July/August
2002
Fine-Tuning
Innovative Technologies
by
Mark Swanlund
Field
trials around the country are generating results on alternative designs
for improving high-performance concrete pavements.
To encourage
the use of innovative technologies in concrete pavement, the Federal
Highway Administration (FHWA) is testing and evaluating new concrete
pavement designs and construction concepts through field projects
around the United States. An FHWA program, High Performance Concrete
Pavement (HPCP), has the overall objective of providing long-lasting,
economical portland cement concrete pavements that meet the specific
performance requirements of their particular application.
HPCP
Program Goals - Increase
the service life of portland cement concrete
- Decrease
construction time
- Lower
life-cycle costs
- Lower
maintenance costs
- Construct
ultra-smooth-ride pavements
- Incorporate
recycled or waste products while maintaining quality
- Use
innovative construction equipment or procedures
- Employ
innovative initiatives
|
Since
the program's inception in 1995, more than 23 projects in 13 States
have been constructed or approved. Projects include joint sealing
alternatives, alternative load transfer devices, durable concrete
mix designs, and alternative surface finishing techniques. Although
many projects
are relatively new, several have produced preliminary or final reports.
The results fall into five general categories: joint sealing, fiber-reinforced
concrete, durable concrete mixtures, alternate dowel bars, and surface
texture and noise.
Joint
Sealing
The purpose
of joint sealing is to provide a way of keeping rainwater from entering
the pavement and causing erosion of the base and subsequent faulting
and joint distress.
New joint sealing technologies are intended to provide a longer-lasting
and cost-effective seal. Some in the concrete pavement community believe
that leaving joints unsealed will provide equal pavement performance
at a reduced cost.
|
Several
States are evaluating the most appropriate method for sealing
joints in jointed concrete pavement. |
Projects
in Kansas and Ohio evaluated joint sealing technologies, including
hot poured asphalt, silicone, pre-formed compression seals, unsealed
joints, and alternate joint geometry.
"Results
to date indicate that the pre-formed compression seals are performing
better than the hot poured asphalt or silicone sealants," says
Anastasios M. Ioannides, associate professor of civil engineering
at the University of Cincinnati. "Many joints sealed with the
latter exhibit adhesion failures, although several continue to perform
well. The easier a material is to apply on the site, and the less
demanding it is for elaborate field procedures, the more likely it
is to perform well."
Ioannides
continues, "To answer the question of whether to seal or not
to seal, however, many other pavement performance factors must be
considered, and these do not appear to be related to sealant performance
per se. The test site will be a resource for future observations over
many years."
Fiber-Reinforced
Concrete Pavements
The perceived
benefits of using fiber reinforcement on concrete pavements include
increased fatigue resistance, decreased shrinkage cracking, and increased
joint spacing.
Projects
in Maryland, Missouri, and South Dakota investigated fiber-reinforced
concrete for pavement. The technologies tested include steel fibers,
polyolefin, and polyester fibers at various dosage rates.
The results
to date in South Dakota indicate no significant performance differences
between the 20.3-centimeter and 16.5-centimeter (8-inch and 6.5-inch)
fiber-reinforced concrete pavement and the 20.3-centimeter Jointed
Plane Concrete Pavements (JPCP) control sections. The unjointed fiber-reinforced
concrete pavement experienced transverse cracks at approximately 26-meter
(85-foot) spacing. The initial cost of the 20.3-centimeter fiber-reinforced
concrete pavement was $28.90 per square yard compared with an initial
cost of $15.35/yd2 for the JPCP control section.
In Missouri
the 12.7-centimeter and 15.2-centimeter (5-inch and 6-inch) fiber-reinforced
concrete pavements exhibited significant transverse cracking soon
after construction. The steel fiber pavement experienced transverse
cracking within 0.3 meter (1 foot) of the transverse joint, while
the polyolefin fiber pavement experienced transverse cracking near
mid-panel. According to reports, the12.7-centimeter
thickness test sections were removed and reconstructed due to transverse
cracking and spalling.
