Research Report Abstracts
Establishing Layer Coefficients for CTB, PMBB, and RAP
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In 1988, the Oregon State Highway Division adopted the 1986 AASHTO guide for pavement thickness design. Currently the OSHD uses a layer coefficient of .22 to .24 for cement treated base (CTB), and .32 for plant mix bituminous base (PMBB). Recycled asphalt pavement grindings (RAP) have been given the same layer coefficient as that used for aggregate base. This study was conducted to determine more specific values which take into account local materials and specifications. Through the use of laboratory triaxial, diametral, and unconfined compressive strength testing equipment, the strength properties of the CTB, PMBB, and RAP were characterized and correlated to AASHTO layer coefficients. The results of the testing for CTB were modified to take into account the new OSHD specification and the unrecoverable cores. The modified data resulted in project average layer coefficients for CTB ranging from .21 to .30. The PMBB project averages for layer coefficients range from .3 to .47. The range in these values is considerable. The current design practice of using layer coefficients of .22 to .24 for CTB and .32 for PMBB will be continued until additional data and specification changes are made to justify a change. The use of RAP in lieu of untreated aggregate base appears to be a good alternate on some projects.
Study of Lime vs. No Lime in Cold In-Place Recycled Asphalt Concrete Pavements
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The resilient characteristics of cold in-place recycled asphalt concrete with and without lime were examined. Six core samples were obtained from a site two months after construction; six months later, six additional core samples were obtained from the site. The samples were tested in the laboratory for resilient modulus.
Conclusions of this study include:
- The resilient modulus of the recycled mix with lime increased substantially in the early stage, as compared to the recycled mix without lime.
- The resilient modulus value of the recycled mix with lime after freeze-thaw conditioning was much higher than the recycled mix without lime.
- Eight months after construction, the resilient modulus of the unconditioned recycled mix with lime was similar to that of the unconditioned recycled mix without lime.
Recommendations of this study include:
- Further evaluate the potential benefit of adding lime to the recycled mix and investigate the effects of adding different percentages of lime to the recycled mix.
- Evaluate the effects of adding quick lime compared to hydrated lime to the recycled mix.
- Appropriate mix design criteria, construction procedures, and field control guidelines should be developed if adding lime to the recycled mix.
Soil Nailing of Bridge Fill Embankment
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Soil nailing as an alternative lateral earth support method has recently been introduced in Oregon to build the first permanent Soil -Nailed Wall on the State's Highway System.
The soil nailing technique was used for an underpass widening to provide for additional traveling lanes under the existing Oregon Slough Bridge in Portland,
Oregon. The project required removal of the existing south end slope and the construction of a Soil-Nailed Wall in front of the pile-supported end bent to permanently retain the existing bridge fill embankment.
Construction and post-construction monitoring was performed t o study the new wall's performance.
This is the first of a five-paper sequence describing the results of ODOT's extensive investigation into the soil nailing technique as an alternative to more conventional bridge embankment retention methods.
Based on the results of our study, it may be concluded that:
- The soil nailing technique is a viable lateral earth support system to retain an existing bridge fill embankment and to allow for a roadway widening under a bridge.
- The selection of the soil nailing support system was based on economic considerations.
This technique enabled
- considerable cost savings to the owner,
- the project to proceed without disrupting overhead bridge or adjacent roadway traffic,
- the Contractor to work in low overhead clearance conditions, and
- the Contractor to quickly alter his construction procedure to fit soil conditions.
Evaluation of Flyash in Lean Concrete Base and Continously Reinforced Concrete Pavements
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This report documents the five-year performance of a continuously reinforced concrete pavement constructed with fly ash. The study area was located on Interstate 5 (Southbound), south of Albany, Oregon. Visual inspections of the pavement surface, final laboratory test results and recommendations for use are included in this report.
Piezo-Electric Automatic Vehicle Classification System
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Oregon has twelve pavement test sites that are part of the Strategic Highway Research Program (SHRP), Long Term Pavement Performance (LTPP) studies. Part of the data gathering on these sites involves vehicle weight and classification. This pilot project was to help SHRP show others how to specify, procure and install equipment that would provide the necessary data to characterize the sites for the LTPP program.
