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Road Science
High-Performance Concrete Pavements Come of Age
FHWA-supported new research, field applications, and
tech transfer blaze way for durable PCC pavement mixes.
by
Tom Kuennen, Contributing Editor
Early in the new millennium, high-performance
concrete pavements have come of age in the United States.
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High-performance concrete has been supported for
bridge applications since the early 1990s, but HPC no longer is limited
to precast beams or segments, and increasingly is applied to pavements. |
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Since 1996, the Federal Highway Administration’s
TE-30 program — High-Performance Concrete Pavements — has been tracking
25 HPC pavements with different designs and particulars. While a
progress report was produced in 2002, monitoring will continue as late
as 2007 for some projects. |
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Construction of HPC pavements is being
undertaken at the state DOT level, and experiences are being shared. |
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Beginning in 2004, experience with HPC pavements
will be disseminated in a massive new portland cement concrete
technology transfer program by the FHWA. The Concrete Pavement
Technology Program consists of research, product development, and
technology delivery that will improve the performance and
cost-effectiveness of concrete pavements (see related sidebar). |
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Precast panels made of HPC also are making their
way into pavements and airfields, especially where time of construction
is of the essence. |
About high-performance concrete
 HPC is often called durable concrete because its
strength and impermeability to chloride penetration makes it last much
longer than conventional PCC. The concrete mix is engineered with the
typical elements of water, portland cement, and fine and coarse aggregates,
but with admixtures which enhance performance.
“High-performance concrete is not just about
high-strength mixes, but also enhanced durability,” said Leif Wathne, P.E.,
contract FHWA concrete pavement engineer with the FHWA’s Mobile Concrete
Lab, which travels to different venues conducting technology transfer and
test procedure training. “We want a long-life pavement for whatever
environment we’re in, be it New England or Arizona.”
But preparation is needed for an agency seeking to
place HPC pavements, and there’s more to HPC than a mix design, Wathne told
Better Roads editors. “Engineers must do their homework up front, to find
what it is they want from the mix. They then must pick the materials to
accomplish their goals and build the pavement in a manner consistent with
good construction practices.”
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The Federal Highway
Administration's Mobile Concrete Lab on the I-90 project in
Wisconsin in 2002. |
Mobile Concrete Lab
at 3rd International Symposium on High Performance Concrete/PCI
National Bridge Conference in September 2003. |
HPC mix designs were developed in the 1980s in the
private sector to protect parking structures and reinforced concrete
high-rise buildings from chlorides, sulfates, alkali-silica reactivity and
to quell concrete shrinkage and creep.
In HPC, materials and admixtures are carefully
selected and proportioned (optimized) to form high early strengths, high
ultimate strengths and high durability beyond conventional concrete.
Some industrial waste materials of a few decades ago
now are integral elements of this new engineered concrete. These admixtures,
such as coal fly ash, silica fume, and ground granulated blast furnace slag,
add both strength and durability to the concrete, and enhance its
marketability as an environmentally friendly product (see
Reclaimed Byproducts Boost Concrete
Performance, January 2004, Better Roads, p 50).
Providentially, these materials also produce a lower
heat of hydration, which can minimize shrinkage cracking produced by higher
temperatures. Minimizing shrinkage cracks can limit ingress of chlorides.
HPC provides enhanced mechanical properties in
precast concrete structural elements, including higher tensile and
compressive strengths, and heightened modulus of elasticity (stiffness). In
frost-prone regions the benefits of HPC are great. The enhanced durability
of HPC helps it resist penetration of chloride-laden snow and ice melt
water. This results in longer life for the reinforcing steel within, and a
reduction in spalling, cracking, and associated repairs.
The proportions in which fundamental components are
mixed, and the admixtures that are used, constitute the main difference
between conventional PCC and HPC. A high-range water reducing admixture may
provide a required low water/cement ratio, perhaps as low as 0:35.
“As ready mix producers we are called on to provide
mixes with very high-strength, high-modulus elasticity requirements,” said
Hardy Johnson, president, Titan America-Florida Business Tarmac America, and
2004 chairman of the National Ready Mixed Concrete Association. “HPC is the
wave of the future, with higher and higher strengths.”
