Transportation -
Pavement Maintenance Programs
A variety of programs are used
to help keep our streets in the best
possible condition and extend their service life. Below
are definitions of commonly used pavement maintenance
techniques.
When a small isolated section of roadway fails, we call it a
"pothole."
Typically water has seeped under the pavement
surface, creating pockets of water that fracture the surface when
traffic compresses the water underneath. These potholes are
temporarily repaired with a cold asphalt mix. If a section of roadway has
numerous failures because the sub-base under the road surface is
compromised, permanent repair may be delayed until a better solution can
be funded and implemented.
Asphalt pavement is designed to be flexible. This
allows it to adapt to the wide temperature swings we
have in Arizona. The flexing causes cracks to
develop in even relatively new pavement and this
will continue throughout the usable life of the
roadway surface. To limit deterioration,
cracks are filled with a rubberized sealant we call
a "Crack Seal" that will keep out water and fill
voids in the surface.
Three types of sealcoats may be applied that will
extend the life of the pavement. An Acrylic seal is a thin layer of
asphalt emulsion that prevents oxidation and adds asphalt material to
the surface course. For seal protection and added wear surface, a Slurry
seal mixture made of asphalt emulsion, water and sand may be applied. Chip
seal is a thin asphalt emulsion followed by small grade aggregate that
provides additional wear surface and sealing to the road surface.
If large areas of a roadway are showing signs of
structural failure, potholes or “alligator” cracking, the section can be
milled down to the good pavement base. This is followed by a new hot-mix asphalt
overlay, extending the life cycle of the original pavement.
When a roadway has reached the end of its life
cycle and can no longer be rebuilt, a new road must be constructed. All
existing pavement will be removed and recycled for use as a new sub-base.
The old sub-base will be regraded and compacted and a new hot-mix
asphalt surface applied.
The most common work seen on the road has nothing
to do with pavement maintenance. These are areas where utility crews are cutting
into the road surface, digging down below the surface to add or repair
sewer, gas, or water lines. During the course of
construction they will cover these areas overnight with metal plates or
an asphalt patch mix. When completed, the area will be re-compacted, a new sub-base installed and
a hot-mix asphalt applied. |
