The Future

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The Future
FORWARD
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THE FUTURE

• Material properties, such as corrosion
  resistance, fire resistance and durability are
  being continuously improved and exploited.
• These inherent qualities of precast prestressed
  concrete and its considerable design flexibility
  also make it ideal for a wide variety of other
  applications poles, piles, culverts, storage
  tanks, retaining walls, sound barriers and even
  railroad ties.

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THE FUTURE

• The benefits of High Performance Concrete are
  already beginning to be applied. These include
  reduced initial construction costs that result
  from wider girder spacing and longer spans as
  well as reduced long-term costs due to fewer
  replacements and fewer repairs. High Performance
  Concrete is being increasingly specified for the
  nations bridges and structures.

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THE FUTURE

• One form of HPC is high strength concrete. A
  strength of 14,000 psi was specified here for the
  beams of the Louetta Road Bridge, a demonstration
  project, located in Houston, Texas. High strength
  concrete was also used in this bridge for the
  stay-in-place deck panels, the cast-in-place
  concrete deck and precast segmental piers.

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THE FUTURE

• The Giles Road Bridge in Sarpy County, Nebraska
  also was constructed using High Strength
  Concrete. Completed in 1996, it is another
  example of a bridge with 12,000 to 14,000 psi
  concrete girders and a 5,000 to 8,000 psi
  concrete deck. The Federal Highway
  Administration, together with PCI and several
  states, continues to promote the use of High
  Performance Concrete in bridge applications. For
  the precast industry, High Performance Concrete
  often involves higher than average compressive
  strength.

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THE FUTURE

• However, other factors, such as low permeability
  and resistance to freeze-thaw not just strength
  may be features of High Performance Concrete
  depending on the geographic location of the
  bridge and the component for which it is used.
  Lightweight aggregate concrete with strengths in
  the 7,000 to 10,000 psi range is also being used
  on some newer bridges. Lightweight concrete
  provides reduced dead-loads and seismic forces.

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THE FUTURE

• Strands of larger diameters and higher strengths
  are becoming more common as higher strength
  concretes are used and the demand for higher
  tensile force increases. When 0.6 inch diameter
  strands are used in conjunction with high
  strength concrete, in the 10,000 to 12,000 psi
  range, standard I-beams and other products are
  able to reach significantly longer spans never
  thought possible before. Even larger and stronger
  strand are on the horizon. Corrosion-resistant
  steels and coatings promise unlimited durability.

Corrosion-resistant coatings Stainless-clad Corros
ion-resistant steel
0.7"?
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THE FUTURE

• Nonmetallic reinforcement such as glass, carbon
  and aramid fiber composites will be increasingly
  used for special applications. A recent
  demonstration project has shown the compatibility
  of carbon fiber strands for prestressing a bridge
  girder. Both, internally bonded prestressing and
  external unbonded prestressing systems are used.

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THE FUTURE

• Synthetic, organic and steel fibers have been
  shown to improve toughness and shrinkage
  cracking. Recent developments in high
  performance fiber-reinforced concrete hold
  promise in terms of performance and
  cost-effectiveness.

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THE FUTURE

• Reinforcing steel corrosion

Migration of chlorides, H20 and O2 into the
concrete, no corrosion and no damage to concrete
Corrosion of the steel reinforcement and cracking
and/or spalling of concrete
Initiation
Propagation (corrosion)
Degree of Corrosion
Critical chloride threshold
I
Time
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THE FUTURE
Corrosion mechanism of steel
Corrosion Mechanisms Can be Minimized By Avoiding
Microgalvanic Cell Formation Present in
Conventional and Micro-Alloyed Steels
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THE FUTURE
MMFX is not a stainless steel but Step 1 of its
production adds chromium and reduces the carbon
content. Benefits of adding chromium to reduce
the steels corrosion rate.
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THE FUTURE
The Second Step to Achieving Microstructure Steel
MMFX approach to altering the micro-structure of
the steel Produce a Microcomposite Steel that
Eliminates Formation of Microstructural Galvanic
Cells
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THE FUTURE
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THE FUTURE
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THE FUTURE

• Self Consolidating concrete is an extremely
  cohesive and flowable material capable of being
  placed without vibration. It can be placed very
  fast at a very dramatic reduction in noise.

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THE FUTURE

• The cohesion of the fresh concrete and no
  negative effects from vibration will result in a
  more homogeneous surface layer. This reduces
  permeability, increases resistance to chloride
  ingress, carbonation and other chemical attack

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THE FUTURE

• Another development has been the use of precast
  deck panels. Used as stay-in-place forms, the
  panels reduce labor for field placement of
  reinforcing steel and concrete for bridge decks,
  resulting in considerable savings. The panels
  become composite with the field-placed concrete
  for live loads. Theyre made of high-quality,
  plant-produced concrete and contain the primary
  tensile reinforcement between beams. They remain
  crack-free, protecting this important reinforcing
  steel.

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THE FUTURE

• Full-depth precast deck panels promise to provide
  the solution for extended closings due to deck
  replacement. The technique applies to new
  construction as well. Precast highway paving
  panels are being demonstrated in Texas to speed
  lane widenings and reduce traffic closures and
  detours. Refined materials and methods are making
  these solution an exciting new part of the
  designers tool box.

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THE FUTURE

• Another innovation is the development of
  horizontally curved precast concrete bridges
  which is creating exciting new options in
  contemporary bridge designs. This technique
  involves post-tensioning precast elements
  together in the plants before shipment or in the
  field after erection.

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THE FUTURE
Spliced girders give Prestressed concrete girders
the ability to reach further and longer
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THE FUTURE

• And yet another solution for curved structures is
  segmental construction. Working together with the
  American Segmental Bridge Institute (ASBI) and
  the AASHTO Bridge Subcommittee, PCI has endorsed
  a family of standard shapes for segmental bridges
  that is intended to reduce the cost of segmental
  bridges for smaller structures such as urban
  grade separations.

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THE FUTURE

• Prestressed concrete got its start as the
  original composite material and further
  developments by the industry and its suppliers
  have continued to refine the performance of the
  product for the bridge market.

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THE FUTURE

• Today, it still gives the public extremely good
  value for its money. The reputation of the
  precast prestressed concrete industry has been
  built on the strength, imagination, consistency
  and integrity of its people and products alike.
  In the future, it will continue to be the
  solution of choice.

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Thank You for Your Attention
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