The principal materials used to create slurry seal are aggregate, asphalt emulsion, and filler, which are mixed together according to a laboratory’s design-mix formula. Water is also added for workability.

Asphalt emulsions serve as a binder, holding the crushed aggregate together and adhering the new slurry surfacing to the old surface over which it is being applied. Various emulsions and aggregates are used to meet the conditions, specifications, and requirements of individual projects.

The aggregate must be clean, crushed, durable, properly graded, and uniform. The asphalt emulsion is a three-part system consisting of asphalt, water, and emulsifier. Fillers such as Portland cement, hydrated lime, or aluminum sulfate liquid are often used in small quantities as stabilizers or chemical modifiers.

Aggregate types:

• I (fine)

    - Fine aggregate mixtures are used for maximum crack penetration and sealing in low-density/low-wear traffic areas.

• II (general)

    - Type II aggregates are the most commonly used and are widely employed where moderate-to-heavy traffic is found. They seal, correct moderate-to-severe ravelling, oxidation and loss of matrix, and improve skid resistance.

• III (coarse)

       Type III corrects severe surface conditions — preventing hydroplaning and providing skid resistance under very heavy traffic loads.