Today’s state DOT QA/QC programs are putting the
burden of testing premium mixes like HPC on the producers, Johnson told
Better Roads editors. “More and more state highway departments are backing
away from their testing programs of the past, and putting more demands on
the contractors that they be responsible for mix acceptance.” One way of
easing that burden, he said, is for states to require plant certification as
a prequalification, which is one of NRMCA’s goals.
HPC pavements in spotlight
HPC for pavements originated in the Strategic
Highway Research Program (1987-1993), when the mechanical properties of HPC
were described and studied under actual use conditions. SHRP developed a
definition of HPC and funding for limited field trials, which were to be
followed by a substantial implementation period.
In 1993, the FHWA initiated a national program to
encourage use of HPC in bridges. The program included the construction of
demonstration bridges in each of the FHWA regions, and dissemination of the
technology and results at showcase workshops.
 At about the same time, PCC pavement technology
scanning tours visited European countries in 1992 and 1993, and gathered
information on designs that would make its way into U.S. HPC pavement
rationale. The reports from these tours are available online (see For More
Information sidebar elsewhere in this article).
The first HPC pavement application was a widely
publicized, mile-long concrete test section on the Chrysler Expressway in
Detroit (1993), in which techniques such as Belgian surface texturing, a
modified German cross-section, and an Austrian exposed aggregate surface
treatment were used.
Later, HPC pavements got a great boost in 1999, when
the FHWA launched a $30-million research initiative, which would be
leveraged to higher amounts with private sector participation.
Then, just under way, the recently expired
Transportation Equity Act for the 21st Century included $5 million per year
for applied research in rigid (PCC) paving. This resulted in $30 million
over six years to utilize and improve concrete pavement design and
construction practices.
With its HPC initiative, the FHWA articulated its
goal of providing the public with safe, smooth, quiet, long-lasting,
environmentally sound, and cost-effective concrete pavements. Performance
goals for HPC pavements include an increase in pavement system service life,
a decrease in construction time (including fast-track concrete paving
techniques), longer life cycles such as a 30- to 50-year life, and lower
maintenance costs.
“We’re excited about high-performance concrete,”
said Suneel Vanikar, P.E., FHWA’s concrete team leader, Office of Pavement
Technology, in 1999. “The future for HPC pavements is indeed very bright.
“This is a golden opportunity,” Vanikar said. “For
the first time in concrete paving, we will have a joint program between the
public and private sectors. It will be a win-win situation. We want to make
high-performance concrete paving not just a special activity, but a standard
construction practice.”
In this regard, the promotion of HPC pavements
mirrors the effort toward more durable hot-mix asphalt mix designs. The
asphalt industry’s Superpave and stone matrix asphalt mix designs and its
HMA perpetual pavements initiative are aimed at engineering long-life HMA
pavements.
Field projects bear fruit
 Ultimately, this effort resulted in the FHWA’s
High-Performance Concrete Pavements (TE-30) study. TE-30’s initial goal is
to construct highway projects that would apply HPC’s innovative design and
construction concepts. TE-30 has been an active FHWA project since 1996.
Projects address increased service life, reduced time for construction,
lower life-cycle costs, reduced maintenance costs, ultra-smooth-ride
quality, use of recycled or waste products while maintaining quality, or
utilizing innovative construction equipment or procedures.
Projects described in the March 2002 T-30 report
have been constructed in Illinois, Indiana, Iowa, Kansas, Maryland, Michigan
(I-75 Chrysler Freeway), Minnesota, Mississippi, Missouri, New Hampshire,
Ohio, South Dakota, Virginia, and Wisconsin. An additional 14 project
reports will be produced in 2004-2006.
At press time the FHWA was updating the March 2002
report and the product should be available this summer.
New concrete outreach
In spring 2004, current and future T-30 technology
transfer will benefit from the launch of the FHWA’s Concrete Pavement
Technology Program. HPC pavement technology will be a major — but not the
only — element of this exhaustive outreach.
“[CPTP] focuses exclusively on improved quality in
concrete pavements that was addressed in [TEA-21] legislation,” said Sam
Tyson, contract P.E., concrete pavement engineer, FHWA Office of Pavement
Technology.
The transfer of PCC technology through CPTP is being
undertaken by a private sector contractor, the famous Construction
Technology Laboratories, Inc. in Skokie, Illinois, and includes a
subcontractor to facilitate external outreach.
