1、Standard Practice for Asphalt Tack Coat Design AASHTO Designation: PP 93-181Technical Section: 2a, Emulsified Asphalt Release: Group 3 (August) American Association of State Highway and Transportation Officials 444 North Capitol Street N.W., Suite 249 Washington, D.C. 20001 TS-2a PP 93-1 AASHTO Stan
2、dard Specification for Asphalt Tack Coat Design AASHTO Designation: PP 93-18 Technical Section: 2a, Emulsified Asphalt Release: Group 3 (August) 1. SCOPE 1.1. This standard determines an application rate for emulsified asphalt or performance-graded (PG) asphalt binder for tack coats. 1.2. A tack coa
3、t is the application of an emulsified asphalt or performance-graded (PG) asphalt binder, to an existing pavement surface just prior to placement of a pavement overlay course. The tack coat is used to ensure a good bond between an existing asphalt or concrete pavement and a pavement overlay course, b
4、etween multiple pavement lifts of a structural pavement, and at any vertical surfaces to which a new pavement layer will be placed adjacent, such as curbs, gutters, utilities, and construction joints. 2. REFERENCED STANDARDS 2.1. AASHTO Standards: M 320, Performance-Graded Asphalt Binder M 332, Perf
5、ormance-Graded Asphalt Binders Using Multiple Stress Creep Recovery (MSCR) Test MP 36, Materials for Asphalt Tack Coats 3. SIGNIFICANCE AND USE 3.1. This standard may be used to select the residual asphalt application quantity of the asphalt material required for the construction of an asphalt tack
6、coat. Consult with the asphalt tack coat material supplier for their recommended application temperatures, material cure time to reduce material tracking, and unique handling requirements of their product type or grade. Note 1Many agencies use “special purpose” tack applications that yield much high
7、er bond strengths, reduce tracking, and allow tack coat materials to be applied at much higher rates. Examples include hot-applied materials, non-tracking tack coats, and tack coats applied through a spray paver. These applications may be proprietary and should be specified through local agency stan
8、dards. 3.2. Tack coats are applied to a number of different pavement surface types (Table 1). The application rate for a PG binder will be equivalent to the residual asphalt rate. Materials specifications for tack coats can be found in MP 36. 3.2.1. When using slow-setting emulsified asphalt, dilute
9、 by adding one part additional water (1:1), unless otherwise specified by the purchasing agency. Dilution involves the controlled addition of 2018 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.TS-2a PP 93-
10、2 AASHTO water or a compatible surfactant solution to the manufactured emulsified asphalt before application. Control of dilution is essential for calculating residual asphalt, as well as for achieving ultimate bond strength. It is suggested that dilution occur at the emulsion terminal and not in th
11、e field, which would allow for greater control and ability to properly verify dilution ratios. 3.2.2. Do not dilute rapid-setting or quick-setting emulsified asphalt for tack coat applications, unless otherwise specified by the purchasing agency. Provide a final product that is a fluid and homogeneo
12、us material that does not plug distributor nozzles. Note 2Ensure that emulsified asphalt residual application rates on the roadway are still satisfied after dilution. 3.3. Apply tack coats to existing paved surfaces, including new or existing asphalt mixtures, milled surfaces, portland cement concre
13、te, cold- or hot-in-place recycled mixtures, and vertical surfaces to which a new layer will be placed adjacent, such as curbs, gutters, and construction joints. The material application rates will vary with the type and condition of the existing pavement course to which the tack coat material is ap
14、plied. 4. ASPHALT TACK COAT DESIGN REQUIREMENTS 4.1. Material Quantities: 4.1.1. The tack coat application rate varies with the condition of the existing surface to which it is applied. In general, a tight or dense surface requires less tack coat than an open-textured, raveled, or milled surface. An
15、 existing flushed or bleeding surface or a new surface requires less tack coat than an existing dry or aged surface. The proper application rate also varies with the type of tack coat material used and the asphalt mixture that will be placed as an overlay. Overlays of dense-graded mixtures and gap-g
