602 - HOT MIX ASPHALT (HMA) CONSTRUCTION (Quality Control/Quality Assurance (QC/QA))
600-9 Table 602-6: Mix Design Test Data Submittals
Submittal Information Minimum of 2 Mix Designs As a minimum, 1 mix design at the P br and 1 mix design at 0.3% to 0.5% below the Pbr Gmm Determined at each binder content. Individual and Bulk Specific Gravity Tests Provide results for a minimum of 2 specimens at each binder content. Percent Air Voids Provide % Va in the mixture for each binder content when compacted to N ini, N des and N max gyratory revolutions along with copies of the Gyratory graphs. Percent VMA Provide %VMA at each binder content. (Note: The Contractor is cautioned that plant produced material generally yields a mixture with less VMA than predicted by the design. In such case, the design VM A should be increased above the specified minimum accordingly.) D/B Ratio Calculate to the nearest 0.1% at each binder content.
f.Additives. Provide Warm Mix Asphalt (WMA) add itives or processes that comply with SECTION 1203 . The Contractor is permitted to use WMA, unless otherwise shown in the Contract Documents. For mixes containing Warm Mix Asphalt (WMA) ad ditives, submit for the Engineer’s review and approval, the additive or process used, the recommended rate of application, and the temperature ranges for mixing and compaction. Mixing temperature range is provided by the Asphalt Binder Supplier. When using WMA, the mixing temperature may be reduced no more than 30oF for WMA water foaming processes, and no more than 70oF for WMA chemical and organic additives. The minimum mixing temperature for WMA is 220oF. 602.4 CONSTRUCTION REQUIREMENTS
a.Plant Operation. Adjust all plant operations to operate continuously.
1.Preparation of the Asphalt Bi nder. Heat the asphalt binder to within a range as specified in SECTION 601. When heating the asphalt binder to the specified temperat ure, avoid local overheating. At all times, provide a continuous supply of the as phalt binder to the mixer at a uniform temp erature. Asphalt binder received from the refinery at temperatures less than 37 5°F may be used as received, if the requirements regardin g the reheating of asphalt binder in SECTION 601 are met.
a.Commingling of Asphalt Binders. Do not a dd or commingle asphalt binders from 2 or more sources into a storage tank. If this occurs, th e contents of the storage tank are considered contaminated. Do not use the contents of the st orage tank on the project, except as follows: It is permissible, at the Contractor’s option, to thoroughly mix the contents of the tank and request sampling of the mixture. Submit the sample to the MRC for testing. Do not use the asphalt binder until approved, and when needed, a new mix design evaluation is completed. (b) Asphalt Binder Sources. Before changing as phalt binder sources on a project, obtain approval from the DME. A new JMF may be required.
c.Anti-Strip Additives. If liquid anti-strip additives are added at the Contractor’s plant, install a “totalizer” to monitor the quantity of anti-strip additive being added. The Engineer may approve alternative methods for including anti- strip additives in a batch plant. If added at the plant, the anti- strip will be added in line with the asphalt binder as it is being transferred from the transit unit to the asphalt binder storage tank. Provide a method for the Engineer to monitor the percent of additive being added. If hydrated lime is added, mix it in an approved pug mill to coat the combined aggregates. Moisten the combined virgin aggregate to a minimum of 3% above the saturated surface dry condition prior to, or during the addition of the hydrated lime.
d.WMA Additives. If WMA additives are added at the Contractor’s plant, install a “totalizer” to monitor the quantity of WMA additive being added. The Engineer may approve alternative methods for including chemic al and organic WMA additives in a batch plant. If added at the plant, chemical and organic WMA additives will be added in line with the asphalt binder as it is being transferred from the transit unit to the asphalt binder storage tank. Provide a method for the Engineer to monitor the percent of additive being added. 602 - HOT MIX ASPHALT (HMA) CONSTRUCTION (Quality Control/Quality Assurance (QC/QA))
600-10 (2) Preparation of Mineral Aggregate. When the mineral aggregate is composed of 2 or more ingredients,
combine as shown in the approved JMF.
