# Fog Seals

A fog seal is a light application of a diluted slow-setting asphalt emulsion to the surface of an aged (oxidized) pavement surface. Fog seals are low-cost and are used to restore flexibility to an existing HMA pavement surface.

- Canonical URL: https://pavementinteractive.org/reference-desk/maintenance-and-rehabilitation/maintenance/fog-seals/
- Last updated: 2018-09-19
- Review: reviewed by licensed professional engineers on the previous Pavement Interactive site, where reviewers were not recorded by name

A fog seal is a light application of a diluted slow-setting [asphalt emulsion](https://pavementinteractive.org/reference-desk/materials/asphalt/emulsified-asphalt/) to the surface of an aged (oxidized) pavement surface. Fog seals are low-cost and are used to restore flexibility to an existing HMA pavement surface. They may be able to temporarily postpone the need for a surface treatment or non-structural overlay.

![Maintenance patch on a longitudinal joint covered by a fog seal.](https://pavementinteractive.org/wp-content/uploads/2008/07/Fog_seal1.jpg)

![Parking lot showing no treatment on the left side and a fog seal on the right side.](https://pavementinteractive.org/wp-content/uploads/2008/07/Fog_seal2.jpg)

*Figures 1 and 2.* Maintenance patch on a longitudinal joint covered by a fog seal. Parking lot showing no treatment on the left side and a fog seal on the right side.

Purpose

[Preventive maintenance](https://pavementinteractive.org/glossary/preventive-maintenance/). Fog seals are used to restore or rejuvenate an HMA surface. They may be able to postpone the need for a BST or non-structural overlay for a year or two.

## Materials

Slow-setting [asphalt emulsion](https://pavementinteractive.org/glossary/asphalt-emulsion/).

## Mix Design

None beyond the manufacturer's. A test patch may be needed to determine the proper application rate.

## Other Info

Fog seals are suitable for low-volume roads which can be closed to traffic for the 4 to 6 hours it takes for the slow-setting asphalt emulsion to break and set.

An excessive application rate may result in a thin asphalt layer on top of the original HMA pavement. This layer can be very smooth and cause a loss of [skid resistance](https://pavementinteractive.org/reference-desk/pavement-management/pavement-evaluation/skid-resistance/). Sand should be kept in reserve to blot up areas of excess application.