Castle Rock Consultants (CRC) provided specifications and technical aid for the first phase of this project. After the first phase was completed, CRC produced a paper for SHRP titled, "Piezo-Electric Based Automatic Vehicle Classifier Pilot Project," December, 1989. This report complements the CRC report and discusses the total project from Oregon's perspective.
This report covers procurement of equipment and installation on two pilot sites, one for asphalt concrete (AIC) and the second for Portland cement concrete (PCC). Oregon used the results from this study to write the specifications for contractor installation of the ten remaining sites.
AC/CRC Adjacent Lane Surfacing
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Asphaltic Concrete (AC) and Portland Cement Concrete (PCC) are common roadway materials used in Oregon. In a recent construction project -- Poverty Flats/Meacham Section -- the Oregon State Highway Division (OSHD) designed, as part of the project, a "test section" consisting of one AC lane and one Continuously Reinforced Concrete (CRC) land parallel to each other. With a lightly-used inside lane of AC, and a heavily-traveled outside lane of CRC, it was believed that the pavement would have the superior strength, durability, and life span of CRC, yet a lower price than all-CRC pavement. The goals of the study are to determine the performance, safety, and cost-effectiveness of this "AC/CRC Adjacent Lane Surfacing."
A 5-mile AC/CRC test section was built as part of a 12-mile-long upgrade from all-AC to all-CRC surfacing on Interstate 84 between milepoints 225 and 238, in Northeastern Oregon. The climate generally has mild summers and cold, harsh winters. Heavy trucks make up a large percentage (39%) of the daily traffic, and about 90% of those trucks drive in the outside lane. This combination of severe traffic and environment is very hard on AC surfacing and is the reason for this upgrade.
The majority of the existing AC pavement was removed and placed into the median and drainage ditches as granular fill. The remaining pavement was left in place and used as a base for the new CRC pavement (and for the new AC inside lane within the test section). Outside the test section, the CRC was placed in both lanes. Within the test section, the outside lane was built with CRC as described above, while the inside lane was "milled down" and paved with AC. The shoulders were then paved with AC.
Oregon Asphalt-Concrete B-Mix Improvement Study
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The Oregon State Highway Division (OSHD) has experienced rutting and/or raveling pavements in Oregon Class "B" asphalt concrete in the last two decades. Some of these pavement problems have evolved from material changes or changes in construction practices.
The typical agency reaction to these problems has been to make adjustments in paving mixture components and mixture characteristics. These changes to mixtures have sometimes created unexpected pavement problems.
Test mixtures composed of five different aggregate gradations and up to seven asphalt cement types were fabricated in the laboratory. Several index and performance tests were performed on each mixture. These test results were compared to current OSHD paving mixture design criteria.
This study concluded that a gradation slightly coarser than the maximum density gradation in the 1-1/4 inch fraction and significantly coarser than the maximum density in the 1/4-0 inch fraction should improve mixture performance. This study also concluded that conventional asphalt is satisfactory unless environment or construction conditions dictate a need for a modified asphalt.
Oregon has implemented the recommended gradations from this study. Oregon has also discontinued the use of component based modified asphalt specifications for most paving projects. Only projects with harsh environmental conditions employ modified paving asphalt, and they are under a performance based specification.
Condition Monitoring of Continuously Reinforced Concrete Pavement
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This four-year study includes annual monitoring data from twenty-seven pavement sites in Oregon that were constructed using Continually Reinforced Concrete Pavements (CRCP). Most of these pavements were between fifteen and twenty-five years old when the last distress survey was performed in 1988. Some of them have endured nearly fifteen million ESAL’s and continue to perform well.
A comparison is made of distress observed in the field to distress predicted by equations developed for Texas and Illinois pavements. Oregon’s CRCP show significantly less distress than those equations predict. Thus Oregon’s CRCP have a longer service life (time to full depth overlay), than the twenty years anticipated. To develop failure prediction equations for Oregon, additional research is needed.
