| Abstract XVII |
 |
|
|
 |
| Recycled Pavement |
|
In-Depth Study of Cold In-Place Recycled Pavement Performance Vol I
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.
|
|
|
| Deck Deterioration |
|
Long Term Deck Deterioration
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.
|
|
|
| Asphalt Pavement Recycling |
|
Woodburn Hot In-Plant Asphalt Pavement Recycling Project
In 1977, the Oregon Department of Transportation constructed a demonstration project using approximately 47,000 tons of stockpiled asphalt concrete (AC) material to overlay a section of pavement in Oregon. The stockpiled AC material was hot in-plant recycled and paved as a conventional hot AC mix. For twelve years of service, the hot in-plant recycled pavement performed well and carried traffic well in excess of the design loadings.
The construction details of this demonstration project were documented in an interim report published in 1977. This final report provides various information regarding the project, including the design, construction, and performance of the recycled AC pavement.
Based upon the design, construction, and performance of this project, the following conclusions were drawn:
- Asphalt concrete material can be hot in-plant recycled and reused for surface paving. 2) The properties of slightly aged asphalt cement can be adequately modified through the addition of new "soft" asphalt cements without the incorporation of recycling additives.
- Emissions in recycling are a function of many factors, including mix temperature, grade of new asphalt being added, amount of new aggregate added, amount of water added, and plant production rate.
- Variability in the material properties may be expected. The additions of new asphalt and aggregate may further increase the variability.
- Cost savings and conservation of natural resources can be expected due to the use of the recycled AC materials.
- The new hot in-plant recycled pavement surface was rougher than average new AC pavements.
- The pavement performed well and carried traffic well in excess of the design loadings.
|
|
|
| Antistripping Additives |
|
Effectiveness of Antistripping Additives Volume II
Volume I of the report summarizes the findings on the extent of stripping in 32 Oregon DOT projects and discusses the significant findings from a literature review. Of the 32 projects, 10 had not used an asphalt or aggregate anti-stripping additive, 19 contained lime-treated aggregate, and 3 contained asphalt treated with an amine-type anti-stripping additive. These projects range in age from 1-9 years. The percent of aggregate coated with asphalt, which was used to determine if a project was stripping, was established from breaking and visually evaluating core samples taken from each project site. Using the criteria that a coating less than 85% classified a project as stripping, the following results were obtained: 7 of the 10 projects without an additive, 5 of the 19 lime-treated aggregate projects, and 2 of the 3 amine-treated asphalt projects were identified as stripping. The conclusion is that lime treatment of aggregate has proven effective in reducing the moisture susceptinility of an asphalt mixture. In addition, a review of mix design test values for the index of retained strength (IRS) (AASHTO T-165) and resilient modulus (Mŗ) test indicates the IRS test does not reliably predict moisture susceptible mixtures. The Mŗ test did provide a better indication of moisture susceptible mixtures. This assessment is based on a limited amount of data and is not statistically based; therefore, the results may change with further information. Volume II presents the complete literature review.
|
|
|
| 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.
|
|
|
| Energy Absorption |
|
Energy Absorption of Gravel Mounds for Truck Escape Ramps
Escape ramps, used to stop trucks that have had brake failure on long downhill grades, are usually constructed in terrain where an ascending grade can be utilized to assist in stopping the vehicles. An arrester bed of non-compacting gravel is typically used to stopping the truck and to prevent rollback of trucks after having stopped. In terrain where an ascending grade is not available and the length available for ramp construction is limited, other energy absorbing means are needed. Some use has been made of gravel mounds at the end of escape ramps as an emergency measure to stop vehicles not stopped by the arrester bed. Documentation of the reaction of trucks striking these gravel mounds is very limited. The purpose of this study was to evaluate the reaction of trucks impacting transverse gravel mounds.
Mounds 1 foot, 2 feet, and 2.5 feet were tested singly and in groups of three. The test vehicles were two-axle dump trucks loaded with gravel. Test speeds were generally at 25 mph and 40 mph. The higher mounds were effective in slowing the truck without driver injury but truck damage in the form of bent tie rods was common and the front axles were bent on several trucks.
Transverse gravel mounds are not recommended for truck escape ramps except in critical circumstances.
|
|
|
| Layer Coefficients |
|
Establishing Layer Coefficients for CTB, PMBB, and RAP
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.
|
|
|
| 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.
|
|
|
| Eugene Sand & Gravel |
|
Eugene Sand & Gravel High-Strength Concrete Report Study
This research study was undertaken in response to the production of substandard high-strength concrete by the Eugene Sand and Gravel Company on three separate highway construction contracts (five separate bridge structures). The routine testing of concrete cylinders collected for acceptance testing indicated that the concrete did not meet the minimum strength requirements specified for the contracts. Table 1 summarizes the test results which document the substandard concrete strengths.