“We are getting information from the projects
transferred to the contractor, so it can work with us to prepare status
reports for all the projects and products,” Tyson said. “Then, a marketing
plan will follow, which will be used to deploy the technology transfer to
our partners and customers throughout the U.S.,” Tyson said.
Tyson told Better Roads editors that there are more
than 30 concrete portland cement concrete research projects, each of which
will yield one or more products for consideration by state DOTs or paving
contractors. “Task 65 will get this technology out to the field,” Tyson
said.
A complete list of ongoing CPTP projects will be
found at
www.fhwa.dot.gov/pavement/cptpindx.htm.
States active in HPC pavements
 The enthusiasm for HPC pavements is not limited to
the federal arena, but is being undertaken by states as well. Last year, the
Ohio DOT applied an HPC pavement mix — promulgated by Dr. Celik Ozyildirim
in Virginia — to the reconstruction of U.S. Route 33 in Nelsonville, Ohio.
Three test sections, each consisting of 1,000 feet, were constructed.
In each test section, 500 feet was to be cured with
membranes; the other 500 feet was to be cured with burlap. Temperature
profile during curing was to be monitored with thermocouples, as was
temperature as a function of time for the maturity test, shape of the slab
with dipstick and stationary profilers, shape of the slab using Ohio DOT
profilers, joint movement of the slabs, and deflection during
non-destructive testing.
That HPC pavements are performing well in Virginia
was reported by Dr. Celik Ozyildirim, Ph.D., principal research scientist,
Virginia Transportation Research Council, in his 2001 TRB paper, Evaluation
of High-Performance Concrete Pavement in Newport News, Virginia.
“Moisture and temperature variations cause
volumetric changes that can lead to cracking and premature failure [in PCC
pavements],” Ozyildirim said. “In jointed pavements, the volumetric changes
caused by friction between the concrete and the base can lead to transverse
cracks that can adversely affect load transfer and carrying capacity.”
The need to reduce shrinkage and increase flexural
strength is consistent with the FHWA’s high-performance concrete pavement
program, he said. “HPCs have enhanced specific properties, such as
workability, durability, strength, and dimensional stability,” Ozyildirim
says. “Increases in maximum aggregate size are expected to necessitate
concretes with less paste, less cementitious material, and less water,
resulting in reduced shrinkage, and to provide better interlock when cracks
occur. Such pavements are expected to be cost-effective because of extended
service life with minimal maintenance.”
In Newport News, the main goal was to reduce the
shrinkage and improve the flexural strength of the concrete by HPC design.
Two of the mixtures contained ground-granulated
blast furnace slag; one had a 50-mm nominal maximum size aggregate, and the
other had a 25-mm NMS aggregate. The third mixture contained Class F fly ash
with a 25-mm NMS aggregate. The contractor, the concrete producer, the FHWA,
and the Virginia DOT worked closely to place the test sections.
“Test results indicated that all three mixtures can
provide satisfactory strength, low permeability, and dimensional stability,”
Ozyildirim said. “The test sections are in excellent condition after two
years of service in the westbound lane and six months of service in the
eastbound lane.”
Illinois: HPC vs. perpetual pavements
In October 2002, the Illinois DOT finished a 10-mile
reconstruction of I-70 in Clark County, which will serve as a comparison to
a hot-mix asphalt perpetual pavement constructed on I-70 in Clark County in
2003 (see Perpetual Pavement, Two Years Later, March 2004).
The Illinois DOT specified an extended life, 30-year
continuously reinforced concrete pavement with high-performance concrete.
The Illinois DOT’s effort to develop a 30-year concrete pavement design had
begun in 1997 and was then bolstered by state legislation passed in 1999.
The legislation provided for a demonstration project that would include the
awarding of 10 contracts utilizing pavements designed for a 30-year life
cycle. The I-70 reconstruction was the first contract awarded under the
demonstration project.
This was a 13-inch CRCP with a 6-inch bituminous
base course on 12 inches of aggregate subbase. Aggregate used was
freeze-thaw resistant, and all tie bars and longitudinal bars had to be
epoxy coated.
