Substrates such as aggregates, particularly for roadbuilding, are coated with asphalt by foaming the asphalt and mixing the hot asphalt foam with the aggregate. The asphalt is foamed by dispersing water in the hot asphalt as to maintain the water in the liquid phase and then vaporizing the water to form...http://www.google.de/patents/US4692350?utm_source=gb-gplus-sharePatent US4692350 - Asphalt coating method