a.Temperature Requirements. Dry the aggregate fo r the mixture and heat to a temperature to obtain an asphalt-aggregate mixture temperature immediately after mixing within the 75 to 150 second Saybolt viscosity range of the aspha lt binder used. Obtain the temperature for this viscosity range from the MRC or the Asphalt Binder Producer. No mixing or compaction temperatures are to exceed 340ºF without approval from the Field Mate rials Engineer. The minimum temperature may be revised by the DME provided it is demonstrated that satisfactory results may be obtained at a lower temperature. In such event, deliver the HMA to the paver at a temperature sufficient to allow the material to be satisfactorily placed and comp acted to the specified density and surface tolerance requirements.
3.Preparation of HMA. Introduce asphalt binder into the prepared aggregate in the proportionate amount determined by the P br in the JMF.
a.Basis of Rejection. HMA will be rejected if th e aggregate, as it is discharged from the drum or the pugmill, contains sufficient moisture to cause foaming of the mixture, or if the temperature of the aggregate is such that the as phalt-aggregate mixture temperatur e is outside the range specified in SECTION 601 .
b.Mixing Time. Operate drum mixers at a rate to provide uniform aggregate coating in a continuous operation. For batch and continuous ty pe plants, the minimum wet mixing time is 40 seconds. In all cases, mix a sufficient time to produce a uniform mixture in which all the aggregate particles are thoroughly coated. On batch plants, begin the timing at the start of the asphalt binder introduction into the pugmill, and end upon the opening of the discharge gate. For continuous flow plants, mixing time in seconds shall equal: [pugmill dead capacity in pounds] divide d by [pugmill output in pounds per second].
c.Manufacturer’s Specifications. Operate all drying, pumping and mixing equipment within the limits specified by the manufacturer, unless it can be demonstrated to the satisfaction of the Engineer that such limits may be exceeded without detriment to the HMA. (d) Batcher Operation. Coordinate HMA batchers (Gob Hoppers) with the plant production rate at all times so the hopper is more than ¾ full before the gates open, and the gates close before material can drop through the gob hopper directly into the surge bin, weigh hopper or truck. (e) Wasted Material. Wasted mate rial is not measured for pay. If after an interruption of production, the drum-mixer contains cold, uncoated or otherwise unsuitable material, waste material through a diversion chute. In a continuous or batch plant drier, waste unsuitable material through the pugmill. At the end of a production run, waste any segregated material in the cone of the storage bin.
4.End of Day Quantities. At the end of each day of production provide the E ngineer with a document signed by the Plant Foreman or the Project Manager listing the dry weight of each aggreg ate, mineral filler, RAP, and WMA chemical or organic additive; the tons of asphalt binder, the tons of anti-strip agent used for the project during the day, and the tons of water used in the WMA foaming process. The dry weight is the tons of the material less the water content.
b.Road Surface Preparation.
1.Preparation of Earth Su bgrade. When the HMA is placed on a prepared subgrade, and unless other subgrade preparation is called for in the Co ntract Documents, perform the following: At all grade control points, such as existing pavements and bridges, excavate the subgrade according to the specified grades and lines, prior to any subgrade treatment. Prior to the delivery of materials for the base course, prepare the subgrade surface by sprinkling with water, lightly scarifying wh ere necessary, and blad ing and rolling, until the proper crown is obtained. Disturb the originally compacted crust or top portion of the subgrade as little as possible. Maintain the subgrade as pr epared until it is covered with the base course. Repair any defects which may develop, at the Contractor’s expense, to the satisfaction of the Engineer. (2) Trimming of Subgrade (Untreated, Treated or Modi fied), Aggregate Base or Granular Sub-base for HMA Pavement. Before placing the subsequent layer of the pavement structure, trim the subgrade (untreated, treated or modified), aggregate base or granular subbase. Use an auto mated, electronically controlled machine that trims with a rotary cross-shaft trimmer to establish and control the line, grade and typical cross-section as shown in the Contract Documents. The Engineer may waive the use of automatically controlled equipment on areas of narrow width or
Source: Kansas Standard Specifications for State Road and Bridge Construction, 2015 Edition. Pages 246–247 of 978.