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| Photo courtesy Precast/Prestressed
Concrete Institute |
Roundtable
The
Leaders Speak
As steel and lumber prices rise, we surveyed leaders
of the concrete industry to determine the industry’s
strengths. Here are what these prominent concrete
people have to say about relative costs, new technologies
and potential structural applications for concrete.
Q.
Is concrete benefiting from high prices of other
structural materials?
 Theodore
L. Neff, P.E.,
Executive Director, Post-Tensioning
Institute
A. The dramatic
escalation of steel prices worldwide has certainly
improved concrete’s competitive position
relative to other structural systems in the last
year or so. This advantage has been offset somewhat
by significant increases in the cost of cement
and lumber (for formwork).
Increasing material costs combined with growing
environmental awareness (e.g., LEEDS) has led
many designers to try and optimize their structural
designs to minimize the use of materials. This
has heightened interest in high-strength materials
such as post-tensioning. Using high- strength
prestressing steel with high- performance concrete
is a very efficient use of materials.
 Gerald
F. Voigt, P.E., President and CEO,
American Concrete Pavement Assn.
A. Fundamentally,
we regard concrete as the material of choice for
the construction and rehabilitation of highways,
airfields, and roadways. Although we recognize
the steady increases in the cost of competitive
materials, including asphaltic crude oil, it is
our view that concrete traditionally provides
the best value to taxpayers and agencies, without
regard to price fluctuations in raw materials,
because it simply is more durable and outlasts
other paving materials.
 Monica
Schultes, Mid-Atlantic Precast Association
A. Owners, designers
and estimators are still recovering from the sticker
shock of the past 18 months when the unprecedented
rise of steel prices occurred. The increase in
prices coupled with the volatility and lack of
availability have many owners and designers seeking
alternate solutions. Steel frame structures have
been common across the mid-Atlantic region. This
opportunity has allowed the industry to discuss
non-traditional solutions such as total precast
office structures. The lower initial costs and
the speed of construction contributed to many
projects being redesigned using precast concrete
as a viable alternative.
 James
G. Toscas, President, Precast/Prestressed
Concrete Inst.
A. Concrete
costs have re-mained relatively stable, while
other structural materials—specifically steel—have
experienced sharp price increases. According to
a Bureau of Labor Statistics report, 2004 year-end
steel prices were 48.3% above the previous year.
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| Photo courtesy of the
Precast/Prestressed Concrtete Institute |
In the private sector, continued sticker shock
in the steel marketplace has caused contractors
and developers to pursue other options, particularly
concrete. Nationwide, the industry is reporting
a strong and growing demand for precast concrete
building systems, often as design conversions
from steel. The three-tier engineering approach
used by precast building systems enable them to
emulate, where appropriate, other forms of construction.
Projects in the transportation sector are designed
over a year in advance of letting. Nevertheless,
with rapidly increasing steel prices, we see redesigns
and value engineering change proposals for structures
that were planned in steel. For example, previously
cost-competitive concrete piles now have a distinct
cost advantage relative to steel H sections.
Robert A. Garbini, P.E.,
President, National Ready Mixed Concrete
Association
A. I wouldn’t
say necessarily that concrete is benefiting because
of the high cost of other materials. More than
that is the recognition of the superior performance
capabilities and flexibility of concrete over
other materials.
Q. What
new concrete technologies are changing construction?
 Jim
Cagley, President, American
Concrete Institute
A. Self-consolidating
concrete is having a major impact on the manufacture
of precast/prestressed concrete products. With
careful control of mixture proportion—especially
water content—and the mixing and forming
equipment used, precast manufacturers have been
able to reduce labor, recycle forms faster and
make their operations much more efficient. Here
in the U.S., we’re still developing the most
efficient cast-in-place applications for this
technology and gathering information, such as
expected form pressures, relating to the construction
side. ACI Committee 237, Self-Consolidating Concrete,
submitted an Emerging Technology Series document
on the subject for review by our Technical Activities
Committee in April.