Experimental Project Use of Shredded Tires for Lightweight Fill
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Shredded rubber tires have been used as Lightweight fill in repair of a landslide that occurred under a highway embankment in mountainous terrain on Highway US 42 (Oregon state route #35). The force driving the slide was decreased by removing the soil embankment and replacing it with a lighter weight embankment constructed with shredded tire chips. The tire embankment has a three-foot-thick compacted soil cap on the top and side-slopes and supports a conventional aggregate base and asphalt pavement. 5800 tons of shredded tires were used - approximately 580,000 tires. Cost of the tires delivered to the site was $30/ton reduced by a $20/ton reimbursement from Oregon DEQ; net $l0/ton ($7/yd). Cost of placing and compacting the tires was $8.33/ton: ($5.85/yd). Total cost of the tire fill at final in-place density was $18.33/ton ($12.87/yd). Surface monuments, settlement plates, and slope inclinometers have been installed to monitor the performance of the embankment.
Shredded tire chips were transported to the project site in “live-bottom" trailers from vendors located 150 to 200 miles from the project. The trailers each carried 28 tons of tires. The tire chips were placed and compacted in three-foot lifts using a D-8 dozer. Density (unit weight) of the tire chips was on the order of 30 per when "loose" in the haul vehicle, 45 pcf compacted in-place, and 52 pcf when compressed under the soil cap and pavement. The 12.5-foot-thick section of compacted tire embankment compressed 20 inches (13.4%) under the capping load. Few construction problems were encountered. Exposed wires in the tire chips caused tire punctures on dump trucks.
Pavement surface deflections were measured using a falling weight deflectometer. Deflections were twice as great as would be expected of the same pavement over an earth embankment. Vibrations similar to those felt when standing on a bridge can be felt by a person standing on the embankment when a heavy truck crosses it.
Field Test of Polymer Modified Asphalt Concrete: Murphy Road to Lava Butte Section
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This report covers the construciton of open-graded asphalt concrete test sections using one conventional and three different polymerized binders. The binders were: 1) Chevron's conventional AC-20 as a control, 2) Elf Aquitane's Styrelf with SB polymer, 3) Asphalt Supply and Service's AC-20R with SBS polymer, and 4) Chevron's CA(P)-1 with DuPont's Elvan (EVA) polymer.
This report also includes a summary of: pre-construction conditions, pavement design, test results and methods, the condition of the road just after construction, and cost data.
Satisfactory pavements were made with all of the binders. There were no major design or construction related problems. Minor problems included: 1) Styrelf and AC-20R tended to migrate downward through the mix, 2) AC-20R, and to a lesser degree, Styrelf left deposits on the surface of transport equipment, 3) all polymerized binders presented some problems with mix sample collection and binder extraction. None of these miner problems slowed the progress of the paving, and most were solved with innovations in either equipment or technique.
In-Depth Study of Cold In-Place Recycled Pavement Performance Volume I
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Oregon has developed a mix design procedure for cold in-place recycled (CIR) asphalt concrete pavements. The procedure involves estimation of an initial emulsion content based on gradation of recycled asphalt pavement (RAP), asphalt content of RAP, and penetration and viscosity of recovered asphalt. When an estimated emulsion content is determined, Marshall-sized specimens are prepared for a range of emulsion contents with the range centered on the estimated emulsion content. Hveem and Marshall stability, resilient modulus, and index of retained modulus (IRM) tests are performed on the specimens and a design emulsion content is selected based upon these results. Because of variations in RAP properties, continual need for field adjustments, and the difficulty of interpreting mix property test results, only the estimation part of this procedure is currently implemented.
This paper describes the mix design procedure and presents lab results demonstrating the difficulty of choosing emulsion content based on Hveem and Marshall stability, resilient modulus and IRM. Data comparing design emulsion content with actual emulsion contents used in the field are presented. Selection of water content is discussed. Test results of mix properties monitored over time are presented, demonstrating the curing of the emulsion. Performance data for CIR pavements constructed from 1984 through 1988 are presented as well as initial results of an attempt to use lime during recycling to correct a stripped pavement. A construction and inspection manual is presented as a separate document (Volume II, FHWA, OR-RD-91-02B).
