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Research Report Abstracts

ET-2000 Extruder

ET-2000 Extruder Guardrail End-Terminal
 
An ET-2000 Extruder Guardrail End Terminal (GET) was installed in September 1993 along a state highway in southern Oregon. The ET-2000 GET was installed to reduce the severity of injuries during accidents and to reduce the amount of land (right-of-way) required for the guardrail.  The ET-2000 GET was installed as planned- there were no major problems during construction.  The performance of the ET-2000 GET should be evaluated by ODOT staff for at least two years.  Based on the successful experiences of other states, ET-2000 GET should be allowed to be used as an alternative guardrail end terminal.  Any additional ET-2000 GET'S installed by ODOT should be monitored.


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Automation Project

Woodburn Port-of-Entry Automation Project
 
In 1986, the Oregon State Highway Division (OSHD), in conjunction with the Public Utility Commission (PUC), and with the cooperation of the Federal Highway Administration (FHWA), undertook an experimental project at the Woodburn southbound Port-of-Entry (POEI.  The plan was to automate this POE to minimize the weigh-master and PUC tasks; improve weight, size, and safety enforcement; provide more data for planning and design purposes; and save human resources and time for the State and the trucking industry.  The weigh-in-motion (WIM) scale, automatic vehicle identification (AVI) system, and static scales, along with the PUC motor carrier database would be tied into a supervisory computer system which would control truck traffic and data.
 
This report presents findings from five years of operations and describes the construction and automation of the Woodburn POE, including the physical plant, the hardware and software, system operation, data obtained, benefits, limitations, conclusions and recommendations.
 
This project is a success, even though all the theoretical benefits were not achieved, because only a few trucks carried transponders.  Enough actual benefits exist to consider this experiment a success.  These benefits include improved weight and safety enforcement, data collection access, human resources savings, weigh-master productivity gains, vehicle screening, capital expenditure savings, and increased trade productivity. The monetary benefits greatly exceed the automation costs.
 


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Two-Rail Steel Final

Two-Rail Steel-Backed Timber Guardrail System

In 1920, to provide for the safety of drivers on the Columbia River Highway, two-rail timber guardrails were installed. Subsequently, the two-rail timber guardrails were replaced by more modern guardrail.  Recently, the Historic Columbia River Highway Advisory Committee requested that the Oregon Department of Transportation (ODOT) install the old style two-rail guardrail on the Historic Columbia River Highway (HCRH).  To satisfy the current crash testing standards, ODOT staff modified the guardrail by reinforcing the rails with galvanized steel.  The two-rail steel-backed timber guardrail was successfully crash tested and installed on the HCRH.
 
In March 1992, the guardrail was installed using Douglas-fir for the posts and rails and galvanized steel as backing for the rails.  The guardrail was installed with few delays, although it was more time consuming than standard guardrail installation.  The cost to install the two-rail steel-backed timber guardrail was $134.50/meter ($41.00/foot), which is about 3 ½ times more costly than the typical Type 2A guardrail.  The wood was pressure treated with ammoniacal copper zinc arsenate (ACZA), which leached out, discoloring the paint and corroding the galvanized steel.
 
ODOT Research Unit staff evaluated the two-rail steel-backed timber guardrail for two years as part of an Experimental Features research project.  Recommendations from this research include:

  1. sting guardrail,
  2. continue the evaluation of the guardrail by maintenance staff,
  3. identify a funding source for routine maintenance,
  4. revise the ODOT specifications for drying guardrail posts and rails, and
  5. for future projects, the sealant and paint should be specified in the Special Provisions.
 


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Geotextile Fabrics Interim Report

Geotextile Fabrics Under an Asphalt Concrete Overlay to Retard Reflective Cracking
 
The City of Portland identified pavement surface distress on East Burnside Street between East 39th Avenue and East 47th Avenue. Therefore, the City developed a construction project to improve the pavement. The project included cold planing, an asphalt concrete leveling course, geotextile fabrics, and an asphalt concrete overlay.
 
