As part of the maintenance program, crews chip seal street surfaces (including new streets) to protect from water and weather damage and to keep them in good condition.
A chip seal application to a road or street has many positive benefits:
Maintains the existing pavement in its present condition by delaying further aging due to water and sun - this is equally important to new streets
Changes the texture of the road for skid resistance
Supplies minimal additional strength to the pavement
Provides a moisture barrier
Gives better resistance to studded tires
Corrects existing pavement problems by sealing cracks
How is it Done?
The road surface needs to be properly cleaned of debris and any holes patched.
An asphalt distributor truck starts by shooting
one lane at a time with hot liquid asphalt
to assure an even application. The asphalt used is applied at a
temperature between 140 and 180 degrees Fahrenheit. After cooling,
this asphalt remains slightly flexible to maintain its hold on the rocks.
The chip spreader, follows as close behind as possible with a
rock application, preferably within one minute. The asphalt must be fluid so the rock will
be embedded into the asphalt. The rocks are an aggregate crushed to a special specification
for size and cleanliness
A rubber-tire roller is used to set the rock into the fresh oil.
This is done in order to press the flat sides of the rock down and produce a tighter chip seal. It takes two to four passes of
the roller to set the rock.
After the first lane has been shot,
covered with rock and the rolling has begun, the equipment starts the second lane.
The process is repeated.
Sweeping is done at the completion of the chip seal process to
remove surplus rock from the surface. This loose rock can grind and loosen rock set in the chip seal and
damage the project. Sweeping is done as soon as possible after the asphalt has set up, normally within three to seven days.
ACHD follows each chip seal with a fog seal which helps retain any remaining rock,
control dust, and provide a clean canvas for new pavement markings. Fog sealing also adds life to a chip seal. This is a separate process that follows sweeping
by up to three weeks