Explanation of a Single Seal Coat

Application

• Asphalt is an oil-based surfacing agent that is composed of gritty aggregate material held together with liquid coal or tar. Liquid coal and tar hardens as it cools ultimately creating a smooth surface suited for vehicular traffic. This surface needs protection against water, sunlight and abrasion. Single seal-coats are applied only once and in one layer on top of aggregate material. Seal-coat provides a needed layer of protection

Types

• Asphalt's components range from fine, gritty sand to large, coarse crushed stones. The liquid portion is derived from coal or oil. These different components contribute to asphalt's wide range of available grades and surfacing capabilities. Single coat-seals are also varied. There are several different types of seals, each suited for a specific road condition or asphalt type. Seal-coat types include fog seals, sand seals, chip seals, multi-chip seals and slurry seals. The seal-coat is composed of a mixture of the asphalt's aggregate material combined with fillers and mixed with modified liquid asphalt that contains synthetic materials like rubber, latex or polymers.

Uses and Effects

• Single seal-coats protect asphalt from external stresses but do they do not help to improve a poorly constructed road. The seal-coat penetrates the aggregate, essentially closing off its pores, and limits the effects of pooling water. This not only protects the asphalt but also improves vehicle tire traction along the road's surface. Single seal-coat applications are made on older asphalt surfaces where they effectively seal cracks and imperfections without the need for resurfacing the entire roadway, parking lot or driveway.

Considerations

• Single seal-coatings are toxic, petroleum-based agents and should only be applied by licensed professionals. Stormwater run-off can leach toxic chemicals into groundwater. When excessive amounts of single seal-coats are applied, the potential for this damage can increase. Incorrect mixing and application can also increase the potential for toxic run-off and asphalt mismanagement.