Foam Bitumen is produced by foaming standard bitumen grade C170. The process consists of adding small amounts of water usually 2 to 3% by mass of the bitumen. The water is injected in conjunction with air to hot bitumen, which has been heated to between 170 and 180 degrees Celsius. When injecting the water at high pressure the water evaporates instantaneously forming a bubble surrounded by oil, this causes the bitumen to expand to around 20 times its original volume.
This increased volume results in a reduction of the viscosity of the bitumen. The bitumen foam is then injected into a mixer via injection nozzles which is then eminently suitable for mixing with cold and moist construction materials. This process creates a visco-elastic material which once it is compacted it is strong, moisture resistant, flexible, non-temperature sensitive and durable. Foamed bitumen is a unique pavement treatment for treating new materials or rehabilitating existing pavements that have exceeded their serviceable life.
This is how Foamed Bitumen is produced in the Laboratory