AGGREGATE: The quality of aggregate is important to the overall success of the scrub 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. Local availability often constrains the quality of the aggregate, causing agencies to select lower-quality local aggregates based on cost and availability. Typically, aggregate selection is a function of geography where availability and transportation distance define the aggregate selection process. The aggregate is usually a crushed stone such as granite, slag, limestone, or other high-quality aggregate. Reclaimed asphalt could be a potential aggregate source if it is properly controlled and graded.
ASPHALT EMULSION: There are 2 types of emulsion that can be selected when constructing scrub seals, emulsion with rejuvenator and without rejuvenator. The selection of either is a function of the specification, history of scrub seals, and local availability of scrub seal emulsions. Most scrub seal emulsion can be modified with polymer. Some requirements that scrub seal emulsions should meet, regardless of type, are:
The emulsion should not bleed when applied at the appropriate rate.
At the time of application, the emulsion needs to be fluid enough to uniformly cover the surface and flow into cracks, yet viscous enough to not puddle or run off the pavement.
The emulsion should develop adhesion quickly and hold the aggregate tightly to the roadway surface.