46 Scrub Seal ($$$$) A scrub seal is a pavement preservation technique that involves the application of a modified asphalt emulsion to the road surface, followed by the application of an aggregate cover. The uniqueness of a scrub seal compared to other seals is the use of a scrub broom (a broom with flexible bristles) to work the emulsion into the cracks and crevices of the pavement surface before the aggregate is applied. This process enhances the seal’s ability to fill cracks and ensures a better bond between the pavement and the seal. Here’s a step-by-step explanation of the scrub seal process: 1. Surface Preparation: The existing pavement is cleaned to remove debris, dust and other materials that may prevent good adhesion. 2. Emulsion Application: A modified asphalt emulsion is applied to the road surface using a distributor truck. The type of asphalt emulsion is selected based on existing pavement conditions and climate. 3. Scrubbing: Immediately after the emulsion is applied, a scrub broom that is attached to the distributor truck is used to work the emulsion into the pavement surface. The broom helps ensure that the emulsion penetrates into the cracks and voids, providing a better seal. 4. Aggregate Application: While the emulsion is still tacky, aggregate is spread over the surface. The aggregate type is chosen based on compatibility with the emulsion and desired surface characteristics. 5. Rolling: After the aggregate application, the surface is rolled with pneumatic tire rollers to embed the aggregate into the emulsion and to remove excess loose aggregate. 6. Curing: The scrub seal must be allowed to cure properly. This process involves the evaporation of water from the emulsion, leaving the residual asphalt to bind the aggregate to the pavement. 7. Sweeping: Once the curing is complete, any loose aggregate is swept from the surface. The benefits of a scrub seal include: • Crack Sealing: It effectively seals existing pavement cracks and prevents water infiltration, which can cause further pavement damage. • Improved Traction: The new aggregate surface provides enhanced skid resistance and improved safety. • Cost-Effective: As a pavement maintenance technique, scrub seals are less expensive than more extensive repairs or overlays. • Extended Pavement Life: By providing a protective layer, scrub seals can extend the service life of the pavement. • Correcting Minor Surface Irregularities: Scrub seals can help to fill small surface imperfections and improve ride quality. Scrub seals are typically used on aging asphalt surfaces that require sealing and minor surface correction. They are effective for roads with low- to moderate-volume traffic, and the process is relatively quick, minimizing traffic disruption.
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