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While private contractors complete large projects
that are planned far in advance of the actual work, the day-to-day
maintenance of Las Vegas streets falls primarily on the shoulders of city
street maintenance forces.
Chris Finberg of the Las Vegas Department of Field
Operations is one of those shouldering the responsibility for Las Vegas
Street maintenance. Like most Las Vegans who live and work in the city,
Finberg is not a gambler, but in the same dynamic spirit of the city’s
growth and progress, he is open to ideas that improve, simplify, and lower
street maintenance cost. Finberg and Bill Hinkel, crew leader, devised a
program for simple asphalt repairs that support heavy traffic. For two years
Finberg and his crews have repaired heavily traveled asphalt streets quickly
and simply with fewer workers and less equipment while completing more
repairs than ever. The new repair system eliminates the grinding or dig-outs
normally required before conventional hot-mix repair and no asphalt waste is
generated to haul away when repairs are complete.
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The crew checks area needing repair |
Material is simple to use. |
The
repair is quick and low cost. |
Arterial streets with their high traffic volume are
difficult to maintain and one of Finberg’s biggest challenges. “These roads
carry more cars. Everybody that lives in a neighborhood goes to one of those
to get somewhere. These roads represent a huge investment. Roads were built
based on traffic projections, but for everything built in the [Las Vegas]
valley the projections have been exceeded many times over.
“Many of Las Vegas’ roads are not designed for the
traffic loads they now have to carry and are exhibiting pavement distress.
Even though we are in a desert, these roads still need protection from water
intrusion which deteriorates the base and leads to structural failure.
“The problem with communities and government is
their needs exceed available budgets.”
Communities and governments must operate within
budgets and spending limits. For growth communities, roads are built that
may become structurally obsolete when traffic volume exceeds projections.
The investment in roads is enormous, and they must
be maintained to extend their service life beyond the normal design of 20
years. Rapid deterioration begins by the 15th year under normal conditions.
In the Las Vegas climate, with low humidity, year-round sunshine, and high
summer temperatures, asphalt quickly loses its flexibility and distress
begins. With traffic that exceeds original design limits, rapid pavement
deterioration is inevitable. At $420,000 per centerline mile for asphalt
pavement reconstruction on an arterial roadway, maintenance for these
heavily traveled streets is a must to delay more expensive reconstruction.
What kind of repairs?
On Las Vegas arterial streets, full-depth patching
with hot mix is the usual repair for deteriorated pavement sections. When
there is sub-base failure, the entire lane width is removed and the sub base
is restored. The asphalt is placed and compacted in lifts. Typical repairs
require several tons of asphalt, specialized equipment, truck transport to
deliver and remove materials, adequate time to complete the work, and a
skilled-labor crew.
With conventional full-depth hot-mix repairs, a
single repair represents a lot of work, materials, and equipment, but
according to Finberg, “A patch is always inferior to the original pavement
because it weakens the surrounding overall structure.”
With inferior results from conventional patching
compared to new pavement, the notion of simple repairs with no pavement
removal was tempting to Finberg. Is it possible to mitigate future pavement
distress without pavement removal? This is what Finberg is learning.
For years, polymer repairs of small surface damage
on Las Vegas residential streets have been successful. The repair has been
performed using a mix of sand with a thin liquid polymer, Dopey Soup,
supplied by Vern Phillips of Construction Sealants Supply of Las Vegas.
In new Las Vegas subdivisions, streets are completed
first. This provides easy access for completing home construction. Heavy
equipment moving in and out during construction damages streets. A flowable
mix of Dopey Soup and sand is used to repair this type of damage.
Before final acceptance, repairs are completed and
the entire street is slurry sealed to restore new appearance. First repairs
on these residential subdivisions began some 10 years ago. These small
repairs for new asphalt under light residential traffic perform well in this
desert climate.
With the help of Vern Phillips, these residential
street repair methods were adapted for repair of heavily traveled arterial
streets. The repair composition was improved to simplify larger repairs.
Repair kits with a treated sand mixture, A and B liquids, plus special
black-topping sand was devised.
The sand was coated black to match the appearance of
asphalt and to eliminate silica sand’s affinity to moisture that could be
detrimental to its bond to the polymer binder. The treated sand is
hydrophobic, does not wet out with water, and forms a high-strength,
flexible polymer concrete when combined with the liquid polymer. These
pre-weighed repair kits are complete and simple to use. With no measuring or
weighing required, reliable results are easily achieved.