According
to Tim Chojnacki, director
of research at the Missouri Department of Transportation, "While
there were some thin test sections, the fibers in the other sections
are doing what they should, keeping cracks closed, and the ride is
excellent."
The 22.9-centimeter
(9-inch) polyolefin and steel fiber-reinforced test sections exhibited
some minor transverse cracking while the 22.8-centimeter and 27.9-centimeter
(9-inch and 11-inch) control section without fibers experienced no
cracking to date. In terms of cost, the steel and polyolefin fiber
added approximately $47 per cubic yard and $60/yd3 to the
cost of furnishing concrete for this project. Based on the experience
in South Dakota and Missouri, it does not appear that fiber-reinforced
concrete pavements are cost-effective, but the long-term benefits,
if any, cannot yet be discounted.
Durable
Concrete Mixes
Aspects
of concrete that can lead to increased durability include larger top-sized
aggregate, low water/cementitious ratio (w/c), fly ash, ground granulated
blast furnace (GGBF) slag, and two-lift construction. Larger aggregates
will reduce the paste fraction of the concrete, thus reducing the
shrinkage potential. The objective of using lower w/c ratio, fly ash,
and GGBF slag is to create a dense concrete with lower permeability.
Two-lift construction allows the use of a lower-cost material on the
bottom of the concrete slab, while a durable, higher-quality concrete
can be used on the wearing surface.
Projects
in Kansas, Ohio, and Virginia used pavements with concrete mixes thought
to be more durable than typically used. The results from the Virginia
project illustrate that air-entrained paving concrete with satisfactory
strength, low permeability, and volume stability can be prepared using
concrete with Class F fly ash or slag, and with 2.5-centimeter and
5-centimeter (1-inch and 2-inch) maximum size aggregates.
"Results
indicate that the specified strength and durability are achieved,"
says Dr. Celik Ozyildirim, principal research scientist at the Virginia
Transportation Research Council, "and the early performance is
satisfactory."
Results
from the Kansas project indicate that the two-lift construction process
using either recycled asphalt pavement or local polishing limestone
in the base and an igneous rock or low w/c ratio concrete in the top
layer can be constructed effectively. The two-lift construction technique
added approximately $25/yd2 to the overall construction
cost. The two-lift construction costs included
a second batch plant, extra hauling of material, a concrete belt
placer/spreader, and extra labor
for hauling.
The Ohio
project led to the conclusion that "The use of GGBF [Ground Granulated
Blast Furnace] slag in concrete pavement produces a higher durability
concrete with lower permeability while maintaining constructability
and reducing cost," according to Shad M. Sargand, professor of
civil engineering at Ohio University and associate director of the
Ohio Research Institute for Transportation and the Environment. "Slag
cement slows down the concrete curing process.To prevent early cracking,
special attention should be given to be environmental conditions during
the first 48 hours of the curing process."
Alternate
Dowel Bars
Alternate
dowel bar systems reduce the distress from corrosion that is characteristic
of epoxy-coated dowel bars. Projects evaluating alternate dowel bars
were constructed in Illinois, Iowa, Kansas, Ohio, and Wisconsin.
Alternate dowel bar technologies evaluated included fiber-reinforced
composite (FRC), grout-filled FRC, stainless steel, stainless steel-clad,
and grout-filled stainless steel tubes.
Results
from all the States indicate satisfactory performance to date from
all alternate dowel bar systems. The FRC dowel bars typically have
lower deflection load transfer efficiency, however, than the conventional
technology epoxy coated steel or stainless steel dowel systems, an
alternative technology. This lower deflection load transfer can be
attributed to lower bending stiffness of the FRC dowels.
"Significant
stresses were generated in the dowel bars and in the concrete surrounding
them after the concrete was placed," says Sargand. "Temperature
gradients in the concrete slabs caused high stresses in the bars,
and stress levels generated in the fiberglass dowel bars were less
than those generated in the epoxy-coated steel bars."