Pervious concrete is a technology that isn’t
new, but is drawing increased interest because
pavements built with pervious concrete are an
effective means for meeting environmental demands
for new construction. These pavements allow rainwater
to seep into the ground and recharge groundwater
rather than creating stormwater runoff. ACI Committee
522 is developing information on pervious concrete.
Robert A. Garbini,
National Ready Mixed Concrete Association
A. The concrete
technologies that are changing construction have
more to do with the additional admixtures that
are coming on the market. Self-consolidating concrete
is an example of how these admixtures can change
construction processes.
James G. Toscas,
Precast/Prestressed Concrete Inst.
A. Recent advances
in materials technology are improving the quality
and design flexibility of concrete structures,
and the precast building systems industry is at
the forefront of their application. High-performance
concrete (HPC) provides high compressive strength,
high density, low permeability and superior chemical
resistance. Precast structures utilizing HPC attain
levels of durability and longevity unheard of
even a few years ago. Self-consolidating concrete
(SCC) is a highly-flowable, non-segregating material
that significantly improves consolidation around
reinforcement and finished surface quality, while
decreasing construction time, labor and equipment.
The precast building systems industry has literally
“written the book” on SCC applications.
Seeing these advantages, four state DOTs have
approved SCC for bridges and others are planning
to do so. The precast building systems industry
has recently introduced “space-age”
composite technologies utilizing new materials
such as carbon fiber and ultra-high performance
concrete (UHPC), providing superior durability
and strength-to-weight performance while enabling
aesthetic design flexibility unmatched by any
other material.
Shrinivas B. Bhide,
S.E., P.E., PhD, Chair,
National Concrete Bridge Council and Bridge Program
Manager, Portland Cement Association
A. To address
the deficient bridge problem, we should build
HPC bridges that offer cost efficiencies, time
savings, and twice the lifespan of conventionally
built bridges. And a foundation of research, development
and “showcase” bridges has established
these findings. However, additional technology
transfer, research and implementation are needed
to ensure the expectations of general public,
industry, and the government can be met. The National
Concrete Bridge Council (NCBC), after extensive
consultation with FHWA and state DOT engineers,
professors and industry representatives has published
a strategic plan for the widespresd implementation
of HPC bridges: Building New Generation of Bridges–A
Strategic Perspective for the Nation.
 Beatrix
Kerkhoff, Program Coordinator,
Cement and Concrete Technology, Portland Cement
Association
A. Self-consolidating
concrete (SCC) is certainly a new technology that
is changing concrete construction. The use of
SCC in North America has grown tremendously since
2000, especially in the precast industry.
SCCis defined as highly flowable, nonsegregating
concrete that can spread into place, fill the
formwork and encapsulate the reinforcement under
its own weight without any mechanical consolidation,
which already indicates its advantages.
Economic benefits include labor savings due to
reduction in manpower required to place the concrete
(no or little vibration needed), time savings
due to accelerated speed of construction, and
fewer equipment and power costs. Technological
benefits include better and uniform filling of
formwork, especially formwork with difficult access
or dense reinforcement, and noise reduction in
urban areas and precast plants due to vibration-free
concrete. In addition, SCC has excellent bond
to reinforcement, good structural performance
and durability as well as a high-quality surface
finish.
Key to SCC is to achieve a high flow rate without
segregation. That requires careful adjustments
to the mixture proportions and careful batching.
Generally, the higher the required flowability
of the SCC mix, the higher the amount of fine
material needed to produce a stable mixture. In
some cases, a viscosity-modifying admixture can
be used instead of, or in combination with, an
increased fine content to stabilize the concrete
mixture.
