeds 40 percent retained on the ¾ inch sieve shall continue until a density of not less than 98% of the maximum density has been achieved for the full width and depth of the layer. Density tests and the maximum density determined by a field proctor shall be performed by the Department. The surface, compaction and stability, shall be satisfactorily maintained until the pavement course has been placed. If required, additional water and fine material shall be applied to prevent checking, raveling or rutting. If the top of any layer becomes contaminated by degradation of the aggregate or addition of foreign material, the contaminated material shall be removed and replaced with the specified material. 3-3 All layers of base and subbase course shall be compacted to th e required density immediately after placing. As soon as the compaction of any layer has been completed, the next layer shall be placed unless otherwise authorized. The Contractor shall bear full responsibility for and make all necessary repairs to the subbase course and the subgrade until the full depth of the subbase course is placed and compacted. Repairs shall be considered incidental to other contract items. The top of any base or subbase course layer shall be scarified and loosened for a minimum depth of 1 inch immediately prior to the placing of the next layer of aggregate base or subbase. This scarifying shall be considered incidental to placing the course, and no separate payment will be made. The surface of each layer shall be maintained during compactio n operations in such a manner that a uniform texture is produced and the aggregate firmly keyed. The moisture content of the material shall be maintained at the proper percent to attain the required compaction and stability. If voids remain on the surface after the subbase course has be en constructed to grade, compacted, checked and approved, sand-leveling material shall be dumped and spread as directed. The quantity of sand leveling material shall be limited to the amount necessary to fill the voids and the minor low areas on the subbase surface. After the sand leveling material has been spread, it shall be completely rolled by a rubber-tired roller with water applied, if necessary. The surface of this material shall be maintained in its compacted and graded condition until the hot mix asphalt pavement has been placed. The furnishing, spreading, compacting and maintaining of sand leveling material will be considered included in the measurement and payment of the subbase course and no separate payment will be made. If the Contractor wishes to route public traffic over the completed Aggregate Base-Type A and B or Aggregate Subbase Course for a period of time greater than 48 hours, the Aggregate Base and Aggregate Subbase Course shall be constructed with a minimum 2″ surcharge above the design grade. Surcharge shall be constructed with material meeting the requirements of Section 703.06(b), Subbase Aggregate-Type D. Whenever the surcharge is used, it shall be placed on all the Aggregate Base and Aggregate Subbase Course subjected to public traffic. When the surcharge is removed, it may be placed in driveways, sidewalks, approach roads, or the outer portions of the shoulders. Removal of the surcharge shall be followed immediately in succession by the fine grading of the aggregate base or subbase and construction of the HMA base layer. As per subsection 203.041 Salvage of Existing Hot Mix Asphalt Pavement, Recycled Asphalt Pavement (RAP) may be used as the top 3″ of aggregate. If RAP is utilized as the top 3″, a surcharge is not required. The furnishing, placing, maintaining, and removal of the surcharge will not be paid for directly, but will be considered incidental to the Aggregate Base or Aggregate Subbase course pay item. 3-4

304.05 Surface Tolerance The completed surface of the subbase or base course shall

be shaped and maintained to a tolerance, above or below the required cross sectional shape, of ⅜ inch.

304.06 Method of Measurement Except as otherwise provided, ba se course subbase

course to the level of subgrade will be measured by the cubic yard in place unless designated by pay item to be measured by truck measure. When measured in place, the width and thickness for measurement will be the width and thickness of base or subbase as shown on the plans or as modified. The length will be along the centerline unless modified by other methods generally recognized as conforming to good engineering practice. All measurements will be in accordance with Section 108.1 - Measurement of Quantities for Payment. When designated by pay item to be measured by truck measure, the measurement will be made in vehicles at the point of delivery as shown on delivery slips in accordance with Section 108.1.3 F - Delivery Slips. As an alternative to in-place measurement, the Contractor and the Resident may agree in writing that the quantities of base or subbase for payment will be that shown in the Schedule of Items. If such an agreement is reached, no further measuring and computing of quantities will be required and the quantity referred to herein will be final. Aggregate base course and aggregate subbase course designated by pay item to be measured in place and used for driveways and other locations difficult to accurately measure in place, may be measured in vehicles at 80% of the number of cubic yards accepted and used, at the point of delivery as shown by "Delivery Slips" in accordance with Section 108.1.3 F. The quantity so measured shall not exceed 1,250 yd³ per contract, after shrinkage. Pit measured items will be measured by the cubic yard in its’ original position by ground modeling or other approved surveying methods. The final quantity will be the amount actually removed from the pit and used on the Project. Tailings, screenings, overburden, material used as other pay items, waste, and unauthorized use of the material will be deducted from the final quantity amount.

304.07 Basis of Payment The accepted quantities of base cours e and subbase course

of the type specified will be paid for at the respective contract unit price per cubic yard complete in place. When aggregate is required for slope blanket backfill, bedding under drainage structures and other foundations, it shall be paid for at twice the contract unit price for the respective aggregate base or subbase course item used. Payment for base and subbase courses shall be full compensatio n for purchasing material, stripping pits, excavating, crushing, screening, hauling, placing, compacting and other necessary processes which are required to furnish acceptable material under this item. 3-5 Water and/or fines added to material to aid compaction and sta bilization to prevent raveling and rutting shall be incidental to the work. The quantity for payment of base and subbase placed on rock su bgrade shall include only that material placed above the normal subgrade line. Furnishing and placing base and sub base backfill material between the rock and the normal subgrade line will not be paid for directly but shall be considered incidental to the work. Payment will be made under: P a y I t e m P a y U n i t

304.10 Aggregate Subbase Course-Gravel C u b i c Y a r d

304.103 Aggregate Subbase Course-Gravel, Truck Measure Cubic Yard 304.104 Aggregate Subbase Course-Gravel, Plan Quantity Cubic Yard

304.14 Aggregate Base Course - Type A Cubic Yard

304.15 Aggregate Base Course - Type B Cubic Yard

304.16 Aggregate Base Course - Type C Cubic Yard

Aggregate Base and Subbase Course in other states

• Colorado 304 · Aggregate Base Course
• Missouri 304 · Aggregate Base Course
• New Hampshire 304 · AGGREGATE BASE COURSE