Lithium mitigation of ASR
Another feature of HPC pavement mix designs is their
resistance to alkali-silica reactivity. ASR occurs between alkalis from
cement, and a reactive form of silica from the wrong aggregates, which can
result in an alkali/silica gel. If there is enough moisture, the gel will
expand, damaging the concrete.
ASR long has been thought to afflict mainly Western
states, yet Strategic Highway Research Program publication, C-343
Eliminating or Minimizing Alkali-Silica Reactivity, says “the potential for
deleterious ASR in highway concrete exists in every state.”
ASR can be fought through use of non-reactive
aggregates, low-alkali cement, and the addition of fly ash (see Class F Fly
Ash Can Fight ASR, January 2004, Better Roads, p 52), but new research
released last summer shows lithium admixtures are very effective in quelling
ASR. As such they are an important tool for designing HPC pavements when the
potential for ASR may be suspected.
Released in July 2003, Guidelines for the Use of
Lithium to Mitigate or Prevent Alkali-Silica Reaction details ASR and its
mechanisms, symptoms of ASR damage in field structures, ways to mitigate,
test methods, and specifications. Field applications of lithium compounds
are described, and information on treating structures already showing signs
of ASR distress is provided.
Guidelines (FHWA-RD-03-047) may be downloaded from
the Web site of FHWA’s Turner-Fairbank Highway Research Center, at
www.tfhrc.gov/pavement/pccp/pubs/03047.
HPC precast pavements
Prestressed precast concrete panels are feasible for
pavement construction, and at least one such system (the SUPER-SLAB) is
being marketed by the Fort Miller Group.
A breakthrough in application of HPC precast
pavement slabs took place in Texas, where in March 2000, the Center for
Transportation Research (CTR) at the University of Texas-Austin completed an
FHWA-sponsored feasibility study exploring use of precast concrete panels to
expedite construction of PCC pavements.
A 2002 pilot project on the northbound frontage road
of I-35 near Georgetown, Texas, applied the proposed precast pavement
concept. It entailed the construction of 2,300 feet of precast pavement on
either side of a new bridge.
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"Map" cracking -- here highlighted by
moisture in cracts -- is a clue to ASR damaged pavements. |
“Precast concrete panels can be cast and cured in a
controlled environment, stockpiled, and set in place in a short amount of
time, allowing for construction to take place during overnight or weekend
operations,” wrote David K. Merritt and B. Frank McCullough, Center for
Transportation Research, and Ned H. Burns, University of Texas-Austin, in
Development of a Precast Prestressed Concrete Pavement Near Georgetown,
Texas, presented at the 2003 Transportation Research Board meeting.
The project incorporated prestressed panels as a
means of reducing the required thickness of the pavement and to tie the
precast panels together.
Roughness and pavement noise can be problems with
slipformed concrete pavements, and may be worse with precast panel
pavements, and the authors address this issue. “It is believed that a smooth
enough riding surface can be attained with full-depth panels and occasional
diamond grinding, if needed,” they write.
Base preparation is extremely important, so panels
may be placed without delay on a flat surface and are fully supported. They
add the method for ensuring vertical alignment of adjacent panels is
critical, so ridges are not created at the panels’ joints, thereby degrading
ride quality.
They say new research indicates it’s possible to
place a thin (25-50 mm) asphalt leveling course smooth enough and flat
enough that the panels can be placed directly over the leveling course. This
also permits traffic onto the leveling course prior to panel placement.
The mix design used for the precast pavement panels
is a mix similar to that used for precast prestressed bridge beams. The mix
was a seven-sack (Type III) mix with a water-cement ratio of 0:42, and
superplasticizer for increased workability.
A mix of this nature, which is not typically used
for pavements, was necessary to develop sufficient strength for release of
prestress and removal from the forms the following day. The specifications
for the precast panels required that the concrete reach a minimum
compressive strength of 3,500 psi at release of prestress, and a 28-day
compressive strength of 5,000 psi.
Precast slabs in Michigan
Michigan installed precast pavement slabs at the
same time the Georgetown, Texas project took place, not as new main-line
pavement, but as full-depth concrete repairs.
“The use of precast panels eliminates the time
required for curing, as well as offering numerous other benefits such as:
excellent quality of concrete (strength and durability), minimal variability
in slab thickness, and minimal negative impacts from built-in curl,” said
Neeraj Buch, Michigan State University, Vernon Barnhart, Michigan DOT, and
Rahul Kowli, MSU, in their 2003 TRB paper, Pre-Cast Concrete Slabs as
Full-Depth Repairs.