Gerald F. Voigt, P.E.,
American Concrete Pavement Association
A. A number of technologies and technological
enhancements are impacting construction. Not the
least of these enhancements is our present focus
on improving surface characteristics. More specifically,
the American Concrete Pavement Association is
working closely with agencies of jurisdiction,
a broad cross-section of the concrete pavement
industry and our affiliated chapter/state network
to further enhance concrete pavement surfaces.
Together, we’re focusing on the safety of
the nation’s surface transportation network
and the driving experience for the motoring public.
In addition, we are continuing to develop and
promote other time-tested, well-proven technologies,
including whitetopping (2- to 6-in.) overlays
over asphalt, overlays over existing concrete
pavements and our full range of concrete pavement
rehabilitation (resurfacing, repair and reconstruction)
technologies. The use of precast panels for repairing
facilities also appears to be poised as the next
application breakthrough.
Of course, we also recognize the importance of
providing education and training in leading-edge
technologies to assist contractors and agencies
in construction, which has a profound effect on
opening pavements to public traffic faster than
in the past.
Monica Schultes,
Mid-Atlantic Precast Association
A. Self-consolidating
concrete: This material is widely used
across the precast industry and is valued for
its increased workability and fluidity. The new
mixes allow the concrete to flow quickly into
place and reach every inch of the precast form.
This provides reduced labor in the casting process
as well as improved strength and aesthetics. The
flow ability prevents unconsolidated areas or
bug-holes from marring the surface finsh and ensures
even the most congested forms will be adequately
filled.
3-D parametric modeling:
The use of automated, parametric 3-D modeling/design
software will be used by all segments of the industry
to develop precast concrete structures. 3-D modeling
should reduce costs, improve accuracy and efficiency
and offer better and faster communication. The
program will help design structures as well as
provide information for estimating, manufacturing,
erecting and finishing components. Construction
is a collaborative team effort so every member
of the team will have instant access to all the
information all of the time. As changes are made,
everyone should be able to view those changes.
When fully implemented, the 3-D modeling should
reduce drafting costs by 80%, reduce engineering
costs up to 35% for large projects and 50% for
smaller/more complex projects that are design
intensive.
RFID: While
many precast manufacturers have been utilizing
bar codes and scanners to track product in their
yard, RFID tags devices will enable them to do
much more, from ordering supplies to scheduling
to transportation and installation, as well as
managing assets, getting paid for product in storage
and just-in-time delivery scheduling.
Carbon fiber: Carbon
grid can be used to replace secondary steel reinforcement
in precast concrete. This reduces the weight and
increases corrosion resistance in the components.
Carbon fiber reduces the weight significantly
(more than 60% in a typical architectural wall
panel) and the reduced weight translates into
lower shipping and erection costs as well as foundation
sizing and costs.
Theodore l. Neff, P.E.,
Post-Tensioning Institute
A. In the last
decade, there has been increasing concern among
owners, designers and contractors over the durability,
speed and quality of construction. Many new concrete
technologies have emerged as a result. In the
field of post-tensioning, the advent of encapsulated
anchors for unbonded systems, and improved ducts
and grouting procedures for bonded P-T systems
have resulted in significant improvements in corrosion
resistance and durability of post-tensioned concrete
structures. Innovative formwork systems and construction
techniques have made it possible to construct
concrete structures more quickly and with less
disruption to the public and adjacent facilities.
For example, it is now common to construct post-tensioned
concrete buildings with a 2-to-3-day cycle per
floor. Combining post-tensioning with precast
concrete technology has also had a dramatic impact
on construction, as perhaps best evidenced by
the growing use of segmental bridges.
To improve and assure the quality of concrete
construction, owners and specifiers have become
increasingly reliant on industry certification
programs. For example, the Post-Tensioning Institute’s
Unbonded Tendon Plant Certification program requires
post-tensioning fabricators to institute strict
quality control procedures that go beyond the
requirements of most standard specifications.
PTI’s certification programs for field installers
provide valuable training and assurance that post-tensioning
workers are qualified.
Q.
