the future forward. material properties, such as corrosion resistance, fire resistance and...
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The FutureThe Future
FORWARD
Material properties, such as Material properties, such as
corrosion resistance, fire corrosion resistance, fire
resistance and durability resistance and durability
are being continuously are being continuously
improved and exploited. improved and exploited.
These inherent qualities of These inherent qualities of
precast prestressed precast prestressed
concrete and its concrete and its
considerable design considerable design
flexibility also make it ideal flexibility also make it ideal
for a wide variety of other for a wide variety of other
applications: poles, piles, applications: poles, piles,
culverts, storage tanks, culverts, storage tanks,
retaining walls, sound retaining walls, sound
barriers and even barriers and even
railroad tiesrailroad ties..
THE FUTURE
FORWARDBACK
The benefits of High The benefits of High
Performance Concrete are Performance Concrete are
already beginning to be already beginning to be
applied. These include applied. These include
reduced initial construction reduced initial construction
costs that result from costs that result from
wider girder spacing and wider girder spacing and
longer spans as well as longer spans as well as
reduced long-term costs reduced long-term costs
due to fewer replacements due to fewer replacements
and fewer repairs. High and fewer repairs. High
Performance Concrete is Performance Concrete is
being increasingly being increasingly
specified for the nation’s specified for the nation’s
bridges and structures. bridges and structures.
THE FUTURE
FORWARDBACK
One form of HPC is high One form of HPC is high
strength concrete. A strength concrete. A
strength of 14,000 psi was strength of 14,000 psi was
specified here for the specified here for the
beams of the Louetta beams of the Louetta
Road Bridge, a Road Bridge, a
demonstration project, demonstration project,
located in Houston, Texas. located in Houston, Texas.
High strength concrete High strength concrete
was also used in this was also used in this
bridge for the stay-in-bridge for the stay-in-
place deck panels, the place deck panels, the
cast-in-place concrete cast-in-place concrete
deck and precast deck and precast
segmental piers.segmental piers.
THE FUTURE
FORWARDBACK
The Giles Road Bridge in The Giles Road Bridge in Sarpy County, Nebraska also Sarpy County, Nebraska also was constructed using High was constructed using High Strength Concrete. Strength Concrete. Completed in 1996, it is Completed in 1996, it is another example of a bridge another example of a bridge with 12,000 to 14,000 psi with 12,000 to 14,000 psi concrete girders and a 5,000 concrete girders and a 5,000 to 8,000 psi concrete deck. to 8,000 psi concrete deck. The Federal Highway The Federal Highway Administration, together with Administration, together with PCI and several states, PCI and several states, continues to promote the use continues to promote the use of High Performance of High Performance Concrete in bridge Concrete in bridge applications. For the precast applications. For the precast industry, High Performance industry, High Performance Concrete often involves Concrete often involves higher than average higher than average compressive strength. compressive strength.
THE FUTURE
FORWARDBACK
However, other factors, such However, other factors, such
as low permeability and as low permeability and
resistance to freeze-thaw – resistance to freeze-thaw –
not just strength – may be not just strength – may be
features of High Performance features of High Performance
Concrete depending on the Concrete depending on the
geographic location of the geographic location of the
bridge and the component for bridge and the component for
which it is used. Lightweight which it is used. Lightweight
aggregate concrete with aggregate concrete with
strengths in the 7,000 to strengths in the 7,000 to
10,000 psi range is also being 10,000 psi range is also being
used on some newer bridges. used on some newer bridges.
Lightweight concrete provides Lightweight concrete provides
reduced dead-loads and reduced dead-loads and
seismic forces. seismic forces.
THE FUTURE
FORWARDBACK
Strands of larger diameters Strands of larger diameters and higher strengths are and higher strengths are becoming more common as becoming more common as higher strength concretes higher strength concretes are used and the demand for are used and the demand for higher tensile force higher tensile force increases. When 0.6 inch increases. When 0.6 inch diameter strands are used in diameter strands are used in conjunction with high conjunction with high strength concrete, in the strength concrete, in the 10,000 to 12,000 psi range, 10,000 to 12,000 psi range, standard I-beams and other standard I-beams and other products are able to reach products are able to reach significantly longer spans significantly longer spans never thought possible never thought possible before. Even larger and before. Even larger and stronger strand are on the stronger strand are on the horizon. Corrosion-resistant horizon. Corrosion-resistant steels and coatings promise steels and coatings promise unlimited durability.unlimited durability.
