Concrete Bridge Case Study
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Road Separation
Hawaii Bridge Uses New HPC Deck Mix
 The
North-South Road Separation structure carrying Interstate Route
H-1 over the newly constructed North-South Road will help to relieve
congestion in one of the fastest growing parts of Oahu. This prestressed
concrete spliced-girder bridge was constructed with a high-performance
concrete deck mix that aimed at reducing creep and shrinkage, while
employing a new type of air entrainment technology.
Hawaii is home to aggregates which, when used in concrete, may result
in concrete with large values for shrinkage and creep. To reduce
this, the design engineer, KSF, Inc., proposed using a new high-performance
concrete deck mix developed with Island Ready Mix and Miracon, Inc.
The contractor for North-South Road project Phase 1C, Kiewit Pacific
Co., and the State of Hawaii Department of Transportation, were
accommodating in implementating the new concrete mix that helped
limit creep and shrinkage.
The five-inch-thick cast-in-place high-performance concrete (HPC)
deck will be supported by 3-1/2-inch reinforced concrete deck planks
that span between the girder flanges. The deck planks serve as stay-in-place
concrete forms. The HPC deck was constructed with a 0.37 water-to-cementitious
materials ratio, and used a water reducer, a high-range water reducer,
a hydration stabilizing admixture, a viscosity modifying admixture,
a shrinkage-modifying admixture, a corrosion inhibitor, and a new
type of air entrainment. The new synthetic air entrainment, manufactured
by Miracon, is formulated using polymers. The HPC deck also was
fiber–reinforced as well as reinforced with uncoated rebars.
Placement of all bridge deck concrete in Hawaii is done at night
in order to reduce evaporation. This deck placement was unique because
it consisted of more than 1,000 yd3 of concrete placed with no deck
expansion joints. The design strength of the HPC deck was 6000 psi
at 28 days, while approximately 8000 psi was achieved at 28 days.
Preliminary measurements have indicated a 75% reduction in shrinkage
and a 60% reduction in creep. As of this time, no cracks have been
found in the deck of the North-South Road Separation.
The spliced girders consisted of three pretensioned girder segments
that were 40 feet, 80feet, and 40 feet, in length. The segments
were spliced and post-tensioned. These 66-inch girders were modified
Washington State Department of Transportation (WF74PTG) spliced
girders.
The construction of the new multi-lane North-South Road in the
Kapolei area of Oahu will connect Kapolei Parkway to the Interstate
H-1 Freeway. The total project costs are $143 Million, with the
project being constructed in three phases. The third phase, Phase
1C, is the construction of the North-South Road Separation structure
carrying Interstate Route H-1 over the North-South Road ($60 Million),
and is set to be completed in September 2009.
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