The City of Portland decided to use geotextile fabrics for pavement reinforcement and crack retardation. In September 1991, the City placed Glasgrid and Polyguard geotextile fabrics on East Burnside Street. If the fabrics successfully retard reflective cracking, the City anticipates the following benefits:
 

  1. Reduction of water infiltration into underlying cracks;
  2. Retardation of vegetation growth in cracks;
  3. Improvement of pavement surface quality; and
  4. Reduction of future pavement maintenance costs.
 
Over two years have elapsed since the installation of the geotextile fabrics. The overlay over the geotextile fabrics has been inspected twice since construction. The inspections revealed some cracks in the section without the geotextile fabrics. However, the cracks are small and the performance of the test and control sections are similar; additional time is needed to evaluate the sections to determine if the City of Portland will receive the benefits listed above.
 
Inspections will be conducted annually until at least 1996 or until the test and control sections fail. Then, if enough information exists to determine the cost effectiveness of the geotextile fabrics (Glasgrid and Polyguard) a final report will be written.


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Asphalt Paving Mixtures

Field Control of Asphalt Paving Mixtures
 
The Oregon Department of Transportation (ODOT) controls the quality of its AC paving mixtures by using a statistical pay factor system based on random sampling and testing of aggregate gradation, asphalt content, and compaction density.  Concerns about potential toxicity of solvents used for asphalt extraction led to the desire for less hazardous quality control procedures.  As a result, ODOT eliminated the use of solvents.  Asphalt content is now controlled using a nuclear gage and aggregate gradations are determined from cold feed samples. The goal of this study was to develop information and evaluation new methods for controlling quality of the AC mixture in the mat.  Specifically, this research project evaluated using a gyrator compactor in the field laboratory to determine mix quality.  Specimens were prepared from companion mixture samples using both gyratory and kneading compaction.  The properties of  the mixtures were compared using a Varity of standard tests including density, voids, Marshall stability, Hveem stability, etc. The results of this research study include the following conclusions and recommendations:
conclusions:
1.  The gyratory compactor worked well in the field laboratory.  Compared to the kneading compactor, it is relatively inexpensive and simply to operate.  The compacted specimens appear to represent the mixture quite well as shown by density and voids.
2.  The measured stability values on gyratory compacted specimens are equal to or better than  those for kneading compacted specimens; the results appear to be more consistent than with kneading or Marshall compacted specimens.
3.  AC mixtures can be controlled in the field by monitoring stability; however, there is significant 
variability in the results.
4.  The void content measured in gyratory compacted field specimens may be used as a field control parameter. Recommendations:
1.   The gyratory method of compaction should be advanced as a method of field acceptance for
      asphalt concrete mixtures.  This should be delayed until the new SHRP compactor is available.
2.   Track the field performance of the four projects evaluated in this study for a period of 2-3       years to see if actual performance correlates with any of the test results evaluated.
3.   Develop  specifications for controlling asphalt concrete mixtures with a field compaction device       used to fabricate specimens to measure air voids and voids in the mineral aggregate (VMA). 
 

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Porous Pavements

Evaluation of Porous Pavements for Road Surfaces
 
Porous pavements or open graded asphalt mixtures have been in use in Oregon since the late 1960s. The use of this pavement type has increased over the years because the pores in the mat provide a better way for water to drain from the surface. This greatly increases the safety in the areas of skid resistance and splash and spray. Added benefits to these pavements are that sound emitted from tire noise is partly absorbed into the voids of the pavement.
 
Not all the attributes of porous pavements are beneficial. There have been some durability and construction problems associated with this pavement type. Experience and trial and error have reduced many of the disadvantages of porous pavements. Recent experiences with these mix types in the U.S. and abroad have been positive.
 

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Recycled Plastics

Recycled Plastics in Highway Construction and Maintenance
 
Oregon Senate Bill 66 directed the Oregon Department of Transportation to conduct a research project to evaluate the use of recycled plastic products and composite materials containing recycled plastic in construction and maintenance.  This report documents the installation throughout the state of snow poles, sign supports, fence posts, and a sound wall.
 
