460ASPHALT TACK COAT

460.1DESCRIPTION—This work is the conditioning and treating of an existing surface with an application

of emulsified asphalt bonding material.

460.2MATERIAL

of Compliance as specified in Section 106.03(b)3 and a Bill of Lading as specified in Section 702.1(c) to the Representative indicating the asphalt residue content (ARC) of the material being used. If the emulsified asphalt material is stored for 30 days or longer after certification, resample and retest the emulsified asphalt material at no additional cost to the Department to determine if it meets Bulletin 25 specification requirements.

TABLE A Emulsified Asphalt Materials Class of Material Type of Material Application Temperature F Minimum Maximum TACK Anionic or Cationic Emulsified Asphalt 90 150 NTT/CNTT Anionic or Cationic Emulsified Asphalt 140 180

460.3CONSTRUCTION—

maintained, and operated to apply material uniformly on surfaces with varying widths and up to 15 feet wide. Provide a distributor capable of maintaining a uniform distributing pressure and controlling the application rate

gauges, accurate volume-measuring devices or a calibrated tank, a thermometer for measuring temperatures of tank contents, a power-operated pump, and full circulation spray bars with lateral and vertical adjustments. Provide nozzles sized according to the manufacturer’s recommendations for the material selected for application. In the field, determine the distributor’s application rate according to PTM No. 747. The Contractor may use hand-spraying equipment in areas inaccessible to the distributor. Apply tack coat at an application rate, approved by the Representative, to leave a uniform asphalt residual rate within the ranges per surface type according to Table B. Identify the application rates and the residual rates on the Paving Operation QC Plan and review the QC plan application rates and residual rates with the Representative at the Preplacement Meeting.

TABLE B Uniform Asphalt Residual Rates by Surface Type Surface Type Uniform Asphalt Residual Rates (RR) (gallons per square yard) New Asphalt Paving 0.03 to 0.05 Existing Asphalt Paving 0.04 to 0.07 Milled Surface (Asphalt & Portland cement concrete) 0.04 to 0.08 Portland cement concrete 0.04 to 0.07

The application rate to achieve a uniform asphalt residual rate can be determined using the following equation:

AR = (RR / ARC)

AR = Application Rate, (gallons per square yard); the amount of emulsified asphalt sprayed by the distributor truck.

RR = Residual Rate; (gallons per square yard); the amount of emulsified asphalt remaining on the surface after it has broken and set.

ARC = Asphalt Residue Content; (% divided by 100); the percentage amount of asphalt in the emulsified asphalt. Provided on the Bill of Lading and expressed as a decimal.

When paving operations begin, apply tack coat on a 100-linear foot minimum test section on the project for each paving course. Apply tack coat at the distributor’s application rate to achieve the proposed residual rate within the ranges listed in Table B. Adjust distributor application rate and spray bar height to obtain a uniform surface coverage. Review adequacy of the tack coat coverage with the Representative before continuing with the tack coat application. Apply the tack coat only when the air temperature is 40F and rising and when the existing surface is dry. Before each paving course, apply the tack coat at an application rate to be within ranges of the uniform asphalt residual rate for the surface type according to Table B. Uniformly distribute the tack coat over the entire surface. Extend the tack coat a minimum of 6 inches beyond the longitudinal joint of the paving course being placed. Correct all uncoated or lightly coated areas as directed to the Representative’s satisfaction. At designated locations, correct areas with an excess of emulsified asphalt material by covering the area with sufficient dry fine aggregate to blot up or remove excess tack coat. Allow the tack coat to break and set, without being disturbed. Do not begin paving until the Representative determines the tack coat has cured to the point that tracking is minimized.

damaged areas to the Representative’s satisfaction before placing the next pavement course.

460.4MEASUREMENT AND PAYMENT—