What is the potential
for concrete work in rehabilitating highways,
bridges and dams?
Fares Y. Abdo, P.E.,
Program Manager, Water Resources, Portland
Cement Association
A. Dams in the
United States are aging and in need of replacement
or repairs. The U.S. Army Corps of Engineers recently
published an updated national inventory of dams,
which includes approximately 79,000 dams. More
than 24,000 of these dams are beyond their effective
design life of 50 years. Twenty years from now,
80% of the dams in the U.S. will be 50 years old
or older. Numerous aging high-hazard dams have
been found inadequate to sustain earthquake loads
or hydrostatic pressures during severe flood events.
Failure of any of these dams could result in loss
of lives and significant property damage.
Roller-compacted concrete (RCC), a relatively
dry concrete material that is spread and compacted
using earth moving, paving and/or conveying equipment,
has been used in dam rehabilitation and in construction
of new dams since the early ‘80s. RCC has
gained recognition in a relatively short period
due to its performance, cost effectiveness and
speed of construction.
Inadequate spillway capacity is one of the major
causes of embankment distress. RCC is proven to
be a cost-effective material used to rehabilitate
these embankments. More than 80 RCC spillway and
overtopping protection projects have been completed
in the U.S. over the past 20 years. Rehabilitating
these dams with RCC essentially consists of making
a portion of the entire dam to function as an
erosion-resistant emergency spillway.
In addition, RCC has been used on numerous projects
to buttress existing dams or to replace dams that
do not meet today’s safety standards. More
than 350 RCC gravity dams have been constructed
worldwide to date, 272 of which are greater than
50 ft high. Examples of dam projects currently
under construction with roller-compacted concrete
include Saluda Dam in South Carolina and Loch
Raven Dam in Maryland.
Jim Cagley,
American Concrete Institute
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| Photo courtesy
of L.M. Scofield |
A. Concrete
will always play a major role in rehabilitating
our infrastructure because much of the infrastructure
was originally constructed with concrete. A primary
requirment for repair materials is that their
properties closely match the properties of the
materials in the structural member being repaired.
We can modify the properties of portland cement
concrete by adding polymers, water-reducing admixtures,
fibers and other materials that improve performance
as a repair material, but the base material is
still concrete, with properties similar to those
of the material being repaired. We also have used
fiber-reinforced polymer products to repair concrete,
either internally in the form of reinforcing bars
or externally as sheets adhered to structural
members.
Robert A. Garbini,
Nat’l Ready Mixed Concrete Assn.
A. The potential is huge. Concrete offers
so many different long-term solutions to our infrastructure
needs.
Gerald F. Voigt, P.E.,
American Concrete Pavement Association
A. We are very
optimistic about the outlook for concrete pavement
rehabilitation of highways, airfields and roadways—the
three markets managed by the American Concrete
Pavement Association. We are, of course, awaiting
passage of the federal-aid highway bill, which
will provide long-awaited funding, not only for
highway construction and rehabilitation, but also
for research and development. It’s important
to note, however, that passage of the bill will
not signal a conclusion or even a temporary cessation
of our advocacy efforts, but only another step
in the push for adequate funding levels.
We will continue to work with other partners
in the transportation-construction industry to
support the highest funding levels possible to
meet the critical needs of the nation’s surface
transportation network. To do anything less would
be to compromise the safety and performance of
the nation’s highways, airfields and roadways.
Funding is only part of the equation. In addition
to advocating for the requisite funding levels,
we will continue to focus on optimizing our product
through research, technological enhancements,
education and training, and outreach to stakeholders
in every quarter. We have made tremendous strides
in all of these areas and will continue to do
so to transcend the misperceptions that result
in wasted taxpayer dollars and application of
inferior paving materials. We are simply not moving
off or away from our goal of returning the highest
value, safety and performance to the traveling
public.
James G. Toscas,
Precast/Prestressed Concrete Inst.