In reviewing the test results with the concrete supplier, the validity of the results were challenged because plastic cylinder molds were used on some of the projects instead of the steel cylinder molds customarily used by Eugene Sand and Gravel (ESCG), Questions were also raised about the method of transport of concrete cylinders to the Oregon State Highway Division (OSHD) Materials Laboratory.
This research study was undertaken to determine the effect of different test variables such as mold type, method of transport, method of sealing, and type of test equipment of tested concrete cylinder strength.
|
|
|
| Bent Caps |
|
Evaluation of Bent Caps in Reinforced Concrete Deck Girder Bridges
This report describes research conducted to enable evaluation of existing vintage bent cap beams in reinforced concrete deck girder bridges. The report is organized into two parts: 1) flexural anchorage capacity response and prediction of reduced development length due to beneficial column axial compression and 2) structural performance of bent cap systems and their analytical evaluation. Each of these parts including descriptions of the experimental specimens and results of analytical studies is described separately. The research results from both studies are combined and used in an example to demonstrate the rating of an actual 1950’s vintage RCDG bent cap beam for continuous and single trip permit loads.
|
|
|
| Keystone/Tensar Geogrid |
|
Evaluation of a Keystone/Tensar Geogrid Retaining Wall System
The KeyStone/Tensar Geogrid retaining wall system is an alternative to conventional reinforced concrete retaining wall structures. Keystone concrete wall units, Tensar geogrid, and compacted soils are combined to form a reinforced soil mass that together act as a gravity wall structure to resist lateral earth pressures and surcharge loads.
The objective of this experimental features project is to evaluate the construction and performance of the KeyStone/Tensar retaining wall system. The benefits, as stated by the manufacturer, of this wall system include: design flexibility, easy installation, cost efficient, beauty, and wall face drainage properties.
The features of this wall system that were evaluated include: construction (including installation times and labor costs), quality and availability of pre-cast elements, wall costs, aesthetics, wall stability and performance, and appropriateness of design details and parameters.
Two walls located in Portland, Oregon were evaluated as part of this research. Wall 1 is approximately 183 feet long, facing Southwest Taylors Ferry Road. The wall has multiple footing steps to accommodate the roadway grade and ranges in height from approximately 2.5 feet to 16 feet. Wall 2 is approximately 190 feet long, fronting on Southwest Bertha Boulevard. The wall has one footing step to accommodate roadway grade and ranges in height from 2.5 feet to 6.5 feet.
The KeyStone/Tensar geogrid retaining walls evaluated as a part of this project have performed well for two years. Although problems were encountered with block placement during construction of the walls, these problems can be avoided in future projects by designing footing and block placement with consideration of horizontal growth, batter due to block setback and thickness of geogrid.
Even though costs were not substantially lower than the estimate for conventional reinforced concrete retaining wall structures, the aesthetic qualities, performance, and construction time make this type of wall an acceptable alternative. Therefore, it is recommended that the KeyStone/Tensar Geogrid retaining wall system be considered as an acceptable alternative to conventional retaining walls for similar installations. Full acceptance of this retaining wall system for use on State projects will require completion of the OSHD Bridge Section's "Wall Acceptance Procedures;" these acceptance procedures are currently being developed.
|
|
|
| Bond-Controlled, Epoxy Coated Interim |
|
Evaluation of Bond-Controlled, Epoxy-Coated Prestressing Strand on Hubbard Creek Bridge Interim
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 undersides 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. A NCHRP study "Corrosion Protection of Pre-stressing Systems in Concrete Bridges" (Project 4-15, FY '82) is currently underway to test the mechanical behavior and corrosion resistance of epoxy coated 7-wire strand used in pre-tensioning applications. However, an evaluation of actual girders in service in t he appropriate environment, as opposed to laboratory tests and simulations, was considered essential.
|
|
|
| Piezoelectric Weigh-In-Motion |
|
Low-Cost Piezoelectric Weigh-In-Motion Systems in Oregon: 1988-1993
In 1988, The Oregon Department of Transportation installed low-cost piezoelectric weigh-in-motion cables at three locations and in ten lanes on Interstate 5 and 205. This report documents the installation of the systems, problems, and results from 1988 to 1993.