Recycled plastic materials may be more difficult to obtain than standard wood products.  Upfront material and shipping costs are more expensive than comparable wood products.  Handling of recycled plastic materials is similar to handling treated wood products except recycled plastic materials are heavier.  Recycled materials may be more readily recyclable than treated wood products.
 
Recycled snow poles were easier to install than standard snow poles.  Recycled plastic sign supports, fence posts, and sound wall materials, in general, were more difficult to install.
 
Recommendations from this study include the following:
1.  Additional recycled plastic material installations should be encouraged to obtain more information regarding the constructability of recycled plastic materials;
2.  Recycled plastic fence post for installations in areas with dense soils should be ordered with a point at one end;
3.  Recycled fence post should be installed by pushing with steady pressure rather than driven with repeated blows; and
4.  Recycled plastic boards used for sound wall facing should have tongue and groove joints to insure proper interlocking and to reduce the amount of blowing.


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Polymer Modified Asphalt Test

Field Test of Polymer Modified Asphalt Concrete (Murphy Rd. to Lava Butte Section)
 
Polymer additives to asphalt materials are claimed to have a high potential for improving long-term pavement performance through their ability to enhance the properties of the asphalt binder and of the resulting concrete mix. In 1989, the Oregon Department of Transportation (ODOT) initiated a research study to evaluate the field performance of three polymer modified Asphalts. The polymer-modified Asphalts evaluated included: 1) StyrelfR - a polymerized binder with a thermoplastic styrene-butadiene block copolymer (SB), 2) AC-20R - a polymerized binder with a thermosetting styrene-butadiene latex anionic polymer (SB), and 3) CA)P)-1 - a polymerized binder with a thermoplastic ethylene-vinyl-acetate random copolymer.  The three polymer modified asphalt concertos were constructed in five separate test sections adjacent to each other.  In addition to the use of polymer modified asphalt, two control sections with a conventional AC-20 asphalt were constructed for comparison of performance.
This final report presents a comprehensive evaluation of the materials used on this project and their performance up to June 1993.  Field survey results indicate that the primary surface distress on all sections is transverse cracking with varying spacing.  this transverse cracking very likely resulted from reflective cracking from the base course and the existing pavement.  The level of severity ranged from low to medium.  The AC-20 (control) sections showed a more noticeable loss of aggregated than polymer modified AC sections.  In general, both the AC-20 (control) sections and polymer modified (test) sections have been performing well.  There is no clear distinction as to which section is superior.  All sections of pavement have carried over 1.5 million equivalent axle loadings since the construction.


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ARMORFORM

ARMORFORM Articulating Block Mat Erosion Control System
 
The ARMORFORM Articulating Block Mat (ABM) was constructed at the Salmon Creek Bridge abutments during the summer of 1991.  The bridge is located on the eastside of Oakridge, Oregon.  A construction report, prepared in October 1991, details the ABM construction.  This report presents the ABM performance to date based on site visits performed in August 1992, August 1993, and September 1993; and discussions with field personnel.
 
Based on the field inspections, the ABM appears to be performing as intended.  Because the nature of the ABM did not allow it to be wrapped around the bridge abutments, the corners of the mat were not keyed in.  Of interest, is the northwest (upstream) bridge abutment area which had been undermined prior to construction.  The northwest corner of the mat is currently exposed and could provide an avenue for failure during a major flood event.  Riprap has been added but should be monitored to insure the corner is adequately protected, so that the stream flow is not allowed behind the mat.
 
The ABM will be inspected annually and during or immediately after any 25-year flood events.  This study is expected to continue until 1996.


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Rigid Pavement

Rigid Pavement Performance Data

Pavement structure, condition ratings, and distress were used to characterize the performance of rigid pavements in Oregon.  Data from jointed and continuously reinforced concrete pavements ranging in age from 2 to 32 years were collected. Sixty-two experimental sections were identified along Interstate routes representing the range of environmental conditions in Oregon.
 