Significant findings as a result of this study include the following:
- Field performance of CIR has been good, with a few exceptions. Proper project selection is extremely important.
- Estimation procedures for determining emulsion content serve as a good starting point for field operations. Continual monitoring and adjustment of emulsion content is required in the field.
- It is difficult to relate Hveem and Marshall stability, resilient modulus, fatigue and IRM laboratory testing to field construction conditions for CIR.
- Mix property test results indicate that the stiffness and fatigue properties of recycled mixtures increase over a period of years.
- Addition of 1% and 2% lime to RAP from badly stripped pavement produced better IRM results than the RAP without lime.
- Review of existing projects suggests service lives for low volume roads of 6 to 8 years for CIR with chip seal when projects are properly selected.
In-Depth Study of Cold In-Place Recycled Pavement Performance Volume II
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This manual presents an overview of important project selection, design, construction, and inspection considerations for cold in-place recycled (CIR) asphalt mixtures. The first section summarizes the historical use of CIR mixtures. The second summarizes the construction process. The third section presents some of the important preconstruction steps (project selection, field sampling, and mix design). The fourth section deals with field quality control of the CIR process. The fifth section deals with overall quality assurance and post-construction evaluation. The final section summarizes the procedures which are critical to a successful CIR process. This manual is based on CIR design and construction as practiced by the Oregon Department of Transportation (ODOT) in 1990 using CMS-2s or HFE-150 as recycling agents and depths of 2 to 4 inches. This manual is not intended for use on projects involving full-depth reclamation. This manual provides the reader with the necessary background to successfully manage and inspect CIR projects as the process is practiced by the Oregon Department of Transportation.
Evaluation of Performance Based Approach for Determining Contribution of Environmental Factors to Pa
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State Legislation requires that cost responsibility studies be available for the 1991 and 1993 Legislative sessions. Part of this legislative requirement includes the need to reevaluate and establish a sound basis for the weight-mile tax. To be fair and equitable, this tax should reflect the relative contribution of environmental factors and traffic loading to pavement deterioration. Researchers at Oregon State University recently developed the computer program PBA (Performance Based Approach) for determination of the degree to which pavement deterioration is due to load and non-load related factors (Ordonez and Vinson, 1988). This program is based on the methodology developed by researchers at Purdue University (Fwa and Sinha, 1984) for the State of Indiana's cost allocation study. Evaluation of the PBA methodology and the ability to implement it within Oregon is required prior to attempting to use the method to determine pavement deterioration cost responsibilities.
Evaluation of Asphalt Additives: Lava Butte to Fremont Highway Junction - Final Report
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This report covers four year's performance of ten test sections using dense-graded hot mix asphalt concrete with these additives: Plus Ride mix containing granulated tire rubber, Arm-R-Shield modified asphalt containing ground and dissolved tire rubber, Fiber Pave polypropylene fibers, Boni Fibers polyester fibers, Pave Bond anti-stripping asphalt additive, lime as an anti-stripping aggregate treatment, and CA (P) -1 asphalt containing an EVA polymer. The control section used conventional AC-20 asphalt.
At the end of four years, none of the test sections performed better than the control. The only significant distresses were a slight loss of aggregate in the wheel tracks of the Plus Ride section and a comparatively large amount of wheel track and transverse cracking in the CA (P)-1 sections. None of this distress was severe enough to require repair.
The anti-stripping additives cannot be evaluated at this time, as no significant stripping has occurred on any section.
Distress measured on the roadway after four years was compared to the results of tests done on briquettes made out of mix sampled from behind the paver. The best correlations were: rutting vs. the 77˚ and 115˚ penetration, longitudinal wheel track cracking vs. the unconditioned diametral resilient modulus, transverse cracking vs. the 73˚ fatigue test results, and raveling and weathering vs. the index of retained strength and the freeze-thaw/unconditioned diametral resilient modulus ratio.
