Preparing an Aggregate Surface (Prime Coat)
Posted by Jesse Willoughby on Fri, May 08, 2009 @ 05:06 AM
Liquid asphalt materials with high penetrationqualities are used for prime coats. They are sprayed onto an aggregate surface,where they coat and bond the aggregate. Prime coats provide a temporarywaterproofing of the base course surface and a permanent bond between the basecourse and asphalt concrete pavement. Prime coats may also preserve thefinished base coarse for a few days if traffic must be allowed on it beforepaving begins, especially in wet weather. They also provide a zone oftransition in asphalt content between the pavement and the untreated materialbelow.
Occasionally priming is deleted from a paving project.This may be considered late in the season when air temperatures are too coldfor priming but still allows paving. Prime coats serve a real purpose in thepavement structure, however, so deletion is normally not allowed. Deletion of aprime coat must be approved at the Regional level.
Sometimes an asphalt treated base is usedinstead of a primed base.