A. An estimated
600,000 roads and bridges are presently scheduled
for repair, at a projected cost approaching $200
billion. Reports from the National Bridge Inventory
indicate as many as 125,000 bridge structures
are in need of attention. With durability, flexibility
and life-cycle cost advantages, concrete is and
will continue to be the dominant material in rehabilitating
highways, bridges and dams.
Precast building systems have a significant additional
advantage in minimizing economic disruption due
to construction. Precast concrete bridges, which
now account for more than 50% of new and replacement
bridge projects, have been erected in as little
as one weekend. Precast bridges enjoy a broad
range of application, with precast segmental bridges
having spanned over 975 ft, and conventional precast
bridges using spliced girder technology spanning
up to 350 ft. Precast pavement and bridge deck
panels can be installed literally overnight to
replace deteriorated pavement sections.
Charles Hawkins,
Executive Vice President, National Stone,
Sand and Gravel Association
A. The potential
is great, as long as the country has a well-funded,
comprehensive federal highway program in place.
We’ve been without one since Sept. 30, 2003,
(when TEA 21 expired). Since then, Congress has
extended the existing program six times and, in
so doing, created havoc with the states’
long-range planning processes. The House passed
its version of a reauthorization bill in March
and the Senate is considering its version now.
The aggregates industry is doing everything it
can to get a bill enacted at the highest funding
level possible and signed by the president. Aggregates
prod-ucers across America will have no trouble
meeting the resulting demand.
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The
Library of Congress National Audio-Visual Conservation
Center in Culpeper, VA, contains, among other
parts, 120 nitrate-film storage vaults. And because
the nitrates in the film can exude flammable vapors
as they deteriorate, the vaults are four-hour
rated to contain combustion.
Contractors
have been using Stay-Form (from AMICO of AL) since
1981 to form bulkheads, primarily due to the significant
labor savings they realize because they do not
have to strip the formwork. The use of rebar,
strongbacks, walers, kickers, etc., (location,
size and spacing) is similar to that for conventional
forming methods. The lightweight sheets (11.9
lb) are easy to cut, bend and install to form
keyways with or without waterstop. Rebar and conduit
penetrations can be made with tin snips or by
pushing a pointed rebar through the Stay-Form
herringbone mesh. Another benefit is the ability
to visually inspect the concrete pour during consolidation
to avoid any honeycombing or bugholes. This cannot
be done with modular or plywood forms. 
In
planning construction of the new William Osler
Health Center in Brampton, Ontario, general contractor
Ellis Don was looking for ways to save time on
a large winter concrete pour. With 600,000 sq
ft of slab to build starting in January 2005,
the contractor brought in Aluma System’s
Hi Flyer column-hung forming system. These units
avoided the need for re-shoring and sped up the
construction by opening the floors to trades or
storage. The project is ahead of schedule, with
a mid-September completion anticipated.
The
safety of site personnel is the highest priority
for all those in charge of site operations. Furthermore,
experience shows that if site personnel are able
to work under safe conditions, productivity increases.
This fact has led PERI’s engineers to develop
a wide range of safety features such as the new
PERI CPP–Climbing Protection Panel. The top
three floors are always completely enclosed by
climbable protection panels. The solid, plywood
face prevents falling debris and gives reliable
prot-ection against wind and harsh weather conditions.
The climbing protection panel is permanently and
safely connected (even during climbing operations)
at the front of the slabs by means of climbing
rails and shoes. Climbing takes place in cost-effective
units which are matched to the allowable crane
capacity. All work on the external facade can
then follow quickly, which accelerates the entire
construction progress. 
In
Long Beach, CA, the builder constructing two 18-story
condominium towers with seismic sensitivity chose
tunnelforming to move the job along while getting
strong reinforced structures.
The
Symons Alisply™ system is a high-strength
concrete forming system designed for fast-paced
gangform operations.
