Chapter 6: Fog Seals

Troubleshooting

This section provides information to assist field personnel in troubleshooting problems with fog seals, along with “dos and don’ts” that address common problems that may be encountered during the course of a project.

The troubleshooting guide presented in Table 2 associates common problems to their potential causes. For example, a slick surface may be caused by wet pavement, a high application rate, or rain. Cold weather could also contribute to slick pavements as the emulsion break may be delayed. The emulsion will be tacky and can be picked up by vehicles if the existing road surface is dry or dusty, or the wrong emulsion is used.

In addition to the troubleshooting guide, Table 3 lists some application problems and their recommended solutions.

Table 2: Troubleshooting Fog Seal Problems
	Slick Surface	Not Breaking	Washes Off	Tacky Picks Up	Will Not Dilute	Breaks Too Fast	Dilution Wrong
Cause	Problem
	Slick Surface	Not Breaking	Washes Off	Tacky Picks Up	Will Not Dilute	Breaks Too Fast	Dilution Wrong
Road Wet	• Yes	• Yes	• Yes	No	No	No	No
Road Too Dry	No	No	No	• Yes	No	• Yes	No
Road Dusty	No	No	No	• Yes	No	• Yes	No
Hard Water	No	No	No	No	Anionic	No	No
Alkaline Water	No	No	No	No	Cationic	No	No
Acidic Water	No	No	No	No	Anionic	No	No
Application Too High	• Yes	• Yes	• Yes	• Yes	No	No	• Yes
Application Too Low	No	No	No	No	No	• Yes	• Yes
Wrong Emulsion	No	• Yes	• Yes	• Yes	• Yes	• Yes
Rain	• Yes	• Yes	• Yes	No	No	No	No
Cold Weather	• Yes	• Yes	No	No	No	No	No
Hot Weather	No	No	No	• Yes	No	• Yes	No

Table 3: Application Problems and Related Solutions
Problem	Solution
Spattering of the Emulsion	Reduce the rate of dilution. Ensure the spray bar height is set correctly. Ensure the spray pressure is not set too high.
Streaking of the Emulsion	Ensure the emulsion is not too cold. Ensure the emulsion viscosity is not too high. Ensure the nozzles are at the same angle. Ensure the spray bar is not too high or too low. Ensure the spray bar pressure is not too high. Ensure all nozzles are not plugged.
Bleeding or Flushing of the Emulsion	Ensure the emulsion application rate is not too high. Check application and dilution rate and recalibrate sprayer, if necessary.
Surface Coefficient of Friction is too Low per ASTM E 274	Apply coating of clean dry sand. Sweep sand with rotary broom to absorb excess binder. Perform ASTM E 274. Repeat process until coefficient of friction is at least 0.30.

*Do not open treated surface until coefficient of friction is at least 0.30 as determined by ASTM E 274.

Dos and Don’ts

The following dos and don’ts list provides a quick reference to avoid making common mistakes with fog seals.

Do check water compatibility before dilution.

Do check dilution - has it been done, by whom, and when?

Do ensure that there is no contamination of the base emulsion by water, oils, or other liquids.

Do prevent contamination by other emulsions.

Do protect emulsions from freezing or localized boiling due to the application of direct heat.

Do heat emulsion gently and ensure heating coils are fully submerged (max 50°C (122°F)).

Do load from the bottom of tankers or sprayers to avoid foaming.

Do check equipment and nozzles.

Do check application rates.

Do exercise proper traffic control.

Do ensure the know-how is available on the job.

Do add water to emulsion, not emulsion to water.

Don’t store diluted emulsion longer than 24 hours.

Don’t continuously stir or circulate emulsion.

Don’t apply emulsion if air temperature is <10°C (50°F) and pavement temperature <15°C (59°F).

Don’t apply emulsion if rain or cool temperatures are imminent.

Don’t continue application if adequate breaking period is not available.

Don’t open treated surface to traffic until coefficient of friction is at least 0.30 as determined by ASTM E 274.