311.1-DESCRIPTION: This work shall consist of constructing a base course of coarse stabilized aggregate spread and compacted on a prepared surface in accordance with these specifications and in re asonably close conformance with the lines, grades, thickness, and typical cross sections as shown on the Plans or as established by the Engineer. It is the intent to allow the Contractor a choice between asphalt stabilizer and Portland cement stabilizer. 311.2-MATERIALS: Depending on the alternative chosen, (asphalt or Portland cement) the materials shall conform to the requirements of the following subsections of Division 700. MATERIAL SUBSECTION UNIT Aggregate* 703.1, 703.2, 703.3, 703.4 AASHTO 57, 67, 357, or 467 Curing Material*** 707.10 Performance Graded Binders** 705.5 Standard grade for area Portland cement*** 701.1 Type 1 Water*** 715.7 * If river gravel is used, the crushed particle requirement shall be 100% two face fracture. ** Asphalt stabilized applications only. *** Portland cement applications only. CONSTRUCTION METHODS 311.3-GENERAL: General requirements shall comply with the applicable portion of 401.3 of the Specifications. 311.4-COMPOSITION OF OPTIONAL STABILIZING MIXTURES: If the asphalt stabilized alternative is used, the asphalt cement shall be confined to 2.0%, plus or minus 0.5% by weight of the mix if Blast Furnace Slag is used the asphalt cement may be increased. If the Portland cement stabilized alternative is chosen, the cement shall be Type 1 and shall have a minimum cement content of 150 ± 5 pounds per cubic yard. This base course shall be capable of withstanding construction operations without showing any detrimental effects. 311.5-TESTING: 311.5.1-Quality Control Testing: Quality control is the responsibility of the Contractor as specified in subsection 106.1. The contractor shall design a quality control plan detailing the methods by which the quality program will be conducted. The Contractor shall conduct one test daily to determine mix properties in accordance with subsection 311.4. Frequency will be one test per day. Acceptance for gradation will be in accordance with section 703.4. If gravel is used for the coarse aggregate a crushed particle analysis, in accordance with Section 311.2 will be conducted before placement and every 10,000 -ton thereafter. Unless otherwise specified compaction testing shall be waived. 311.5.2-Acceptance Testing: Acceptance sampling and testing of aggregates is the responsibility of the Division, except for furnishing the necessary materials. The Division may use quality control sampling and testing performed by the Contractor for Acceptance. 311.6-WEATHER AND SEASONAL LIMITATIONS: Weather and seasonal limitations shall be in accordance with 401.8 for asphalt applications. Portland cement base shall not be mixed or placed while the temperature of the course on which the material is to be placed is below 40°F. When conditions indicate that the temperature of the in-place material may fall to less than 35° F within 24 hours, adequate means satisfactory to the Engineer shall be provided for the protection of the work. In no instance shall the mix be placed on frozen subgrade. 311.7-EQUIPMENT: Depending on the alternative used, equipment shall meet the applicable requirements of subsection 401.9 or 501.5 – whichever is appropriate. 311.8-PREPARATION AND BATCHING OF MATERIALS: All aggregate shall be dried until it has no surface moisture and not more than 0.5 percent (0.5%) of absorbed moisture. Mixing temperature of aggregate shall be as directed and shall range between 225° - 300°F. Asphalt material shall be heated in melting kettles or tanks designed to secure even heating of the mass. Heating temperatures shall be as directed and shall range between 250° - 275°F. The temperature of the mix shall be within the range of 200° - 250°F. Preparation of materials for Portland cement applications shall conform to the requirements of 501.7. 311.9-MIXING AND TRANSPORTING REQUIREMENTS: The materials used in asphaltic mixes shall be mixed in an asphalt concrete mixing plant that has been inspected and approved by the Division. Transportation of su ch mixes shall be in accordance with 401.09.7 of the Specifications. The materials used in Portland cement mixes may be mixed at a central mix plant, in a transit mix truck or a pugmill type mixer. Regardless of which type of equipment is used, the mixing time shall be a minimum of two minutes once all component materials are batched.
311.10 Placing, Spreading, and/Or Compacting:
Placement of the stabilized material shall be by acceptable spreading equipment to the appropriate line, grade and thickness. Acceptable equipment includes aspha lt pavers for asphalt stabilized bases and spreader boxes, self-propelled spreaders or conventional concrete placing equipment for Portland cement stabilized bases. A four to ten ton steel wheel tandem roller shall be used to compact the asphalt stabilize d free draining base material. The number of roller passes shall be two or three unless otherwise directed. In the case of the asphalt stabilized aggregate, the mat temperature, at the time of initial rolling, shall be between 150 and 175F unless other wise directed. In the case of the asphalt stabilized aggregate, the purpose of the rolling is to compact the base sufficiently to support the weight of the equipment that will place the next layer or pavement. The compacted base is to be porous so that water will drain through it. The base is not to be compacted to the point that it is not free draining or that the aggregate is crushed.
311.11 Curing:
No curing is required for Portland cement stabilized based.
311.12 Tolerance:
Thickness tolerance shall meet the requirements of 307.6.2.
311.13 Maintenance:
The Contractor shall maintain the base course porous and free from being contaminated or clogged by deleterious material, transported and deposited by construction equipment, traffic, etc., until the next layer of the pavement is placed. The Contractor shall also maintain the final surface of the base course true to specified line, grade and cross section until such time that the pavement is placed.
311.14 Method of Measurement:
The quantity of work done will be the number of cubic yards measured in place. Any additional work beyond the scope of the original plans but authorized by the Engineer will be measured in place and paid at the unit bid price, subject to the provisions of 104.2 and 109.2. Base course constructed outside the lines, dimensions and cross sections shown on the Plans or designated will not be measured for payment.
311.15 Basis of Payment:
The quantity, determined as provided above, will be paid for at the contract unit price bid for the item below, which price and payment shall constitute full compensation for furnishing all the materials and doing all the work prescribed in a workmanlike and acceptable manner, including labor, tools, equipment, supplies, and incidentals necessary to complete the work.
311.16 Pay Item:
ITEM DESCRIPTION UNIT 311006-* Open Graded Free Draining Base Course Cubic Yard * Sequence number
Division 400
ASPHALT PAVEMENTS
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