All Oregon rigid pavements are performing very well structurally.  Older pavements have carried 2 to 6 times their design traffic, yet maintain serviceability indices above 3.0.  Distress types commonly associated with the need for rehabilitation were not generally evident.  Efforts to predict pavement distress development with structural, environmental, and loading data were unsuccessful.
 


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Swift Delta I-5 Interchange

A Numerical Invest. into the Performance of the Soil Nail Wall and Pile Foundation at Swift Delta I-5 Interchange
 
Finite Difference Methods (FDM) and Finite Element Methods (FEM) studies are reported studying the soil nail wall construction at the Swift Delta 1-5 Interchange bridge reconstruction in North Portland, Oregon.  Five (5) layers of soil nails were installed between existing bridge supporting pipe piles, and a shortcrete finished face applied to stabilize the fill sand.  Instrumentation on the project at two sections, S1 and S2, included strain gages on the nails, and on a single pile at S1, load cells on the nail heads, inclometers in the wall and in the fill at S2 outside of the bridge, and tiltmeters with an extensometer on the pile cap at S1.
 
Some interpretive comments are made on the measured wall and nail readings, which are used to back calculate possible earth pressures by FDM techniques.  The lateral load program COM624P is used to explore the limitations of FDM techniques for direct pile analysis in Swift Delta's soil nail pile system.  Two dimensional FEM analyses are conducted by a new code, Finite Element analysis of NAILS (FENAIL), written specifically for this study.  Modeling in both linear elasticity, and nonlinear plasticity, is reported at the bridge instrumented section S1 and the wall section S2 outside the bridge footprint.  The model features included: full geostatic conditions, excavation modeling sequences and nail activation with beam elements. An innovative interference element is introduced to link the "out of mesh" pile to the soil and nail model, and generate pseudo 3 dimensional (3D) effects.
 
A full 3D FEM analysis is reported of the top soil nail, adjacent pile and soil, by the code ABAQUS running on a CRAY MPX supercomputer.  Linear elastic, anisotropic elastic and a single elastic plastic model were completed to study interaction and global stiffness contributions from the pile and nail.
 
Based on FENAIL work overall replication of the Swift Delta soil nail wall is good.  In general, only limited pile influence can be seen and deflections and stresses do not appear highly sensitive to the piles presence.  The reinforced soil mass behaves similar to a reinforce wall structure without piles.  The lack of any significant pile influence is also found in the 3D ABAQUS study under nail tension conditions.  However, the pile's lateral load stiffness response is improved by nailing of the soil mass.
 
 


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Open-Graded "F" Mix

Evaluation of Open-Graded "F" Mixtures for Water Sensitivity
 
The Oregon Department of Transportation (ODOT) has increased their use of open-graded paving mixtures.  During the last five years, ODOT has constructed several hundred miles of highways with open-graded "F" asphalt concrete mixtures. These pavements have performed well, with no known failures attributable to moisture damage.
 
In 1992, many "F" mixtures failed the Index of Retained Strength (IRS) test used by ODOT to evaluate the water damage potential of asphalt concrete mixtures.  Although "F" mixtures had difficulty passing the IRS test, ODOT engineers felt that the problem was not with the "F" mixtures, but with the test itself.
 
This study investigated the suitability of implementing the Strategic Highway Research Program's (SHRP) Environmental Conditioning System (ECS) procedure for evaluating the water sensitivity of "F" mixtures.  As a part of this study, test data was collected using the IRS test and the ECS test for several different "F" mixtures.  The IRS procedure is more severe that the ECS, indicating potential pavement failure problems where they don't exist and that are not predicted by the ECS. The IRS test may not be suitable for "F" mixtures. The ECS procedure shows promise as a test method for evaluating water sensitivity of "F" mixtures, but further evaluation and correlation with field performance is required.


