2357Bituminous Tack Coat

2357.1DESCRIPTION

This Work consists of applying bituminous Material (emulsion or cutback asphalt) on a bituminous or concrete pavement before paving a new Lift of plant mixed Asphalt.

2357.2MATERIALS

The Bituminous Material for tack coat will be limited to one of the following kinds of emulsified asphalt. Use of medium cure cutback asphalt (MC-250) is allowed during the early and late construction season when it is anticipated the air temperature may drop below 32 degrees Fahrenheit. Allowable grades are as follows: Emulsified Asphalt AASHTO M 208 Standard Specification for Cationic Emulsified Asphalt, dilution of the emulsion is only allowed by the supplier. No field dilution is allowed. The storage tank for diluted emulsion must have a recirculation system or agitator that will prevent settlement or separation of the Material . Table 2357.2-1 Residual Asphalt Content Minimum Residual Asphalt Content Emulsion Undiluted Diluted (7:3), D30 Diluted (8.5:1.5), D15 CSS-1 or CSS-1h 57 percent 40 percent N/A CQS-1h N/A N/A 53 percent Cutback Asphalt Medium Cure Liquid Asphalt MC- 250 Use only sources listed on the APL, Asphalt Products.

2357.3CONSTRUCTION REQUIREMENTS

A Restrictions Conduct tack coat operations in a manner that offers the least inconvenience to traffic. Maintain movement in at least one direction at all times without pickup or tracking of the bituminous Material. Do not apply the tack coat when the Road surface or weather conditions are unsuitable as determined by the Engineer. Limit the daily application of tack coat to approximately the area on which construction of the subsequent bituminous course can reasonably be expected to be completed that day. B Equipment B.1 Distributor ................................................................................................... 2360.3B.2.d C Road Surface Preparations Remove all foreign matter on the Road surface before applying tack coat and dispose of as approved by the Engineer. Apply the bituminous tack coat Material to a dry and clean Roadway surface. All necessary repairs or reconditioning must have been completed as provided for in the Contract and approved by the Engineer.

D Application of Bituminous Tack Coat Material Unless otherwise indicated in the Plans or Special Provisions, apply the bituminous tack coat Material within the application rates shown below in Table 2357.3-1, as based on pavement type or condition and type of bituminous Material. Dilution of asphalt emulsion in the field is not allowed. Before placing an abutting bituminous course, provide a uniform coating of liquid asphalt or emulsified asphalt to the contact surfaces of all fixed Structures and at the edge of the in-place mixture in all courses at transverse joints and in the final wearing course at longitudinal joints . All tack coat must break and turn from brown to black, before paving the subsequent Lift or course. Do not allow vehicles to drive on tack coat that has not broken. Apply a uniform tack coat to the existing asphalt or concrete surface and to the surface of each course or Lift constructed, except for the final course or Lift. Tack each Lift when placing multiple Lifts in the same day. Uniform application will not have streaks (corn rows), bare spots, puddles, or other irregular patterns. The Engineer will compare the freshly sprayed emulsion to a brown sheet of construction paper or a black sheet of construction paper for broken tack coat to determine conformance with tack coat application uniformity. Using a distance of 1,000 feet perform a yield check at the beginning of each Project to verify the application rate is correct. The Engineer may require additional yield checks be performed if the application rate is questioned. The Engineer may also require the Contractor to verify application is within 10 percent of the intended application rate by ASTM D2995, Standard Practice for Estimating Application Rate and Residual Application Rate of Bituminous Distributors, test method A. Table 2357.3-1 Tack Coat Application Rates Application Rates – gallon/square yard Material Type CSS-1 or CSS-1h CSS-1 or CSS-1h CQS-1h MC║ Surface Type Undiluted Emulsion Diluted* Emulsion (7:3), D30 Diluted* Emulsion (8.5:1.5), D15 Cutback New Asphalt 0.04 to 0.06 0.06 to 0.09 0.05 to 0.07 0.05 to 0.07 Old Asphalt† and PCC 0.05 to 0.09 0.07 to 0.135 0.08 to 0.10 0.09 to 0.11 Milled Asphalt and Milled PCC 0.06 to 0.09 0.09 to 0.135 0.09 to 0.11 0.09 to 0.11 Notes: * As provided by the asphalt emulsion supplier (see 2357.2A, “Bituminous Material”) ║Use when approved by the Engineer † Older than 1 year E Bituminous Temperature The application temperature of the bituminous Material will be:

F Bituminous Sampling Sample asphalt emulsion from either the spigot or a nozzle on the distributor according to the Schedule of Materials Control.

G Pedestrian Crossings Spread sand on newly tacked surfaces at regularly utilized and open for public use pedestrian crossings. H Acceptance of Tack Material The Engineer will address failures related to 3151, “Bituminous Material,” in accordance with 2357.5A, “Monetary Adjustments.” Deficiencies related to workmanship or application will be addressed in accordance with 1512, “Unacceptable and Unauthorized Work.”

2357.4METHOD OF MEASUREMENT

Bituminous Material used for tack coat will be measured by volume at 60°F.

2357.5BASIS OF PAYMENT

Payment for the accepted quantity of asphalt emulsion and cutback shall be at the Contract P rice per unit of measure. The cost of providing and applying sand at pedestrian crossings is included in the 2360, “Plant Mixed Asphalt Pavement,” bid item. If the Contract does not contain a Pay Item for Bituminous Material for tack Coat, the cost is included in the 2360, “Plant Mixed Asphalt Pavement,” bid item. A Monetary Adjustments The Department must apply Incentives and Disincentives and may apply monetary deductions for Bituminous Tack Coat. The amounts of these adjustments are deemed reasonable. The Engineer in conjunction with the Bituminous Engineer may deduct up to 5 percent of the mixture Unit Price for failures related to 3151, “Bituminous Material.” B Schedule Payment for the tack coat will be made on the basis of the following schedule: Item No. Item Unit

2357.506 Bituminous Material for Tack Coat gallon