In October 2001 and summer 2002, MSU — in
cooperation with the Michigan DOT — installed 21 precast full-depth patches
along I-94 BL (Benton Harbor) and I-196 (South Haven), in southwestern
Michigan.
The use of precast PCC panels has the potential to
address the key issues of urban pavement renewal such as minimized
construction time and reduced user-delay costs, and enhanced long-term
pavement performance, they say.
That’s because use of precast PCC panels eliminates
the time for PCC curing, as well as offering numerous other benefits,
including excellent quality concrete batched in factory conditions, with
high strength, low shrinkage, and superior durability; control of built-in
curling, with no slabs with excessive built-in curling; and greatly reduced
construction variability, including uniform thickness and material quality.
When user costs are figured in — as required on
major projects by federal law when federal funds are involved — the
economics of precast slabs for full-depth repairs become even more
compelling, they say.
CPTP: New Tech Transfer Program Brings Focus to
PCC
New in 2004, the FHWA’s Concrete Pavement Technology
Program — launched this spring — will bring concrete pavement technology
closer to home. While not limited to HPC pavements, the CPTP products touch
on every aspect of portland cement concrete paving, mix design, and
construction.
The program will be administered by Construction
Technology Laboratories, Inc., Skokie, Illinois. Coming to an office near
you will be results of ongoing and completed research, in the topics listed
below. For more information on the status of each project, visit
www.fhwa.dot.gov/pavement/cptpindx.htm.
The topics include:
Accelerated Load Testing of Ultra-Thin
Whitetopping.
Accelerated Loading Tests of Ultra-Thin
Whitetopping.
AURORA 2000 Pavement System Analysis Tools.
Communication Services for the Concrete Pavement
Technology Program.
Computer-Based Guidelines for Concrete Pavements
(HIPERPAV II).
Computer-Based Guidelines for Job-Specific
Optimization of Paving Concrete.
Concrete Mixture Optimization Using Statistical
Mixture Methods.
Curing of Portland Cement Concrete Pavements.
Develop a Plan to Investigate the Impacts of
Pavement Cracking on Long-Term Performance.
Development of Alkali-Silica Reactivity
Mix-Specific Test Method.
Development of Standard Test for Concrete
Coefficient of Thermal Expansion.
Determine Actual Life Cycle Costs.
Evaluation of Initial PCC Performance-Related
Specification Systems.
Evaluation of the Workability Test and the
Workability of Concrete Paving Mixtures.
Field Trials of Concrete Pavement Product and
Process Technology.
Freeze-Thaw Durability of Concrete with Marginal
Entrained Air Content.
High-Performance Concrete Pavements (TE-30).
Impact of Texturing and Surface Treatment on
Reducing Wet-Weather Accidents.
Incremental Costs and Performance Benefits of
Various Features of Concrete Pavements.
Influence of Sealing Transverse Contraction
Joints on the Performance of Concrete Pavement.
Inertial Profile Data for PCC Pavement
Performance Evaluation.
Long-Term Plan for Concrete Pavement Research
and Technology.
Mobile Concrete Laboratory.
Nondestructive and Innovative Testing Workshop.
PCCP Laboratory Studies.
Performance and Design of Separated (Unbonded)
Concrete Overlays.
Performance and Design of Whitetopping Overlays
for Heavily-Trafficked Pavements.
Potential Adverse Effects of High-Smoothness
Specifications on Concrete Pavement Performance.
Quality Concrete Rehabilitation and Preservation
(SP-205).
Repair and Rehabilitation of Concrete Pavements.
Revision of I-Slab 2000 for Subbase/Pavement
Interaction.
Smoothness Criteria for Concrete Pavements.
Subbase Design.
Technology Transfer, Deployment and Delivery for
the Concrete Pavement Technology Program.
Tests or Standards to Identify Compatible
Combinations of Individually Acceptable Concrete Materials.
Traffic Management Optimization Pilot Studies
for Reconstructing Urban Freeways.
The Use of Precast Concrete Panels to Expedite
Highway Pavement Construction.
The Use of Precast Concrete Panels to Expedite
Highway Pavement Construction — Phase 2: Pilot Studies.