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Latex-Modified Fiber-Reinforced Concrete

Latex-Modified Fiber-Reinforced Concrete Bridge Deck Overlay
 
In an attempt to increase the tensile strength of LMC and reduce cracking, steel fibers were added to a LMC mix. The results are what is termed as "latex- modified, fiber-reinforced concrete" (LMFRC). LMFRC was placed on Hayden Bridge as an experimental overlay.
 
The LMFRC overlay has performed well and has not yet developed any visible cracks. The overlay has not delaminated or rutted. The skid resistance is comparable to a standard PCC deck.
 
Recommendations for improved construction practices can be found in the Construction1 Interim Report that was prepared in June 1993.  Finally, because of its improved Performance, a LMFRC overlay may be considered as a permitted alternative to LMC.


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Cost-Effect of Thin Pavement

Evaluation of Performance and Cost-Effectiveness of Thin Pavement Surface Treatments
 
This study describes the findings from the study of 87 closely monitored sites in the State of Oregon which were treated with different types of thin surface materials.  All of these surface treatments had a total thickness of two inches or less, and included: chip seals, asphalt penetration macadam or "oil mats", cold in-place recycling (CIR), and thin asphalt concrete overlays.
 
Attempts were made to define the cost-effectiveness using unit cost, traffic loading, and life of treatment, but specific recommendations concerning the relative cost-effectiveness of the treatments studied were not possible with the data from this study.
 
Polymer modified chip seals appeared to be generally more cost-effective than conventional chip seals when traffic loading and cost are factored into the evaluation of treatment life.
 
Chip seals, as used in Oregon, do not correct rutting.  Rather, the opposite is true, there is a tendency for ruts to be slightly deeper after applying a chip seal.
 
This dense-graded, AC overlays appeared to be more cost-effective on a life-cycle basis (LCI), particularly in heavy traffic areas.
 
Construction practices and weather conditions at laydown can significantly affect the life of a thin surface treatment.  The life of any of the treatments studied may be made to last more (or less) time than shown in this study.

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Geotextile Reinforced Bridge

Geotextile Reinforced Bridge Approach Embankment
 
In an attempt to reduce the discontinuity between the bridge and the roadway due to the settlement and/or consolidation of the approach embankment, an experimental construction method was tested on the Lost River Bridge in Klamath County.  The method consisted of combining soil in six 1' lifts, interlaced with the geotextile reinforcement.  This method was designed to reduce the settlement of the newly placed fill, thus reducing the discontinuity.
 
The Lost River Bridge was widened by 10'3" on each side.  The additional width of the bridge required short narrow sliver fills at all four corners.  The geotextile reinforcement was only used in the sliver fills and did not run the whole width of the road-to-bridge transition.  The material was easy to work with considering the small size of the project.  Although the original plans called for the geotextile reinforcement to be used at two of the four corners, to allow for a control lane in the northbound direction, it was used at all four corners.
 
A settlement plate was installed at all fill location before the first lift was put down to measure the settlement of the original soil under the new fill.  The settlement of the new fill will be found by subtracting the original settlement soil from the total fill settlement.
 
The construction of the sliver fills went well.  The soil used for the fills was native soil from the job site.  It consisted of about four different types of soil, and was granular in nature.  Compaction requirements were met by placing each lift with 6 inches of loose soil.
 
The construction of the new sliver fills gave a good ride immediately after construction.  There were no bumps at the road-to-bridge transition.
 

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METRO RUMAC

Rubber Modified Asphalt Concrete (METRO RUMAC) Evaluation
 
This report covers the construction in 1991 of two test pavements using asphalt concrete modified with crumb rubber from scrap tires.  The pavements are on arterial roadways in the Portland, Oregon metropolitan area.
 
Both test pavements use a dense-graded rubber modified asphalt concrete (METRO RUMAC) development for the Metropolitan Services District (METRO) of the Portland metropolitan area.  In this process, crumb rubber made from recycled tires is mixed with aggregate before the asphalt is blended into the mix.  Adjacent to the test pavements, control pavements were paved with conventional asphalt concrete.  The test pavements are compared to these control pavements.
 
