Chip Seal (Asphalt Surface Treatment/ Tar and Gravel ...- rate of spray of bitumen emulsion for surface dressing of roads ,Asphalt Surface Treatment (often referred to as chip seal, tar and gravel, BST-Bituminous Surface Treatment) is a widely used and very cost effective way to pave and maintain roadways, parking lots, driveways, and more.23 - Bitumen emulsions - Modifications of bitumen and ...For example, in a surface dressing context, the emulsion has to remain as a stable emulsion during application, so as to provide an even carpet of bitumen. And also, adequately adhere to the chippings.