Long
involved in the heavy civil construction arena,
EFCO is an experienced player in horizontal and
vertical forming solutions in commercial building
and high-rise applications. Contractors wanting
higher forming productivity and lower demands
on their valuable crane time understand the benefits
of self-climbing formwork, and often choose these
systems for efficient construction of mid to high-rise
commercial and residential buildings.
Use
of the Alkus plastic composite panel instead of
plywood is said by Meva Formwork Systems to produce
consistently smooth and nearly bubble-free concrete
finishes for hundreds of reuses
“Guys
with relatively no computer experience at all
are now sending daily time card data via e-mails
instead of driving long distances to deliver paper
time sheets back to our main office,” says
Jeff Fuerst, operations manager at P.J. Hoerr
Inc. “In addition to being easy to use for
anyone, the thing we like best about HeavyJob
is the ‘instant feedback’ we get for
all of our projects,” he continued. (HeavyJob
is a copyrighted product of HCSS.) The benefit
of this kind of daily reporting is clear. Problems
can be spotted in a timely manner and fixed. With
P.J. Hoerr’s old method of job tracking,
it would take two or three weeks to get the cost
information needed for job analysis back from
accounting to realize there was a problem.
Able
to turn 360 degrees within its own length, the
Gomaco 9500 trimmer is claimed to be the most
versatile machine of its kind. A front-mounted
trimmer makes it easy for the operator to pass
within inches of obstacles. The rear conveyor
has 160-degree swing and a discharge height up
to 16 ft.
For
nearly 40 years, MC2 has pioneered the use of
computers in construction cost estimating. The
latest product, ICE 2000, is a comprehensive solution
to the estimating problems of contractors of all
sizes and types. ICE 2000 builds on industry-specific
Knowledge Bases that address commercial, industrial
and residential construction. The basic system
features include user-defined work breakdown codes
that can represent alternates, components, systems,
or any of 35 different categories that each user
can specify; an easy-to-use report designer; labor
pricing based on crews, trade man-hours, unit
prices, or any combination; powerful take-off
tools and conceptual estimating tools; and interfaces
to trade pricing services. Just recently, MC2
added a new feature called Capture Desktop, a
unique functionality that allows estimators to
accurately and precisely perform virtual take-offs
from digital plans—and even e-mail the entire
drawing in a simple .jpg format. Other enhancements
include spec-driven take-off for industrial piping
and new interfaces to accounting and scheduling
software and a new bid day function. 
A
geometric plate dowel basket is available for
owners to build better and cheaper floors. PNA’s
PD3 Basket™ Assembly is engineered for use
in a “strategic reinforcement” floor
design enabling engineers to optimize steel and
provide the economical, maintenance-free floors
owners demand.
A
newly engineered blend of synthetic fibers, called
Novomesh® 950, prov-ides an alternative secondary
concrete reinforcement when steel products can’t
be used. SI® Concrete Systems is the producer.
Behind
Big Projects Are The Materials
Concrete
Resurfacing
The
Skyway element of the SFOBB is composed of cast-in-place
vertical elements and precast box girders/decks.
The precast section is being completed in segments
using travelers. According to Boyd Kelly of Regional
Steel Corp. (RPS), the rebar supplier on the project,
“Each segment is like building an entire
structure. The bridge deck is 87 ft wide. The
segments coming off a pier table weigh in excess
of 800 tons each. This is one of the largest precast
segments ever built.”
DYK
Inc. recently conducted a jobsite tour of the
8-million-gallon externally machine-strandwrapped
prestressed concrete tank being constructed for
the city of Foster City, CA. Since the tank is
located adjacent to the San Francisco Bay, an
aggressive marine environment, a prestressed concrete
tank was determined to be the most cost-effective
option because it would not involve expensive
re-coating in the future. Another design consideration
addressed the potential for large seismic forces
in the area. The project team included Brown and
Caldwell, consulting engineer, and Proven Management
Inc., general contractor. 