The Use of Precast Concrete Panels to Expedite
Highway Pavement Construction — Phase 3: Demonstration Projects.
Variation of Shrinkage Potential of Portland
Cement Concrete.
Workshops on Concrete Pavement Technology for
State DOT Pavement Engineers.
FHWA/ACI Concrete
Durability Workshops Address Engineering
You can build concrete pavements that last longer
and perform better by learning from the FHWA and American Concrete
Institute’s Concrete Durability Workshop. The movable, two-day workshop
covers the causes, identification, and prevention of common concrete
distresses, including alkali-silica reactivity, freeze-thaw deterioration,
and corrosion of reinforcing steel. The workshop has been presented in at
least 13 states.
This intensive program is intended for designers,
specification writers, materials engineers, contractors, materials
suppliers, and other project personnel, and includes new technologies and
materials, petrography, identification and causes of deterioration,
aggregate source evaluation, designing and specifying durable concrete, ASR
mitigation, alkali-carbonate reactivity, field distress surveys, and much
more.
The FHWA and ACI provide the instructors and course
materials at no cost to the host highway agency, while the host state
supplies the meeting space and audiovisual equipment. To schedule the course
or for more information, contact Gary Crawford at the FHWA, 202-366-1286,
email:
gary.crawford@fhwa.dot.gov); or Jon Mullarky at the FHWA, 202-366-6606,
email: jon.mullarky@fhwa.dot.gov).
For More Information
More information about high-performance concrete
pavements is available by downloading or ordering the following
publications.
The FHWA’s two noteworthy documents on
high-performance concrete pavements are High Performing Concrete Pavements:
Project Summary (FHWA-IF-02-026), describing the 25 TE-30 projects in
detail; and High-Performance Concrete Pavement: Pavement Texturing and
Tire-Pavement Noise (FHWA-IF-02-020). They are available only in hard copy
format; to obtain, call the FHWA’s report center at 301-577-0818. An updated
version of the project summaries will be released in summer 2004.
Much of today’s emphasis in the U.S. on HPC
pavements derives from two scanning tours of European PCC pavement
technology. The 1993 summary report of the second European PCC scanning tour
— U.S. Tour of European Concrete Highways, Follow-Up Tour of Germany and
Austria — may be downloaded at
http://international.fhwa.dot.gov/Pdfs/EuroTour93.pdf.
The 1992 tour which preceded it — to France,
Germany, Austria, the Netherlands, and Belgium — also produced a summary
report. Download it at
http://international.fhwa.dot.gov/Pdfs/eurotour92/eurotour92-1.pdf.
Fly ash can be an important component of HPC
pavement concrete mix. The updated, seminal brochure, Fly Ash Facts for
Highway Engineers, may be downloaded in .html or .pdf formats at
wwwcf.fhwa.dot.gov/pavement/fatoc.htm.
Guidelines for the Use of Lithium to Mitigate or
Prevent Alkali-Silica Reaction, FHWA-RD-03-047 (July 2003), may be
downloaded from the Web site of the FHWA’s Turner-Fairbank Highway Research
Center, at
www.tfhrc.gov/pavement/pccp/pubs/03047.
A new manual, National Cooperative Highway Research
Program (NCHRP) Research Results Digest No. 281, was released in September
2003. Titled Aggregate Tests for Portland Cement Concrete Pavements: Review
and Recommendations, the manual may be obtained at
http://gulliver.trb.org/publications/nchrp/nchrp_rrd_281.pdf.
Newly released NCHRP Report 499, Effects of
Subsurface Drainage on Performance of Asphalt and Concrete Pavements, by
Kathleen T. Hall and Carlos Correa, and sponsored by the American
Association of State Highway and Transportation Officials and the FHWA, now
is available for download. Access it at
http://trb.org/publications/nchrp/nchrp_rpt_499.pdf
Information about Fort Miller Group’s SUPER-SLAB
precast pavement slab product may be obtained at
www.fortmiller.com/Superslab.htm, including a .pdf brochure.
Public Roads Magazine, an FHWA journal, published a
special issue on concrete pavement technology in July/August 2002. Access
the articles at
www.fhwa.dot.gov/pavement/index.htm.
Reprinted from Better Roads Magazine
April 2004 |
