114 ALASKA 2020 SECTION 306 ASPHALT TREATED BASE COURSE
306-1.01 DESCRIPTION . Construct a plant -mixed asphalt treated base (ATB) course on an
approved foundation to the lines, gr ades, and depths shown on the Plans.
306-2.01 MATERIALS. Use materials that conform to the following:
Aggregate Subsection 703- 2.03, grading D -1, except change the minimum Degradation Value to 30. Asphalt Section 702, for the type and grade shown on the bid schedule. Use PG
52-28 if no Grade is specified.
Anti-Strip As required by the approved Job Mix Design. CONSTRUCTION REQUIREMENTS
306-3.01 COMPOSITION OF MIXES. At least 15 days in advance of the production of ATB,
submit a representative 300- pound sample of the aggregate proposed for the project. Also submit a representative 3- gallon sample of the asphalt binder and a one- pint sample of the anti -strip additive proposed for use in the mix. From this information the Engineer will establish the Job Mix Design, including the maximum specific gravity (MSG). The MSG will be determined by ATM 209. When changes in the aggregate gradation or aggregate source occur, submit representative samples, in the same manner as above, for a new mix design. Use anti -strip a gents in the proportions determined by ATM 414 and included in the approved Job Mix Design. At least 70 percent of the aggregate must remain coated when tested under ATM 414.
306-3.02 WEATHER LIM ITATIONS. Do not place the asphalt mixture on a wet or frozen surface,
or when weather conditions will prevent proper handling, compacting or finishing of the mixture. Do not place the asphalt mixture unless the air temperature is above 40 °F, as measured in the shade and away from any heat sources.
306-3.03 STOCKP ILING. Aggregates may be stored in a single stockpile. Minimize segregation
and contamination.
306-3.04 Equipment.
1.Mixing Plant . Conform to Subsection 401- 3.05.
2.Hauling Equipment . Conform to Subsection 401- 3.06.
3.Spreading Equipment . Use either a self -propelled paving machine conforming to Subsection
401-3.07 or motor grader.
4.Rollers . Conform to Subsection 401- 3.08.
306-3.05 PREPARATION OF ASPHALT. Provide a continuous supply of asphalt binder to the
mixer at a uniform temperature, within the allowable m ixing temperature range.
306-3.06 PREPARATION OF AGGREGATE. Heat and dry the aggregate for the mix to within
±25 °F of the Mix Design temperature. Adjust dryer flames to avoid damage to aggregate and to avoid soot on the aggregate.
306-3.07 MIXING. Mix AT B materials per Subsection 401- 3.10. Aggregates will be accepted
based on samples taken from the combined aggregate cold feed conveyor during ATB production. 115 ALASKA 2020 306-3.08 SPREADING A ND FINISHING. Deposit and spread ATB mixture on an approved surface in layers not exceeding 3 inches in compacted depth. On areas where irregularities or unavoidable obstacles preclude spreading by mechanical equipment, deposit the mixture in layers, spread, rake, and lute using hand tools. The depth of such layers is governed by t he ability of the compaction equipment to achieve the required degree of compaction. Place a tack coat between successive layers of base material. When successive layers are placed on the same day, or have not been contaminated by sand or dust or not subject to traffic, the tack coat may be deleted.
306-3.09 COMPACTION. Use vibratory rollers, steel -wheeled tandem rollers and/or pneumatic
tired rollers for initial rolling. Use steel -wheeled tandem rollers for final rolling. Compact each layer to a minimum density of 94 percent of the MSG. Acceptance densities will be determined by ATM 410. Cut full depth core samples from the finished mat within 24 hours after final rolling. Neatly cut the samples with a minimum diameter of 6 inches with a core drill at the randomly selected location designated by the Engineer. Backfill and compact all voids left by coring with new asphalt concrete mixture within 24 hours.
306-3.10 SURFACE TES T. After rolling has been completed, the surface will be tested for
smoothness and accuracy of grade, crown, superelevation, and width. Limit surface deviations to 3/8 inch, as measured from the testing edge of a 10- foot straightedge between two contacts with the surface parallel with, and at right angles to, the centerline.
306-3.11 TH ICKNESS REQUIREMENTS . Meet Plan thickness ± 1/2 inch, compacted.
306-4.01 Method of M Easurement.
1.ATB. See Section 109. No deduction will be made for the weight of asphalt binder or anti -strip additive in the mixture.
2.Asphalt Binder . Subsection 401- 4.01, ex cept that no payment will be made for asphalt binder in excess of the upper specification limit.
3.Anti-Strip Additive . Based on the number of tons of asphalt binder containing required additive.
306-5.01 Basis of Pa Yment.
Anti-Strip Additive . At the unit p rice specified in the Special Provisions or Directive. If no pay item is included for anti -strip additive, it is subsidiary. Payment will be made under: PAY ITEM Item Number Item Description Unit 306.0001.____ ATB TON 306.0002.____ Asphalt Binder, Gra de ___ TON 306.0003.____ Anti-Strip Additive CS 116 ALASKA 2020 SECTION 307 EMULSIFIED ASPHALT T REATED BASE COURSE
307-1.01 DESCRIPTION . Construct an emulsified asphalt treated base (EATB) course on a
prepared foundation to the lines, grades, and depths shown on the Plans.
307-2.01 MATERIALS. Use materials that conform to the following:
Aggregate Subsection 703- 2.03 Asphalt Section 702, for the type and grade shown on the bid schedule Use PG 52 -28 if no Grade is specified Anti-Strip As required by the approved Job Mix Design Portland Cement Section 701 (Type I)
307-2.02 COMPOSITION OF MIXES. At least 15 days in advance of the production of EATB
material, furnish a representative 300- pound sample of the base aggregate proposed for the project, and a representative 3- gallon sample of the asphalt binder, and a one- pint sample of antistrip additive if used in the mix. The Engineer will determine the job mix design. Changes in aggregate gradation or aggregate sources will require a new job mix design. Submit samples in the same manner as the original submittal. Use anti -strip agents in the proportions determined by ATM 414 and included in the approved Job Mix Design. At least 70 percent of the aggregate must remain coated when tested by ATM 414. CONSTRUCTION REQUIREMENTS
307-3.01 Mixing.
1.Mix EATB material either
a.at an approved central mixing plant,
b.in place, on an approved subgrade, or
c.on an approved mixing area. If method b. or c. above is used, prevent contamination of the base course material by the underlying material. Adjust aggregate moisture content prior to asphalt application. Apply portland cement, if required, to the aggregate immediately prior to mixing. Acceptance of aggregates will be based upon representative samples taken just prior to the addition of the emulsified asphalt.
2.Central plants may be either batch or continuous twin- shaft pugmill units equipped with adequate proportioning devices to control aggregate, asphalt, water and portland cement. Combine the aggregate, emulsified asphalt, portland cement , and water, in the mixing plant in the specified proportions. Adjust the mixing time to the minimum time which will provide a complete coating of the aggregate particles.
3.Perform in- place mixing with single or double pugmill travel plants, rotary cross -shaft mixers, or motor grader (blade). Equip travel plants and cross -shaft mixers with adequate proportioning devices to control asphalt. Use distributors for applying asphalt for in- place blade mixing which conform to Subsection 402- 3.02.
Source: Alaska Standard Specifications for Highway Construction, 2020 Edition. Pages 142–143 of 584.