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Pavement Preservation Checklist logo

04: Fog Seal Application Checklist

This checklist is one of a series created to guide State and local highway maintenance and inspection staff in the use of innovative pavement preventive maintenance processes. The series is provided through the joint efforts of the Pavement Preservation Program of the Federal Highway Administration (FHWA) and the Foundation for Pavement Preservation (FP2).

FHWA uses its partnerships with FP2, the American Association of State Highway and Transportation Officials, and State and local transportation agencies to promote pavement preservation.

To obtain other checklists or to find out more about pavement preservation, contact your local FHWA division office or FP2 (at http://www.fp2.org/), and check into these Web pages:

Preliminary Responsibilities

Project Review

  • Is the project a good candidate for a fog seal?
  • What is the existing surface type?
  • Has an assessment been made of the surface absorption?
  • Has much stone been lost?
  • How much bleeding or flushing exists?
  • Review project for bid/plan quantities.
  • What is the relative cost?

Document Review

  • Bid specifications
  • Special provisions
  • Agency requirements
  • Emulsion specifications
  • Traffic control plan
  • Material safety data sheets

Materials Checks

  • Asphalt emulsion selection: type and dilution rate.
  • The emulsion is from an approved source (if required).
  • The emulsion is sampled and submitted for testing (if required).
  • The water to be used is compatible with the emulsion.
  • The emulsion temperature is within application temperature specifications.
  • Sand, if required, is within specifications and dry.

Preapplication Inspection Responsibilities

Surface Preparation

  • The surface is clean and dry.
  • All pavement distresses have been repaired.
  • The existing surface has been inspected for drainage problems.

Equipment Inspections

Broom for Cleaning Existing Surface
  • Bristles are the proper length.
  • The broom can be adjusted vertically to avoid excess pressure.
Spray Distributor
  • The spray bar is at the proper height.
  • All nozzles are uniformly angled 15° to 30° from the spray bar.
  • All nozzles are free of clogs.
  • The spray pattern for uniformity and proper overlap (double or triple) has been checked.
  • Application pressure has been checked.
  • The distributor's application calibration has been checked.
  • There is a working and calibrated thermometer on site.
  • Water has been added to the emulsion in correct proportion and circulated. There is no foam.
Sand Spreader
  • Each gate control and settings have been checked.
  • Sand is free flowing.
  • The chip spreader's calibration across the entire chipper head has been checked.
  • The truck hookup hitches have been checked.
Haul Trucks
  • The truck box is clean and free of debris and other materials.
  • The truck hookup hitch is in working order.
  • If a truck box apron or extension is required for loading the sand spreader, it is available.
All Equipment
  • All equipment is free of leaks.
  • All equipment is calibrated and clean.
Weather Requirements
  • The minimum surface and air temperature requirements have been met (default 15 °C; 59 °F).
  • Air and surface temperatures have been checked at the coolest location on the project.
  • Air and surface temperatures meet agency requirements.
  • Note: High winds can create problems with the diluted emulsion application.
  • Note: High temperatures, humidity, and wind will affect how long the emulsion takes to break.
  • The application of emulsion does not begin if rain is likely.

Determining Application Rates

  • Agency guidelines and requirements are being followed.
  • The absorption ability of the surface has been checked.
  • More emulsion can be applied to dried-out and porous surfaces.
  • More emulsion can be applied on roads with low traffic volumes.
  • Do not apply to smooth, nonporous, and asphalt-rich surfaces.
  • Less emulsion must be applied on roads with high traffic volumes.
  • Does the emulsion soak into the surface?
  • If the texture is high, spray should be in both directions to avoid rain-shadow effects.

Method for Determining Emulsion Application Rates

To get an idea of where on the range the application rate should be,

  • Take a 1 L can of diluted emulsion and pour it evenly over an area about 1 m2 (or take a 1 qt can of the diluted emulsion and pour it evenly over an area about 1 yd2) (note: conversion is approximate).
  • If the emulsion is not absorbed into the surface, decrease the amount and apply to a new 1 m2 (or 1 yd2) area. Repeat the trials until the approximate application rate is found.
  • If the surface looks like it will absorb more emulsion, increase the amount and apply over a new 1 m2 (or 1 yd2) area. Repeat trials until the approximate application rate is found.

Checking Application Rates

Emulsion - Method A
  • Record the weight of a .84 m2 (1 yd2) pan or nonwoven geotextile material.
  • Place the pan or geotextile on the road surface.
  • Have the distributor apply emulsion over the pan or geotextile.
  • Record the weight of the pan and emulsion or the geotextile with emulsion.
  • Subtract the two weights to determine the weight of the emulsion applied.
Emulsion - Method B
  • Park the distributor on level ground. Measure and record the number of L (gal) of emulsion (note: not a conversion).
  • Measure off a known area for a test section.
  • Have the distributor apply emulsion to the test section.
  • Park the distributor on level ground and remeasure the emulsion.
  • Subtract the two measurements to obtain the volume of emulsion applied.
  • To determine the application rate, divide the amount of emulsion applied by the test area-L/m2 or gal/yd2 (if using feet, length x width/ 9 = yd2).

