Analyze Existing Fog Seal Asphalts and Additives: Literature Review (0-5091-1)

Fog and rejuvenating seals have the potential to reduce and reverse the aging of asphalt pavements, reduce cracking and raveling, and provide a better, longer-lasting pavement. The purpose of a fog seal is to coat, protect, and/or rejuvenate the existing asphalt pavement. Also, a fog seal can be used to decrease the permeability to water and air. To the extent such permeability reductions occur, a pavement's waterproofing will be improved and aging susceptibility due to binder oxidation will be reduced. Fog seal emulsions must penetrate into the voids in the pavement in order to seal off the surface. A slow setting emulsion diluted in water turns out to be a suitable fog seal material in this case. An emulsion that is too thick may not properly penetrate into the surface voids and will leave behind an excess amount of asphalt on the surface after the emulsion breaks, causing a slippery surface. Rejuvenating emulsions contain oils that reduce the viscosity of an existing asphalt, thereby reducing the cohesive failure of the asphalt as the flexibility of binder is improved. In addition, rejuvenating oils can penetrate to fill voids in the pavement and minimize further binder oxidation since the rate of asphalt oxidation is highly dependent on the voids in the total mixture (VTM). An effective rejuvenator must penetrate into the pavement surface in order to be absorbed by the aged hardened asphalt, but also to avoid causing a binder-slick surface, especially in wet weather. This report summarizes literature reports on fog seal and rejuvenator practices and research.