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.