1、Standard Practice for Emulsified Asphalt Fog Seal Design AASHTO Designation: PP 88-171Technical Section: 2a, Emulsified Asphalts Release: Group 3 (August 2017) American Association of State Highway and Transportation Officials 444 North Capitol Street N.W., Suite 249 Washington, D.C. 20001 TS-2a PP
2、88-1 AASHTO Standard Practice for Emulsified Asphalt Fog Seal Design AASHTO Designation: PP 88-171Technical Section: 2a, Emulsified Asphalts Release: Group 3 (August 2017) 1. SCOPE 1.1. This standard determines an ideal application rate of emulsified asphalt for use as a fog seal. 1.2. A fog seal is
3、 the light application of emulsified asphalt to the pavement surface, which may be used to provide a surface seal, arrest light raveling, or create color contrast between traffic lanes and shoulders to improve visibility. Fog seals are also applied to newly placed chip seals to lock in loose chips a
4、nd provide a more aesthetically pleasing finished product. 2. REFERENCED DOCUMENTS 2.1. AASHTO Standards: M 140, Emulsified Asphalt M 208, Cationic Emulsified Asphalt M 316, Polymer-Modified Emulsified Asphalt MP 33, Materials for Emulsified Asphalt Fog Seal T 304, Uncompacted Void Content of Fine A
5、ggregate 3. SIGNIFICANCE AND USE 3.1. This standard may be used to establish the ideal application rate, residual rate or quantity of emulsified asphalt required for the construction of emulsified asphalt fog seals. 3.2. Fog seals may be applied to a number of different pavement surface types. Commo
6、n uses include sealing dense-graded asphalt mixtures, preventing raveling on open-graded asphalt mixtures locking down aggregates on new chip seals, or sealing shoulders to improve contrast for nighttime visibility. Although slow-setting emulsified asphalts are most commonly used for fog seals, emul
7、sified asphalt type, dilution ratio, and application rate vary markedly among the common applications. Climate, traffic, and local preferences also play important roles in selecting emulsified asphalt type and grade. For details regarding materials selection, refer to MP 33. 3.3. DilutionEmulsified
8、asphalts used as fog seals are typically diluted 1:1 by weight with water or a compatible surfactant solution before application. The final diluted product shall be a fluid, homogeneous mixture that does not plug distributor nozzles. The minimum residue content for emulsified asphalts used as fog se
9、al will typically be 50 percent of undiluted emulsified asphalt. Slow-setting emulsified asphalts can be diluted with water. All other emulsified asphalt types must be diluted at the manufacturers plant site using a surfactant solution compatible with the 2017 by the American Association of State Hi
10、ghway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.TS-2a PP 88-2 AASHTO emulsified asphalt. The bill of lading shall include the minimum asphalt residue percentage of the material delivered. 3.4. The rate of application may vary with the type and co
11、ndition of the surface. 4. EMULSIFIED ASPHALT FOG SEAL DESIGN REQUIREMENTS 4.1. MaterialsBefore dilution, emulsified asph alt for fog seal shall meet the requirements of M 140, M 208, and M 316 as applicable. If fine aggregate is used for friction, it shall have a minimum angularity of 45 as determi
12、ned by T 304. 4.2. Material QuantitiesEmulsified asphalt should meet the requirements in MP 33. The application rates may be determined by a test strip according to the procedure in Section 4.4, or determined empirically by the ring test detailed in Section 4.5. Emulsified asphalt samples used to op
13、timize application rate should be representative of the materials used for the project. Table 1Initial Target Fog Seal Application Rate Surface Type Residual Rate Gal/yd2Undiluted Gal/yd2Diluted 1:1aGal/yd2Dense-Graded Asphalt Mixture 0.0150.021 0.0250.035 0.050.07 Open-Graded Asphalt mixture 0.0210
14、.027 0.0350.045 0.070.09 Chip Seal (1/2in. top agg size) 0.0270.033 0.0450.055 0.090.11 Chip Seal (1/2in. top agg size) 0.0330.039 0.0550.065 0.110.13 a Assume emulsified asphalt is 40 percent water and 60 percent asphalt. 4.3. Method to convert binder content to total emulsified asphalt content bas
15、ed on residual values: 4.3.1. Calculating residual asphalt application rates needs to account for not only the water that is present in the original emulsified asphalt but also any added water added by dilution. 4.3.2. For example, if an application of 0.10 gal/yd2might be made using an SS emulsifie
16、d asphalt with a 60 percent asphalt residue content (40 percent water) which is then diluted 1:1 (original emulsified asphalt: water). Calculation of the residual application rate would need to account for both sources of water. The application rate of 0.10 gal/yd2would be multiplied by 0.50, to acc
17、ount for the dilution, and then by 0.60, to account for the water in the original emulsified asphalt. Therefore, the residual fog seal rate in this example would be 0.030 gal/yd2. 4.4. Test Strip: 4.4.1. Emulsified asphalt should be applied at an application rate of 0.05 to 0.13 gal/yd2of the dilute
18、d material. Lighter application rates are used for tight, smooth surfaces and heavier application rates for open, coarse surfaces such as a chip seal, as described in Table 1. 4.4.2. Construct a 100-ft test strip of fog seal and adjust the application rate as needed and to ensure that a uniform appl
19、ication of the emulsified asphalt is applied with no streaking. Apply the fog seal to minimize the amount of overspray and do not allow traffic on the fog seal until it has cured. Note 1Care should be taken to ensure that the fog seal application r ate does not have an adverse effect on the surface
20、texture. 4.5. Ring Test: 4.5.1. Sweep the section of road to be fog-sealed clean of debris and dust. 4.5.2. Draw two or three 6-in. diameter circles on the swept pavement. 2017 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation
21、of applicable law.TS-2a PP 88-3 AASHTO 4.5.3. Select two or three target application rates and translate them to the required volume of emulsified asphalt from Table 2. 4.5.4. Label each circle with its application rate. 4.5.5. Use a suitable measuring instrument such as a 10-mL graduated cylinder t
22、o pour the required amount of emulsified asphalt into each circle. Evenly distribute the material within the circle with a small brush. 4.5.6. The ideal application rate will evenly and completely cover the pavement within the circle, with no emulsified asphalt draining outside. 4.5.7. Record the op
23、timal application rate. Note 2Fog seals may be applied at a higher application rate or at higher residue contents for chip seal applications or for open-graded hot mix surfaces. Normally the ring test is used only when the pavement surface has relatively low permeability, which could result in a sli
24、ppery pavement following application. Table 2Amount of Emulsified Asphalt for Ring Test gal/yd2mL (6-in. Circle) 0.06 5.0 0.07 5.8 0.08 6.6 0.09 7.4 0.10 8.3 0.11 9.1 0.12 10.0 0.13 12.8 4.6. All design work will be performed using the emulsified asphalt to be used on the job site or from equivalent
25、 material from the same source and having substantially the same material properties. 5. REPORT 5.1. Report the emulsified asphalt residual rate to the nearest 0.01 gal/yd2. 6. KEYWORDS 6.1. Emulsified asphalt; fog seal; surface seal. 1This provisional standard was first published in 2017. 2017 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.