FRC dowels
typically cost between $710 each, while stainless steel-clad
dowels cost approximately $14 each, and solid stainless steel dowels
cost more than $20 each. The typical cost of epoxy-coated steel dowels
is approximately $3 each. This cost difference is significant because
of the number of dowels used in a jointed concrete pavement. A typical
3.6-meter by 4.6-meter (12-foot by 15-foot) jointed
concrete pavement slab will
contain 12 dowels, so an increase of $1 for each dowel will increase
the finished cost by $0.75/yd2.
Surface
Texture and Noise
Adding
texture to concrete pavement provides a safe, durable pavement surface.
Some uniform transverse tined texture, however, can produce an annoying
"whine" under traffic. Projects in Colorado, Iowa, Michigan,
Minnesota, North Dakota, and Wisconsin that evaluated surface texture
and noise investigated alternatives to uniform transverse tined texture
that do not exhibit a whine while still providing adequate surface
friction. The texturing techniques evaluated included uniform transverse
tined, random transverse tined, random skewed tined, longitudinal
tined, and exposed aggregate surface.
"The
difference between the loudest and quietest pavement was about 7 to
8 decibels," says David Kuemmel, P.E., adjunct professor of civil
and environmental engineering at Marquette University in Milwaukee,
WI. "That's a 100 times difference in noise pressure."
The results
indicate that quiet pavement surfaces that also provide adequate surface
texture for wet-weather safety can be constructed on concrete pavements.
"Within concrete pavements," says Kuemmel, "we found
that the more texture you put for safety, the more noise you get.
But if you texture in a longitudinal pattern instead of traverse tine,
you can get as quiet as or almost as quiet as an asphalt pavement
with the same amount of texture."
The recommended
surface texture pattern from the research in Wisconsin is a random
skewed tine spacing with the spacing varying from 10-millimeters to
57 millimeters (0.4-inch to 2.25-inch) over a 3-meter (10-foot) pattern.
The specific pattern recommended is important and can be obtained
at the following Web site: www.trc.marquette.edu/noise&texture/index.html.
WisDOT
has implemented the recommended pattern, with the option of skewing
given to the contractors. "The safety aspects of longitudinally
tined PCC pavements are currently being investigated," says Debra
Bischoff, technology advancement engineer with WisDOT's Bureau of
Highway Construction. "The results of that study will dictate
whether or not WisDOT approves the use of longitudinal tining on Wisconsin
highways."
In summary,
the FHWA program to test and evaluate innovations in concrete pavement
technology through field trials demonstrated that we can produce longer-lasting
high-performance concrete pavements. In terms of cost, the results
are mixed. Surface texture technologies and durable concrete mixes
hold the promise of being cost-effective, while fiber-reinforced concrete
pavements have not been shown to be cost-effective to date. Based
on the work done in this project, no definite conclusion was reached
on joint sealing, and the jury is still out on alternate dowel bars
as well.
Summary
of High Performance Concrete Pavement Projects
Project
| Pavement
Type | Design
Features Evaluated | Year
Built |
---|
Illinois
1
I-55 SB, Williamsville | JRCP |
Alternative Dowel Bar Materials | 1996
|
---|
Illinois
2 IL
59, Naperville | JRCP
JPCP | Alternative
Dowel Bar Materials Sealed/Unsealed
Joints Traffic
Counters | 1997 |
---|
Illinois
3
U.S. 67 WB, Jacksonville | JPCP | Alternative
Dowel Bar Materials Sealed/Unsealed
Joints | 1999 |
---|
Illinois
4 SR
2 NB, Dixon | JPCP |
Alternative Dowel Bar Materials | 2000 |
---|
Iowa
1a
IA 5, Carlisle | JPCP |
PCC Mixing Times on PCC Properties | 1996 |
---|
Iowa
1b U.S.