Las Vegas city street maintenance forces further
developed application methods suited to the larger scale repairs for the
heavily traveled arterial streets. To perform the repair, the asphalt
pavement is air swept using compressed air from a high-pressure towable
compressor. Dirt and debris are removed from cracks, potholes, and raveled
surfaces by directing a high-pressure air stream slowly over the damaged
areas. A rapidly curing, flowable sand/polymer composition named FloMix, is
applied, cold, over the deteriorated pavement. The composition fills cracks,
ruts, and potholes to quickly restore the pavement to original grade. With
no pavement removal, material volume for repairs is small. Application is
quick. The repair material is leveled smooth to grade with an asphalt rake
and hand trowels. For pavement depressions, deep ruts, wide cracks, and
potholes, clean, dry crushed gravel is added to the mixture for higher
strength with reduced cost.
Advantages
Advantages include shorter and fewer lane closures.
Since the repairs are quick, they can be performed within short time frames
of low traffic volumes. A full-depth hot-mix asphalt repair requires about
three to four hours to complete, and may require an extra lane in the
closure to move equipment in and out of the repair. In contrast, the same
repair with the new process is finished in less than an hour and without the
need for an extra lane in the closure. The repair is traffic ready in one to
three hours. Most of the time saving comes from eliminating the laborious
removal and hauling of the existing pavement. With the new process, only the
lane under repair is closed to traffic, so impact on traffic flow is
significantly reduced.
Many repair projects are scheduled on Las Vegas’
lightest traffic day, Sunday. A single-lane closure is set up at 7 a.m. with
all other lanes remaining open to traffic. The closure is reopened to
traffic at 3:00 p.m. The necessary work is completed with a minimum
disruption to traffic flow.
Less equipment and manpower is another advantage.
Unlike conventional hot-mix repairs which required costly equipment and a
four-man skilled crew, the FloMix repairs are completed with just three
workers in one pickup truck using a compressor, a generator, a mixer, an
asphalt rake, and two trowels.
A FloMix crew can complete twice the number of
repairs in an eight-hour work shift than a hot-mix repair crew.
But the benefit of the system is not so much the
speed of repairs as the ability to respond to repairs with minimal delay.
The process eliminates the need for obtaining hot mix and requires only a
minimal, semi-skilled crew and limited equipment. This simplifies scheduling
work during off-peak traffic. The FloMix can be inventoried for repairs as
needed, 24/7. By eliminating dependence on a hot-mix plant schedule, repairs
are placed easily as needed, in hot or cold weather year round.
The material is simple to use. To Chris Finberg,
“It’s the simplicity as much as anything that is having us use this
material. The simplicity means entry-level employees can perform the work.
It’s our ability to use all levels of skill within our current staff [that
makes it appealing]. Our department workload includes essential tasks, which
require various degrees of skill. When you can perform work that
traditionally requires a high skill level and complete the task with less
skilled workers, that’s ideal.”
The ability to do repairs in house also eliminates
the administrative costs of managing outside contracts and the delays
associated with the bid process.
Promotions and turnover are a big problem with skill
work like hot-mix patching. Training entry-level workers for skilled work
takes time.
This is not a problem with the new repairs according
to Bill Hinkle, lead worker. “I may be the only person next year still doing
[these repairs]. Everybody else may be new. They’ve all moved on to other
places within the city, on to bigger and better things, but I can continue
with entry level people.”
Las Vegas city street maintenance workers, with
their broad range of maintenance responsibilities, are more effective by
using the polymer concrete repair kits which can be applied at any time with
minimal advance planning. Repairs are suited to virtually all small damage
and early pavement distress. The mixture has also been placed over wide
cracks and large potholes.
Finberg’s low-labor, rapid-repair methods simplify
maintenance with the ability to schedule repairs at any time, day or night,
year around. Lanes are closed to traffic for short times to create safe work
zones for placing repairs on arterial streets during off-peak travel times.
Often, only the lane needing repair has to be closed. The rapid repairs
substantially reduce the time needed for closures. The application rate is
two to three times faster than the rate of hot-mix asphalt repairs, allowing
more repairs to be completed within the closure period.
The repairs can be installed with a minimum of
equipment and without the need for skilled labor. This makes the technique
well suited for maintenance crews that have many responsibilities other than
road repair.
After the repair
The new repairs have been under heavy Las Vegas arterial traffic for only
two years. The performance is still under evaluation. Finberg says, “Two
years is not enough time to fully evaluate the performance of the polymer
repairs we have installed. I will feel more confident in its performance
after we evaluate it after three to five years. However, I will be
proceeding to use it even though there are certain risks associated with
using a new product and technique. This is the second year we have installed
the material, and its potential advantages make it well worth our
investment. I would have never started using this material if I didn’t think
that it has the ability to perform at an acceptable level.”
Reprinted from Better Roads Magazine
September 2004 |
By
repeatedly reinventing itself, this southern Nevada desert city has
remained one of the world’s premier tourist destinations, accommodating
35-million visitors a year in more hotel rooms than any other city in
the world.
