 Application

As with any paving project, the treatment is most effective when placed with good construction practices.

Lessons Learned:

The checklists to the right here should be followed.  Additional lessons learned from this study are given below.

·         Equipment

Asphalt distributors from a number of manufacturers were used on the field projects in this study.  (See equipment appendix.)  All gave good results, as long as they were properly set up for light emulsion applications and correctly calibrated. However, a number of adjustments were made during the trials.  It is important to recognize that fog seal applications are much lighter than those typically used for chip seals, but a complete, uniform coverage must be achieved for the pavement to be properly sealed.  It is important to remember that travel speed of the asphalt distributor determines bar pressure, and bar pressure impacts application rate and optimum nozzle size.  Recommendations for equipment settings as published by the Asphalt Emulsion Manufacturers Association (www.AEMA.org) or the equipment manufacturers describe industry best-practice.

The following checklist covers critical elements in the application process:

·         Calibration, Spray Bar Settings & Nozzles

The primary complaint of poor fog seal construction is improper nozzles--the right type of nozzle, the right angle, the right spray pattern and clogged nozzles. The height of the spray bar and bar pressure also determines the spray pattern, so that should be properly adjusted, as well.

It is also strongly recommended that a test strip be a pay item to help determine the correct application rate, as well as ensuring proper equipment operation and calibration.

·         Application Rates

There were a number of different materials used in this study, with application rates varying from 0.06 to 0.15 gal/yd².  Emulsion residue contents and dilution ratios also varied markedly. It is important to compare application rates, costs, and performance at comparable applied emulsion residue content. The suppliers generally had the best knowledge of their products.  Therefore, the supplier should be consulted for the correct range of shot rates for their product given the surface to be treated. 

·         Climatic Conditions

The surface and air temperature recommendations of the agency for emulsion applications and the suppliers’ recommendations for their products should be followed.  Typical minimum pavement temperatures at time of application ranged from 40-60°F and rising in the shade.  Also, rain should not be imminent, and there should be no freezing before the product is fully cured. 

·         Traffic Control

A test strip will also be helpful in determining cure time and when it is safe to return traffic.  Because of the reduced friction immediately after sealing, and of the danger of tracking the material, strict traffic control with the use of pilot cars is strongly recommended.

From the field tests and observations in this study, traffic should not be returned to full speed until the friction is at an acceptable level determined by the type of traffic and road configuration.

·         Sanding

Sanding on the 2006 projects showed an immediate increase in friction. The manufacturers of some of the rejuvenator products recommend sanding on their products because of the oily coating on aggregate surfaces.  In this study, the rejuvenators did best when sanded after they were allowed to penetrate and cure.  The harder residue asphalt emulsions did better when the sand was applied before the emulsion could break. Some of the manufacturers say that sanding is not needed, and that was the case in this study, especially on the chip seals and more open surfaces.  The application rate and type of sand are also factors to be considered.  When sand is applied, it is recommended that a high quality, crushed sand with adequate fine aggregate angularity (FAA) be used to give the desired friction numbers.  The sand should also be sufficiently small to prevent damage to windshields, and it should be relatively dry to avoid slowing cure.  For specifications, a saturated surface dry condition is probably the maximum amount of moisture that should be allowed.

Loose sand can itself cause a loss in friction, so brooming at the earliest possible time following curing is important. Sand also creates clean-up problems for curb-and-gutter or other urban applications where surface water drains might be plugged. Hence, some agencies prefer sand be avoided.  For some of the products tested, sanding is not necessary if traffic is kept off until the seal has cured. The supplier's recommendations should be followed.

Fog Seal Application Checklist

(Courtesy of the Foundation for Pavement Preservation 

& FHWA) 

Printed copies are available from FHWA and FP2 at 
www.pavementpreservation.org

 Click here for a downloadable copy of the Fog Seal Checklist

Click here for a downloadable copy of the Rejuvenator Checklist

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

o         Exercise care if coal tar oils are 
included in formulation

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 dilution 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.

Pre-application 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 the application rate range
should be:

¨       Take a 1/2 L can of diluted emulsion and 
pour it evenly over an area about 1 m2 
(or take a 1 pint can of the diluted emulsion 
and pour it evenly over an area about 1 yd2).
(Note: conversions are 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 (RECOMMENDED FOR CALIBRATION)

¨       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 
(RECOMMENDED FOR RANDOM CHECKS)

¨       Park the distributor on level ground. Measure 
and record the number of L (gal) of emulsion.

¨       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 f
or 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

¨       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 travel way.

¨       Excessive emulsion application or spills are removed.

Common Problems and Solutions

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. bar pressure is too high.

6. Nozzle is plugged.

Emulsion bleeding or flushing occurs:

1. Emulsion application is too high.

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

Application Guides. 1992. 

Asphalt Emulsion Manufacturers Association.

Annapolis, MD

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. 

Washington, DC:

Federal Highway Administration.
 

Rejuvenator Seal Application Checklist

Preliminary Responsibilities

Project Review

¨       Is the project a good candidate for a rejuvenator 
seal?

¨       Has the friction been tested; is the expected 
reduction in friction acceptable? 

¨       What is the existing surface type?

¨       Has an assessment been made of the surface 
absorption?

¨       Has much stone been lost?

¨       Does bleeding or flushing exist?

¨       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

o         Exercise care if coal tar oils are included in 
formulation

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.

Pre-application 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, low friction 
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 the application rate range 
should be:

¨       Take a 1/2 liter can of diluted emulsion 
and pour it evenly over an area about 1 m2 
(or take a 1 pint can of the diluted emulsion 
and pour it evenly over an area about 1 yd2).  
(Note: conversions are 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.

¨       Alternately, a Ring Test CT 345 (California Method Of 
Test For Determining The Quantity Of Asphalt 
Rejuvenating Agent Required For An Asphaltic 
Pavement.  
http://www.dot.ca.gov/hq/esc/ctms/CT_345.pdf) 
may be used.

Checking Application Rates

Emulsion Method A (RECOMMENDED FOR CALIBRATION)

¨       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 
(RECOMMENDED FOR RANDOM CHECKS)

¨       Park the distributor on level ground. Measure and record 
the number of L (gal) of emulsion.

¨       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.

¨       Traffic is not returned to full speed until the friction 
has been tested and judged to be at an acceptable level.

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. 

¨       Sand should not be applied until the emulsion has 
broken or been completely absorbed into the surface.  
Otherwise, the sand may form a low friction slurry 
with the emulsion.

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 
rejuvenator 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

¨       Brooming begins as soon as possible only if 
sand is applied.

¨       Brooming should be light and done once to 
remove excess only.

Opening the Rejuvenator 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.

¨