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What is the purpose of a prime coat and is it necessary on a new paving project?

A prime coat is an application of a low viscosity asphalt to a granular base in preparation for an initial layer (or surface course layer) of asphalt. The purpose of the prime coat is; to coat and bond loose material particles on the surface of the base, to harden or toughen the base surface to provide a work platform for construction equipment, to plug capillary voids in the base course surface to prevent migration of moisture, and to provide adhesion between the base course and succeeding asphalt course. After applying the prime coat, it must cure for a minimum of 48-72 hours before asphalt is placed, with no rain in the forecast.

At one time it was thought that a prime coat was an essential element of good pavement construction. However, in recent years many engineers have eliminated the use of a prime coat in their specifications, especially when asphalt layer(s), is 4 inches or more in thickness. In many instances, prime coats are not used even when surface thickness has been as thin as 2 inches. According to studies performed by The Asphalt Institute over the last 20 years, few if any, pavement failures can be attributed to the lack of a prime coat. We at Asphalt Enterprises, Inc. concur with the outcome of these studies.

Learn more about the asphalt related services we offer in the metro Atlanta area:

Asphalt Paving | Asphalt Overlays | Full-depth Reclamation & Pulverization | Asphalt Milling | Asphalt Crack Repair | Asphalt Sealcoating | Parking Lot Striping | Asphalt Maintenance & Repair | Other Services

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