Spray seal is a two coat liquid bitumen / aggregate treatment to existing or prepared surfaces. It offers a rougher surface than that of asphalt and is formed by spraying a layer of hot liquid bitumen and then covering the liquid layer with a layer of aggregate. Liquid bitumen is sprayed onto a prepared road base surface via a hand bar for small jobs or sprayer bar mounted underneath the truck for the larger areas. A 14mm or 10mm aggregate is spread in a uniform layer to base and rolled with a multi roller. A second coat of bitumen is then sprayed, followed by a layer of 7mm or 5mm aggregate (which fills the voids between the aggregate of the previous coat) and once again rolled with the multi roller.
The surface texture of a spray seal is course. Bitumen spray seals are suitable for many areas such as long driveways and country access tracks as a cost effective alternative to Asphalt paving. For lighter use applications or rejuvenation of an older firm surface, a single coat spray seal may be suitable.