Corrosion-resistant coatingsStainless-cladCorrosion-resistant steel
0.7"?
THE FUTURE
FORWARDBACK
Nonmetallic reinforcement Nonmetallic reinforcement
such as glass, carbon and such as glass, carbon and
aramid fiber composites aramid fiber composites
will be increasingly used will be increasingly used
for special applications. A for special applications. A
recent demonstration recent demonstration
project has shown the project has shown the
compatibility of carbon compatibility of carbon
fiber strands for fiber strands for
prestressing a bridge prestressing a bridge
girder. Both, internally girder. Both, internally
bonded prestressing and bonded prestressing and
external unbonded external unbonded
prestressing systems are prestressing systems are
used.used.
THE FUTURE
FORWARDBACK
Synthetic, organic and Synthetic, organic and
steel fibers have been steel fibers have been
shown to improve shown to improve
toughness and shrinkage toughness and shrinkage
cracking. Recent cracking. Recent
developments in high developments in high
performance fiber-performance fiber-
reinforced concrete hold reinforced concrete hold
promise in terms of promise in terms of
performance and cost-performance and cost-
effectiveness.effectiveness.
THE FUTURE
FORWARDBACK
THE FUTURE
FORWARDBACK
Deg
ree o
f C
orr
osio
n
Time
I
Initiation Propagation(corrosion)
Critical chloride threshold
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
Reinforcing steel corrosionReinforcing steel corrosion
THE FUTURE
FORWARDBACK
Corrosion mechanism Corrosion mechanism of steelof steel
Corrosion Mechanisms Can be Corrosion Mechanisms Can be Minimized By Avoiding Microgalvanic Minimized By Avoiding Microgalvanic
Cell Formation Present in Conventional Cell Formation Present in Conventional and Micro-Alloyed Steelsand Micro-Alloyed Steels
THE FUTURE
FORWARDBACK
MMFX is not a stainless MMFX is not a stainless
steel but Step 1 of its steel but Step 1 of its
production adds production adds
chromium and reduces chromium and reduces
the carbon content.the carbon content.
Benefits of adding Benefits of adding
chromium to reduce the chromium to reduce the
steel’s corrosion rate.steel’s corrosion rate.
THE FUTURE
FORWARDBACK
MMFX approach to MMFX approach to altering the micro-altering the micro-structure of the steel: structure of the steel: Produce a Produce a Microcomposite Steel Microcomposite Steel that Eliminates that Eliminates Formation of Formation of Microstructural Galvanic Microstructural Galvanic CellsCells
~ 0 .1m
Prior Prior AustenitAustenite Grain e Grain BoundarBoundar
yy 2 –2 –Dislocated Dislocated
LathsLaths(Martensit(Martensit
e)e)
1 – Untransformed Nano1 – Untransformed NanoSheets of AusteniteSheets of Austenite
1
2
2
2
2
2
1
1
1
1
The Second Step The Second Step
to Achieving to Achieving
Microstructure Microstructure
SteelSteel
THE FUTURE
FORWARDBACK
Reinforcement
Type
Low
Cost installation
High
Cost installation
Chloride Threshold
(lb/yd3)
Propagation (years)
Black Steel $0.38 $0.53 1 6
Epoxy Coated Steel $0.50 $0.66 1 20
Stainless Steel $2.75 $2.91 20 12
MMFX 2 Steel (4 X) $0.70 $0.85 4 12
MMFX 2 Steel (6 X) $0.70 $0.85 6 12
THE FUTURE
FORWARDBACK
Reinforcement TypeReinforcement Type Installation Installation CostCost
InitialInitialCostCost($/ft($/ft22))
Time to Time to Initiation Initiation (Years)(Years)
Time to Time to First First
RepairRepair(Years)(Years)
Total Life Total Life Cycle Cycle Cost Cost ($/ft($/ft22))
MMFX 2 Steel (4 X)MMFX 2 Steel (4 X) HIGHHIGH $15.01$15.01 9090 >100>100 $15.01$15.01
MMFX 2 Steel (6 X)MMFX 2 Steel (6 X) HIGHHIGH $15.01$15.01 >100>100 >100>100 $15.01$15.01
Epoxy Coated SteelEpoxy Coated Steel HIGHHIGH $14.93$14.93 4444 6464 $19.02$19.02
Black SteelBlack Steel HIGHHIGH $14.42$14.42 4444 5050 $21.31$21.31
Stainless SteelStainless Steel HIGHHIGH $23.75$23.75 >100>100 >100>100 $23.75$23.75
Self Consolidating Self Consolidating
concrete is an extremely concrete is an extremely
cohesive and flowable cohesive and flowable
material capable of being material capable of being
placed without vibration. placed without vibration.
