Pavement Preservation Journal, Winter 2013, Vol. 6, No. 4
Polymer modification can enhance the performance of fog seals, experience is showing.
As the awareness of the benefits of fog seals has increased and as pavement preservation is more widely embraced, agencies are looking for increased performance, and information about industry best practices. One way to boost fog seal performance is by polymer modification.
WHAT IS A FOG SEAL?
A fog seal is the spray application of a thin layer of asphalt emulsion to the pavement surface, and constitutes an easy first step toward a full pavement preservation program. Fog seals protect the pavement from oxidation and environmental degradation, as they replace the surface layer of asphalt binder lost due to traffic wear, while helping seal minor hairline cracks.
Their application is simple and cost-effective, but must be evenly applied to the full lane. The emulsion cure time can be adjusted to the needs of the project. These applications have been used on surfaces of every type; fog seals may be used on low traffic roads, city streets, parking lots, and even interstate highways.
The asphalt emulsions used in fog seals may be diluted to a lower residue content to allow for better control during application. The penetration of the residue is similar to the asphalt binder used in the same local climate. Some agencies have separate specifications for fog seal emulsions.
Polymer modification of asphalt has been in use for decades and its benefits have been well documented. Today, BASF’s Acronal NX 4627 polymer modifier is being used to provide a more robust fog seal for high-stress pavements. The polymer provides a strong bond with better long-term performance, and can also be used to modify most types of emulsions.