The METRO RUMAC was successfully blended in both a batch and a drum mixing plant.  In both cases, the plant’s exhaust gas opacity was an acceptable level.  The rubberized mixes were placed and compacted by conventional equipment.
 
Experience on these projects showed that caution is needed in determining the mix properties by solvent extraction and in measuring pavement density by a nuclear gauge.  Testing showed that two solvents commonly used in vacuum extractions dissolve finer particles of the crumb rubber.  Using mathematical modeling, it was found that solvent dissolving rubber during the extraction had these effects on test results:  it did not significantly affect the test results for the overall gradation of the mix, it had a significant effect on the asphalt content test results, and it invalidated rubber gradation and rubber content test results.  To get accurate nuclear density test results, special care was needed when the gauge was seated on the surface of the METRO RUMAC.
 
After construction, both the METRO RUMAC test sections had appearance, ride values, deflection reductions, and surface friction values similar to there respective control pavements and typical ODOT dense-graded overlays.
 
The METRO RUMAC mixes cost about 1 ½ times more than their conventional counterparts.  Most of this increase was due to the cost of the rubber and the expense of adding the rubber.  At this time, it is not certain that the greater initial cost of these rubberized mixes will be offset by a commensurate increase in the pavement’s service life.


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Two-Rail Steel-Backed Construction Report

Two-Rail Steel-Backed Timber Guardrail System
 
The two-rail steel-backed timber guardrail is an alternate to the standard steel guardrail.  It has been approved by the Federal Highway Administration (FHWA) for use on federally funded projects.
 
A section of Crown Point Highway (Highway 125) was chosen as an Experimental Features Project to evaluate the two-rail steel-backed timber guardrail.  The guardrail was installed in March, 1992 using pressure treated Douglas-fir and galvanized steel as building materials.  The guardrail was installed with few delays, although it is more time consuming than standard guardrail installation.  The cost to install the two-rail steel-backed timber guardrail was $41.00/linear foot, which is about 2 ½ times more expensive than a Type 2A guardrail.  The wood was pressure treated with ammoniacal copper zinc arsenate (ACZA), which leached out, discoloring the pain and corroding the galvanized steel.
 
To achieve a more aesthetic look, the wood should have been left unpainted.  This would let the natural color of the wood show.  More care should be given in drying the wood after it is removed from the preservation vessel to ensure that the ACZA does not leach out.  Smaller posts should be considered in the design to allow for standard construction methods to drive them into the ground, cutting down on construction costs.


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Geotextile Fabrics Construction Report

Geotextile Fabrics Under an Asphalt Concrete Overlay to Retard Reflective Cracking
 
In an attempt to reduce the discontinuity between the bridge and the roadway due to the settlement and/or consolidation of the approach embankment, an experimental construction method was tested on the Lost River Bridge in Klamath County. The method consisted of combining soil in six 1' lifts, interlaced with the geotextile reinforcement. This method was designed to reduce the settlement of the newly placed fill, thus reducing the discontinuity.
 
The Lost River Bridge was widened by 10'3" on each side. The additional width of the bridge required short narrow sliver fills at all four corners. The geotextile reinforcement was only used in the sliver fills and did not run the whole width of the road-to-bridge transition. The material was easy to work with considering the small size of the project.  Although the original plans called for the geotextile reinforcement to be used at two of the four corners, to allow for a control lane in the northbound direction, it was used at all four corners.
 
A settlement plate was installed at each fill location before the first lift was put down to measure the settlement of the original soil under the new fill. The settlement of the new fill will be found by subtracting the original settlement soil from the total fill settlement.
 
The construction of the sliver fills went well. The soil used for the fills was native soil from the job site. It consisted of about four different types of soil, and was granular in nature.  Compaction requirements were met by placing each lift with 6 inches of loose soil.
 
The construction of the new sliver fills gave a good ride immediately after construction.  There were no bumps at the road-to-bridge transition.


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