AGGREGATE: The quality of aggregate is important to the overall success of the chip seal program. Quality involves a number of constructability issues about using aggregates that are clean, durable, and abrasion resistant. The cover aggregate is expected to transfer the load to the underlying surface. It should provide adequate skid resistance and should be durable against climatic effects and traffic wear. Typically, aggregate selection is a function of geography where availability and transportation distance essentially define the aggregate selection process. Local availability often constrains the quality of the aggregate, causing agencies to select lower-quality local aggregates based on cost and availability. The aggregate is usually a crushed stone such as granite, slag, limestone, or other high-quality aggregate.
ASPHALT BINDER: There are 2 main types of binders selected when constructing chip seals, emulsified asphalt and hot asphalt cements. The selection of either is a function of the surface type, size of aggregate, compatibility with that aggregate and local availbility of binders. Some binders can be modified with polymer or tire rubber. Here are some requirments that binders should meet regardless of type:
The binder should not bleed when applied at the appropriate rate.
At the time of application, the binder needs to be fluid enough to uniformly cover the surface, yet viscous enough to not puddle or run off the pavement.
The binder should develop adhesion quickly and hold the aggregate tightly to the roadway surface.