In asphalt pavement construction and maintenance projects, adequate bonding between constructions lifts and especially between the existing road surface and an asphalt overlay is critical in order for the completed pavement structure to behave as a single unit and provide adequate strength. If adjacent layers do not bond to one another they essentially behave as multiple independent layers – none of which are designed to accommodate the anticipated traffic-imposed bending stresses. Inadequate bonding between layers can result in delamination (de-bonding) followed by longitudinal wheel path cracking, fatigue cracking, potholes, and other distresses such as rutting that greatly reduce pavement life.
A good layer bond between the individual asphalt layers is necessary for a long service life of the asphalt pavement. For many years, bitumen emulsions have been used to bond the layers together in accordance with the requirements and bitumen sprayers are being used for applying prime coat and tack coat for adequate bonding of asphalt layers to adjacent base or asphalt layer. By effectively distributing bitumen emulsions, bitumen sprayers ensure the optimal bonding of pavement layers, resulting in long-lasting and durable road surfaces.
The bitumen sprayer is designed to distribute the bitumen evenly over the surface, ensuring that the asphalt adheres properly and forms a strong, durable surface. Typically, bitumen is heated to temperatures between 150°C (302°F) and 190°C (374°F) before being sprayed onto the road surface. These high temperatures are necessary to liquefy the bitumen and make it easier to apply and spread evenly. The bitumen sprayer consists of a tank that holds the bitumen, a heating system to keep the bitumen at the right temperature, a pump to circulate the bitumen, a spray bar with nozzles to distribute the bitumen, and controls to regulate the flow and pressure of the bitumen.
The bitumen sprayer is typically mounted on a truck or trailer and operated by a trained operator. The operator drives the sprayer along the road while spraying the bitumen onto the surface. The speed at which a bitumen sprayer operates can vary depending on factors such as the type of equipment, road conditions, and project requirements. However, in general, bitumen sprayers typically operate at a speed range of 5 to 15 kilometres per hour. This range allows for effective and controlled application of bitumen (asphalt) on road surfaces, ensuring proper coverage and adherence to the roadbed. The spray bar can be adjusted to vary the width and thickness of the layer of bitumen, depending on the specific requirements of the project.