It can be placed very fast It can be placed very fast
at a very dramatic at a very dramatic
reduction in noise.reduction in noise.
THE FUTURE
FORWARDBACK
The cohesion of the fresh The cohesion of the fresh
concrete and no negative concrete and no negative
effects from vibration will effects from vibration will
result in a more result in a more
homogeneous surface homogeneous surface
layer. This reduces layer. This reduces
permeability, increases permeability, increases
resistance to chloride resistance to chloride
ingress, carbonation and ingress, carbonation and
other chemical attackother chemical attack
THE FUTURE
FORWARDBACK
Another development has Another development has been the use of precast deck been the use of precast deck panels. Used as stay-in-place panels. Used as stay-in-place forms, the panels reduce forms, the panels reduce labor for field placement of labor for field placement of reinforcing steel and reinforcing steel and concrete for bridge decks, concrete for bridge decks, resulting in considerable resulting in considerable savings. The panels become savings. The panels become composite with the field-composite with the field-placed concrete for live placed concrete for live loads. They’re made of high-loads. They’re made of high-quality, plant-produced quality, plant-produced concrete and contain the concrete and contain the primary tensile primary tensile reinforcement between reinforcement between beams. They remain crack-beams. They remain crack-free, protecting this free, protecting this important reinforcing steel.important reinforcing steel.
THE FUTURE
FORWARDBACK
Full-depth precast deck Full-depth precast deck
panels promise to provide panels promise to provide
the solution for extended the solution for extended
closings due to deck closings due to deck
replacement. The technique replacement. The technique
applies to new construction applies to new construction
as well. Precast highway as well. Precast highway
paving panels are being paving panels are being
demonstrated in Texas to demonstrated in Texas to
speed lane widenings and speed lane widenings and
reduce traffic closures and reduce traffic closures and
detours. Refined materials detours. Refined materials
and methods are making and methods are making
these solution an exciting these solution an exciting
new part of the designers new part of the designers
tool box.tool box.
THE FUTURE
FORWARDBACK
Another innovation is the Another innovation is the
development of development of
horizontally curved horizontally curved
precast concrete bridges precast concrete bridges
which is creating exciting which is creating exciting
new options in new options in
contemporary bridge contemporary bridge
designs. This technique designs. This technique
involves post-tensioning involves post-tensioning
precast elements together precast elements together
in the plants before in the plants before
shipment or in the field shipment or in the field
after erection.after erection.
THE FUTURE
FORWARDBACK
THE FUTURE
Spliced girders give Prestressed concrete girders the ability to reach further and longer
FORWARDBACK
And yet another solution And yet another solution
for curved structures is for curved structures is
segmental construction. segmental construction.
Working together with the Working together with the
American Segmental American Segmental
Bridge Institute (ASBI) and Bridge Institute (ASBI) and
the AASHTO Bridge the AASHTO Bridge
Subcommittee, PCI has Subcommittee, PCI has
endorsed a family of endorsed a family of
standard shapes for standard shapes for
segmental bridges that is segmental bridges that is
intended to reduce the intended to reduce the
cost of segmental bridges cost of segmental bridges
for smaller structures such for smaller structures such
as urban grade as urban grade
separations. separations.
THE FUTURE
FORWARDBACK
Prestressed concrete got Prestressed concrete got
its start as the original its start as the original
composite material and composite material and
further developments by further developments by
the industry and its the industry and its
suppliers have continued suppliers have continued
to refine the performance to refine the performance
of the product for the of the product for the
bridge market.bridge market.
THE FUTURE
FORWARDBACK
Today, it still gives the Today, it still gives the
public extremely good public extremely good
value for its money. The value for its money. The
reputation of the precast reputation of the precast
prestressed concrete prestressed concrete
industry has been built on industry has been built on
the strength, imagination, the strength, imagination,
consistency and integrity consistency and integrity
of its people and products of its people and products
alike. In the future, it will alike. In the future, it will
continue to be the continue to be the
solution of choice.solution of choice.
THE FUTURE
FORWARDBACK
Thank You for Your
Attention
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