Evaluation of Bond-Controlled, Epoxy-Coated Prestressing Strand on Hubbard Creek Bridge - Final
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Oregon's many coastal bridges are subject to a severely corrosive environment, being exposed to frequent rain and fog and a nearly constant misting of salt spray. Heavy rains flush ocean salts off the sides and decks of bridges, but leave the underside covered with salty ocean spray. Because of this spray, coastal bridges are more subject to corrosive attack on the underside than from chlorides applied to the deck. A significant number of coastal bridges are succumbing to the effects of this harsh environment and will be in need of replacement over the next several years.
Pre-stressed concrete bridges will most likely be chosen to replace these deteriorating structures. Corrosive agents can attack the steel reinforcement contained in pre-stressed concrete structures, causing tensile stresses which fracture the concrete. Coating the reinforcing steel with epoxy encases and protects the steel from these corrosive agents.
While epoxy coated reinforcing steel has been used successfully to combat corrosion for several years, epoxy coating for pre-stressing strand is a relatively new development. An NCHRP study titled "Corrosion Protection of Pre-stressing Systems in Concrete Bridges" (Project 4-15, FY 1982) was conducted to test the mechanical behavior and corrosion resistance of epoxy coated 7-wire strand used in pre-stensioning applications. The final report for this study (NCHRP Report 313) concluded that epoxy coated pre-stressed strand was superior to bare strand wire in both corrosion resistance and bond strength. However, a full scale evaluation of girders in service in the appropriate environment, as opposed to laboratory tests and simulations, was considered essential.
Microsilica Modified Concrete for Bridge Deck Overlays - Construction Report
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The objective of this study is to see if microsilica concrete (MC) is a viable alternative to the latex modified concrete (LMC) usually used on bridge deck overlays in Oregon. This study addresses five MC overlays placed in 1989 on Portland cement concrete (PCC) bridge decks at three sites.
At each site the first MC pours had the most problems, as the contractors had no experience with the product. Most of the later pours went smoothly.
On most of the problem pours, the mixes were either too stiff as delivered or they started to lose slump too early in the placement and finishing process. Consequently, the MC was hard to finish and a poor quality overlay resulted. Solutions to this problem were: using mixes with higher slumps, delivery of consistent mix to the jobsite, adding most of the super-plasticizer at the jobsite rather than at the batch plant, and streamlining jobsite testing and mix adjustment.
If the mix was workable, the overlay could be mechanically finished. Otherwise, it was hand finished. Fogging was always needed.
Delamination and/or cracking was seen on some decks after several months of traffic. The cause of this distress is not known.
- Oregon is not presently known, MC overlays were constructed in this study that had adequate strength, a smooth uncracked surface, and minimal delamination, the same as LMC. Many of the problems observed in this study may be prevented by using the February 1990 or later specifications. Consequently, further use of MC is recommended as an alternative to LMC.
1. In some cases this may be an advantage over LMC.
2. The lower cost of furnishing MC is offset by higher construction costs.
3. MC overlays have higher initial skid resistances than typical LMC surfaces.
Evaluation of IMS - Swedish Laser Road Tester
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A test of the IMS - Swedish Laser road tester was conducted in September 1988. The vehicle mounted laser equipment was used to survey pavement conditions on sections of Oregon's Interstate and non-interstate highway system.
The IMS laser equipment performed in the manner expected, but deficiencies were noted in ground-point/mile marker location recording and in travel lane positioning.
The IMS equipment is able to gather large amounts of roadway data simultaneously.
The lack of present need for much of the data, however, does not make this method of data gathering cost effective for use on Oregon's highway system.
Long Term Deck Deterioration
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In May of 1981 the Oregon State Highway Division was asked by the Federal Highway Administration to participate in a long term deck deterioration study. The study, an extension on an earlier study that was finalized in 1979, was to run through 1990. Review of the data in 1987 made it apparent that further study would not produce any more meaningful information. FHWA was informed and agreed that further study was not warranted.
The Division chose seven bridges to monitor. Five of the bridges had membranes and two had test sections of epoxy coated rebar. Visual inspections were to be made annually and detailed inspections were scheduled for 1985 and 1990.
This summary report presents the work done from 1981 through 1987, including field tests, results and conclusions.