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The first concrete street built in the United States was an 8 ft
(2.4 m) wide strip of Main Street completed in 1891 in Bellefontaine,
Ohio. Local residents were so pleased with the artificial stone road,
scored to provide better footing for horses, that much of downtown
Bellefontaine was paved with concrete several years later.
Many municipalities today choose concrete pavement because of its
reputation for long-term serviceability and a sense that it provides
better value for the investment. Today, concrete has become the least
expensive alternative for new construction on a first-cost basis in
addition to maintenance costs being generally lower. A 10-year survey
concluded in the mid-1980s of 2,000 miles (3200 km) of municipal streets
in Kansas revealed that asphalt pavement was nine times as expensive
to maintain as concrete.
Aesthetic considerations, coupled with concrete's ability to reflect
light and heat, have made it the paving material of choice for many
cities. Because of its light color, concrete can mitigate the urban
heat island effect, reducing smog and promoting better air quality.
It also reflects from 33% to 50% more light than asphalt so cities
can achieve the same street lighting standard, satisfying American
National Standards Institute criteria, with a lower initial investment
in lighting fixtures and equipment, and, as well, can sustain considerably
lower long-term energy costs.
Fast- track paving techniques, in which the use of a high-early-strength
concrete mix allows the road to reopen in as few as 12 hours, have increased
the attractiveness of concrete for city street paving because of the
inconvenience of closing busy urban routes.
Rehabilitation Technologies
Concrete overlays, both bonded and unbonded provide cost effective
rehabilitation of aging urban asphalt paving. The process involves
overlaying a stratum of concrete on top of an asphalt road that needs
rehabilitation because of rutting, shoving, or other types of deterioration.
While unbonded concrete overlays require a thickness of 5 to 7 in.
(12.7 to 18 cm) on secondary roads, and from 8 to 12 in. (20 to 30
cm) on primary roads, bonded conrete overlays require a thickness
of only 2 to 4 in. (5 to 10 cm).
Early test results indicate that the thinner layer of high-strength,
fiber-reinforced concrete performs adequately because the concrete
creates a structural bond with the prepared surface of the asphalt
below. It becomes, in essence, a composite pavement. Joints are spaced
closer together than with conventional concrete pavement, usually
about 12 to 18 in. (30 to 40 cm) apart for each inch of concrete depth.
This helps ensure the bond between the concrete and asphalt below,
especially in freeze/thaw conditions where differential movement of
the two materials would be anticipated. Although further long-term
research needs to be done on the technology, bonded concrete overlays
could be valuable for rehabilitating high-traffic city streets and
intersections.
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