The findings show that these systems are sensitive to pavement temperatures and need to be auto-calibrated. Their accuracies vary according to the pavement condition and type. Multi-sensor piezoelectric weigh-in-motion systems were evaluated with respect to improving accuracy. The results show that multi-sensors do improve weight accuracies. These systems should be used only in moderate to low traffic volume roads, rather than on the interstate or primary highways, and primarily for data collection purposes.
|
|
|
| Bond-Controlled, Epoxy-Coated Final |
|
Evaluation of Bond-Controlled, Epoxy-Coated Prestressing Strand on Hubbard Creek Bridge
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.
|
|
|
| Baladi Indirect Tensile |
|
Evaluation of the Baladi Indirect Tensile Test Apparatus
Dr. Gilbert Baladi, of Michigan State University, has designed an indirect tensile test device to measure certain characteristics of asphalt concrete. The Oregon Department of Transportation currently uses the Retsina Mark VI device to measure the modulus of resiliency of A/C, and is participating in a study that compares the MŘ test results of the two devices. This report gives a brief description of the two systems, the test procedure, the results obtained by each and a statistical analysis of those results.
Eleven calibration specimens and over thirty asphalt briquette specimens were tested with varying degrees of success and failure. Representative results are presented in tables one through three, which also show the variance from the mean MŘ, prints depicting the horizontal deformation of some specimens (recorded with the ATS Scope Program) are included (figures 1-16). These show the uneven horizontal deformation experienced in Dr. Baladi’s device. Tables A-D present the statistical analysis.
In conclusion, the Retsina Mark VI System is the easier to operate of the two; but the Baladi device (run by the ATS Software) is superior in data collection, storage and retrieval. The Baladi device operated erratically and needs improvement before further comparison can be done.
|
|
|
| Diamond Barricades |
|
Evaluation of Diamond Barricades in Construction Zones
Experimental diamond barricades, developed by the Federal Highway Administration, were deployed and evaluated on two construction projects in Oregon. The diamond barricades, types II and III were fabricated by the state sign shop and were installed in place of standard striped barricades at typical work zone lane closures, one on an interstate freeway, the other on an urban arterial highway. Observations and measurements of traffic flow characteristics were made in an effort to compare the two barricade designs and to identify any potential deficiencies in the diamond barricades.
Data obtained from vehicle speed and lane change measurements did not conclusively prove either barricade type to be superior to the other. As a traffic control device, both panel designs were equally effective. Traffic conflict and erratic maneuver rates, on the other hand, were significantly lower for the diamond barricades at the urban site.
No particular problems were found in the barricade fabrication process. If the barricades were to be made a standard, production costs would not increase over the current cost of producing striped barricades, except for costs associated with larger panel sizes. In the field, the diamond barricades were found to be more visible than the striped barricades, due to an increased panel width (8" t o 129, as well as the tendency of the diamond pattern to stand out from the background better than the striped pattern. The overall performance of the diamond panel in these tests indicates that it is an acceptable alternative to the striped panel design f o r use on barricade rails.
|
|
|
| Continuously Reinforced Pavement |
|
Condition Monitoring of Continuously Reinforced Concrete Pavement
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.
|
|
|
| Construction and Short-term |
|
Evaluation of Construction and Short-Term Performance Problems for Asphalt Pavements in Oregon
During the three-year period from 1974 to 1977, an increased occurrence of asphalt concrete pavement problems were noted throughout the United States during and after construction. In Oregon, construction and performance problems that were seldom experience prior to 1974 developed, and include:
(1) Incompactible mixes,
(2) Slow setting mixes,
(3) Flushing mixes,
(4) Low mix cohesion, and
(5) High incidence of ''blue smoke" during mixing and lay down.
In an effort to determine the causes of these problems, questionnaires were sent to regional and field construction engineers in 1975 and 1976 to establish the type and extent of problems and to collect information for each job, such as construction procedures, material properties, and mix designs, which may be related to the observed problems. Based on these results, fourteen projects with and without problems were selected for additional study and evaluation. These evaluations included:
(1) Conducting performance surveys,
(2) Obtaining cores of good and bad sections,
(3) Performing test on the mixes, and
(4) Performing tests on the asphalt.
This report summarizes the results of the questionnaire, field survey and laboratory testing. Analysis of the results indicates:
(1) Many of the reported problems in Oregon were due to extreme variations in material properties, such as high fines, high asphalt content, and low asphalt viscosity.
(2) Variations in asphalt temperature susceptibility between grade and between suppliers, as well as use of drum dryer type paving plants and in consistent addition of dust collector materials may also have contributed to the observed variations in material properties.
The study addresses a significant problem which has been observed throughout the United States. Hopefully, it will indicate to others that many factors can contribute to construction and performance problems and that all factors need to be carefully considered.
|
|
| |
|
|