16、raded mixtures, including Stone Matrix Asphalt (SMA), require less tack coat than overlays of open-graded friction course (OGFC) mixtures. Because emulsified asphalt contains water, the tack coat application rate used by contractors is higher in order to achieve the minimum residual asphalt rate. Me
17、asurement and payment for emulsified asphalt used as tack coat are based on volume or weight (residual asphalt and water). Therefore, the estimated quantity of tack coat needed should be based on the residual asphalt rate to help eliminate confusion about dilution. 4.1.2. Design a tack coat by selec
18、ting a tack coat material in accordance with Table 2 unless otherwise required by the purchasing agency. When emulsified asphalt is selected as the tack coat material, select a specific type of emulsified asphalt (e.g., CSS-1) meeting the requirements of MP 36 unless otherwise specified by the purch
19、asing agency. When performance-graded asphalt binder is selected as the tack coat material, select a specific grade of performance-graded asphalt binder (e.g., PG 64-22 or PG 64E-22) meeting the requirements of M 320 or M 332 unless otherwise specified by the purchasing agency. When a Special Purpos
20、e material is selected as the Tack Coat material, select the specific type or grade of Special Purpose material meeting the requirements as specified by the purchasing agency. 4.1.3. Design residual asphalt and application rates for emulsified asphalt material are to conform to the residual asphalt
21、rates and the emulsified asphalt application rates shown in Table 1 unless otherwise specified by the purchasing agency. Design application rates for PG asphalt binder material are to conform to the residual asphalt rates shown in Table 1 unless otherwise specified by the purchasing agency. Design a
22、pplication rates for Special Purpose material are to conform to the residual rate and the application rate, if applicable, as specified by the purchasing agency. 2018 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applica
23、ble law.TS-2a PP 93-3 AASHTO Table 1Residual, Undiluted, and Diluted Application Rates for Tack Coat Materials Existing Surface Type Residual Asphalt Rate, gal/yd2Emulsified Asphalt Application Rate Undiluted,agal/yd2Emulsified Asphalt Application Rate Diluted 1:1,agal/yd2New Asphalt Mixture 0.0200.
24、045 0.0330.075 0.0660.150 Existing Asphalt Mixture 0.0400.070 0.0670.117 0.1330.234 Milled Surfaces 0.0400.080 0.0670.133 0.1330.266 Portland Cement Concrete 0.0300.050 0.0500.083 0.1000.166 aAssumed slow-setting emulsified asphalt at 43 percent water and 57 percent asphalt. Table 2Tack Coat Materia
25、l for Project Type/Time Project Type/Time Recommended Tack Coat Material Standard (Traffic volume 5,000 ADT) PG Asphalt Binder or Special PurposeaNighttime Paving with Short Time Windows (8 hours) PG Asphalt Binder, Special PurposeaaSee Section 3, Note 1. 5. REPORT 5.1. Report the selected specific
26、type of emulsified asphalt, specific grade of performance-graded asphalt binder, or specific type or grade of Special Purpose material (e.g., CRS-1, PG 64-22, or Special Purpose Type/Grade XXX). 5.2. Report the emulsified asphalt or hot PG asphalt binder spray application rate in gallons per square
27、yard to the nearest 0.001 gal/yd2. 5.3. Report the designed residual asphalt rate to the nearest 0.001 gal/yd2. 6. KEYWORDS 6.1. Emulsified asphalt; performance-graded asphalt binder; tack coat. APPENDIX (Nonmandatory Information) X1. METHOD TO CONVERT RESIDUAL BINDER RATES TO EMULSIFIED ASPHALT RAT
28、ES BASED ON EMULSIFIED ASPHALT CONTENTS AND DILUTION RATES X1.1. Calculating emulsified asphalt application rates needs to account for not only the water that is present in the original emulsified asphalt, but also any added water via dilution. 2018 by the American Association of State Highway and T
29、ransportation Officials. All rights reserved. Duplication is a violation of applicable law.TS-2a PP 93-4 AASHTO X1.2. Example Calculations: Assume a tack coat designed residual asphalt application rate of 0.050 gal/yd2. 1. What should be the application rate for undiluted CRS-1 emulsified asphalt? C
30、RS-1 is 60 percent residual asphalt: 220.050 gal residual asphalt rate 1 gal CRS-1 0.083 gal CRS-10.60 gal residual asphaltyd yd= 2. What should be the application rate for CRS-1 emulsified asphalt diluted 1:1 with water? CRS-1 is 60 percent residual asphalt: 0.050 gal residual asphalt rate 1 gal CRS-1 2 gal Diluted CRS-1 0.175 gal Diluted CRS-10.57 gal residual asphalt 1 gal CRS-1yd yd = 2018 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.