Traffic Control

  • The signs and devices used match the traffic control plan.
  • The setup complies with local agency requirements or the Federal Manual on Uniform Traffic Control Devices (MUTCD).
  • Flaggers do not hold the traffic for extended periods of time.
  • Any unsafe conditions are reported to a supervisor (contractor or agency).
  • The pilot car leads traffic slowly-40 kph (24 mph) or less-over the fresh seal coat.
  • Signs are removed or covered when they no longer apply.

Project Inspection Responsibilities

Sand Application (where used)

  • Enough trucks are on hand to keep a steady supply of sand for the spreader.
  • Application starts and stops with neat, straight edges.
  • Application starts and stops on building paper.
  • No emulsion is on top of the sand.
  • Application is stopped as soon as any problems are detected.
  • Application appears uniform.
  • Checks are made for streaks and plug-ups.

Emulsion Application

  • Building paper is used to start and stop emulsion application for straight edges.
  • Emulsion is within the required application temperature range.
  • Application appears uniform.
  • Checks are made for drilling and streaking.
  • Nozzles are checked for plugging.
  • Random application rate checks are performed.
  • The distributor adjusts speed to match chip spreader speed to prevent stop-start operations.
  • The distributor is stopped if any problems are observed.

Truck Operation

  • Trucks are staggered across the fresh fog seal coat to avoid driving over the same area.
  • Trucks travel slowly on the fresh seal.
  • Stops and turns are made gradually.
  • Truck operators avoid driving over exposed emulsion.


  • Brooming begins as soon as possible only if sand is applied.
  • Brooming should be light and done once to remove excess only.

Opening the Fog Seal to Traffic

  • Traffic travels slowly-40 kph (24 mph) or less-over the fresh seal until seal is broomed and opened for normal traffic.
  • Reduced speed limit signs are used when pilot cars are not used.
  • After brooming, pavement markings are applied before opening pavement to normal traffic.
  • All construction-related signs are removed when opening pavement to normal traffic.

Cleanup Responsibilities

  • All loose sand from brooming is removed from the travelway.
  • Excessive emulsion application or spills are removed.

Common Problems and Solutions

(Problem: Solution)

  • Excessive splattering of the emulsion:
    1. Emulsion has been diluted too much.
    2. Bar is incorrectly set.
    3. Spray pressure is too high.
  • Streaking or drill marks are appearing in emulsion:
    1. Emulsion is too cold.
    2. Viscosity of the emulsion is too high.
    3. All nozzles are not at the same angle.
    4. Spray bar is too high.
    5. Spray bar is too low.
    6. Spray bar pressure is too high.
    7. Nozzle is plugged.
  • Emulsion bleeding or flushing occurs:
    1. Emulsion application is too high.


Information in this checklist is based on or refers to the following sources:

  • Application Guides. 1992. Annapolis, MD: Asphalt Emulsion Manufacturers Association.
  • Asphalt Emulsion Handbook,Manual Series No. 4. 2000. Lexington, KY: The Asphalt Institute.
  • Basic Asphalt Emulsion Manual,Manual Series No. 19. 1999. Lexington, KY: The Asphalt Institute.
  • Manual on Uniform Traffic Control Devices, Millennium Edition. 2000. Federal Highway Administration.

For more information on pavement preservation, visit these Web sites:

For more information on the Pavement Preservation Checklist Series, contact:

Construction and System Preservation Team
Office of Asset Management
Federal Highway Administration, HIAM-20
U.S. Department of Transportation
1200 New Jersey Avenue SE, Room 3211
Washington, DC 20590
E-mail: preservation@fhwa.dot.gov
Telephone: 202-366-1557

National Center for Pavement Preservation
Michigan State University
2857 Jolly Road
Okemos, MI 48864
E-mail: galehou3@msu.edu
Telephone: 517-432-8220

Foundation for Pavement Preservation
8613 Cross Park Drive
Austin, TX 78754
E-mail: fppexdir@aol.com
Telephone: 866-862-4587 (toll free)

September 2002
Publication No. FHWA-IF-03-001

Quality Assurance Statement

The Federal Highway Administration provides high-quality information to serve Government, industry, and the public in a manner that promotes public understanding. Standards and policies are used to ensure and maximize the quality, objectivity, utility, and integrity of its information. FHWA periodically reviews quality issues and adjusts its programs and processes to ensure continuous quality improvement.

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Updated: 11/30/2015
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