30, Carroll | JPCP |
PCC Mixing Times on PCC Properties | 1996 |
---|
Iowa
2
U.S. 65 Bypass, Des Moines | JPCP | Alternative
Dowel Bar Materials Alternative
Dowel Bar Spacings | 1997 |
---|
Kansas
1
K-96, Haven | JPCP
FRCP | Alternative
Dowel Bar Materials Alternative
PCC Mix Designs (incl.
Fiber PCC) Joint
Sawing Alternatives Joint
Sealing Alternatives Surface
Texturing Two-Lift
Construction | 1997 |
---|
Maryland
1 U.S.
50, Salisbury Bypass | JPCP
FRCP |
PCC Mix Design Fiber PCC | 2001 |
---|
Michigan
1 I-75
NB, Detroit | JRCP
JPCP | Two-Lift
Construction
Exposed Aggregate
Thick Foundation | 1993 |
---|
Minnesota
1
I -35W,
Richfield | JPCP | Alternative
Dowel Bars
PCC Mix Design | 2000 |
---|
Minnesota
2 Mn/Road
Low Volume Road Facility, Albertville | JPCP | Alternative
Dowel Bar Materials Doweled/Nondoweled
Joints PCC
Mix Design | 2000 |
---|
Mississippi
1
U.S. 72, Corinth | Resin-
Modified Pavement |
Alternative PCC Paving Material (Resin-Modified
Pavement) | 2001 |
---|
Missouri
1
I-29 SB, Rock Port | JPCP
FRCP | Fiber
PCC
Slab Thickness
Joint Spacing | 1998 |
---|
New
Hampshire 1 | N/A | HPCP
Definitions
"Design Optimization" Computer Program | N/A
|
---|
Ohio
1
U.S. 50, Athens | JRCP |
PCC Mix Design | 19971998
|
---|
Ohio
2
U.S. 50, Athens | JRCP | Alternative
Dowel Bar Materials | 1997 |
---|
Ohio
3 U.S.
50, Athens | JRCP | Sealed/Unsealed
Joints PCC
Mix Design | 19971998
|
---|
South
Dakota 1
U.S. 83, Pierre | JPCP |
Joint Spacing FRCP
Doweled/Nondoweled Joints | 1996 |
---|
Virginia
1 I-64,
Newport News | JPCP | PCC
Mix Design | 19981999
|
---|
Virginia
2
VA 288, Richmond | CRCP | PCC
Mix Design Steel
Contents | 2000 |
---|
Virginia
3 U.S.
29, Madison Heights | CRCP | PCC
Mix Design Steel
Contents | 2000 |
---|
Wisconsin
1
WI 29, Abbotsford | JPCP |
Surface Texturing | 1997 |
---|
Wisconsin
2
WI 29, Owen | JPCP |
Alternative Dowel Bar Materials Alternative
Dowel Bar Spacings | 1997 |
---|
Wisconsin
3 WI
29, Hatley | JPCP |
Alternative Dowel Bar Materials Alternative
Dowel Bar Spacings
Trapezoidal Cross Section | 1997 |
---|
Legend
JRCP:
Jointed Reinforced Concrete Pavement
JPCP:
Jointed Plain Concrete Pavement
FRCP:
Fiber-Reinforced Concrete pavement
CRCP:
Continuously Reinforced Concrete Pavement
References
1. Lea,
F. M., The Chemistry of Cement and Concrete, 3rd edition, Chemical
Publishing Company, Inc.
2. Wong, G.S, et al., Portland Cement Concrete Rheology and Workability
- Final Report, FHWA Report No. FHWA-RD-00-025, Federal Highway
Administration, Washington, DC, April 2001.
3. Popovics, S., Fundamentals of Portland Cement Concrete: A Quantitative
Approach, John Wiley, 1982.
4. Japan Concrete Institute Technical Committee on Autogenous Shrinkage
of Concrete, Committee Report, Autogenous Shrinkage of Concrete, Ei-ichi
Tazawa, Ed. London and New York: E & FN Spon, 1999.
5. Magura, D.D., Air Void Analyzer Evaluation, FHWA Report
No. FHWA-SA-96-062, Federal Highway Administration, Washington, DC,
1996