A Study of Oregon's Surfacing Design Procedures
Back to Top
This study of the Oregon State Highway Division's surfacing design procedures was undertaken to determine if the expected service is being obtained from current design practices, and to provide an economic comparison of different design alternatives to permit an optimum strategy to be selected. The economic analysis included full depth and staged construction alternatives for both 20 year and 10 year designs.
An analysis of deflection measurements taken for this study indicate that the predicted pavement performance is being achieved; however, none of the projects are old enough t o confirm the performance through the entire design life. There was some spread in the results, indicating some pavement performed better and some not as well as anticipated. The projects studied also showed that cracking and patching start to occur at the age the second stage overlay was expected to be needed.
The economic analysis of surfacing design alternatives indicated that a 20 year design life with the entire depth placed initially has the lowest total cost of the alternatives studied. The total cost over a 20 year period for a full depth 20 year design is about 20 percent lower than the cost for a 10 year full depth design and about 4 percent lower than the cost of a 20 year design with 2 inches delayed and placed when required. The analysis included an example of the affects of the alternatives on the backlog of poor pavements which indicated that for a 20 year period, the 20 year stage constructed design life would result in the lowest backlog.
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.
Energy Absorption of Gravel Mounds for Truck Escape Ramps
Back to Top
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.
Polymer Concrete Overlay Test Program Users' Manual
Back to Top
Since the late 1960’s, the major concern of bridge maintenance engineers has been bridge deck repairs. Highway departments across the country found bridge maintenance costs soaring as bridge decks deteriorated to an unsound condition. The use of deicing chemicals was identified as the chief cause of the premature deterioration. The corroding effects of these chemicals on unprotected decks caused the reinforcing steel to rust and the concrete to spall. As large potholes developed in the deck surfaces due to spalling, the structural adequacy of the decks diminished to a point where the decks were unsafe. Driving over the rough decks became an additional hazard.
Initial attempts to repair the damaged decks with conventional materials proved unsatisfactory. One major problem was the long curing time required to gain sufficient material strength. The prolonged closure of bridges or lanes of bridges, while repairs were made was found to be intolerable, especially in metropolitan areas.
As one avenue approaching this bridge deck repair problem, the Federal
Highway Administration commissioned the Oregon State Highway Division to investigate the use of a quick setting, high-early strength material called polymer concrete.
Recycling of Asphalt Concrete--Oregon's First Hot Mix Project
Back to Top
The needs to reduce fuel consumption and conserve natural resources have been items of ever-increasing importance during recent years. This report discusses a project in which almost 50,000 tons of asphalt concrete placed to carry detour traffic during a freeway reconstruction project were subsequently salvaged and recycled to overlay a section of State secondary highway. The material was stockpiled for about two years while plans for the pavement project were developed.
Assistance was provided by the Federal Highway Administration’s Demonstration Projects Division to subsidize the cost of some of the recycled asphalt concrete and to cover costs of evaluation for the project. The work was included under Demonstration Project No. 39, "Recycling Asphalt Pavements".
Evaluation of Rubber-Asphalt Chip Seals in Oregon
Back to Top
The Oregon State Highway Division, in cooperation with the Federal Highway Administration, participated in a demonstration project on the evaluation of rubber-asphalt chip seals. The trial projects were placed in Maintenance District 11, in the vicinity of Klamath Falls. The object of project was to give this type seal coat a working test. The process has been used for several years in Arizona. Sahuaro Petroleum of Phoenix, Arizona has been the major concern behind the process.
Two small sections of rubber-asphalt chip seal were placed in the Klamath Falls area in July of 1974. The performance obtained from these trial sections was very good. When FHWA provided the opportunity for Oregon to participate in the demonstration project program to provide a more extensive test of the process, District 11 requested that the work be done in that district.
Experimental Expansion Bearing Study
Back to Top
A study to evaluate the effectiveness and serviceability of bridge expansion bearings was undertaken by the Oregon State Highway Division in 1972. The evaluation was conducted under the provisions of the Experimental Features Program of the Federal Highway Administration. Initially, a work plan containing four bearing assemblies and outlining the proposed evaluation method was submitted to the Federal Highway Administration for inclusion in their Experimental Features Program. Subsequently, two additional bearing assemblies were added shortly after the study began.
To accomplish the evaluation, a detailed inspection of each bearing was specified to be performed by the Regional Bridge Inspectors on an annual basis. This inspection frequency was later changed to twice a year and specifically during the months of January and July in order to witness performance during extreme weather conditions. The data requested during each inspection included the following items:
- Condition of the bearing.
- Performance of the bearing.
- Specific repairs to the bearing.
- Ambient temperature and weather conditions during the inspection.
- Amount of bearing movement.
Experimental Deck Joint Seals - Final Report
Back to Top
The problems resulting from the failure to obtain durable watertight bridge deck joint seals prompted the Oregon State Highway Division in 1970 to participate in Project 11 of the National Experimental and Evaluation Program. This project was initiated to evaluate both proprietary and nonproprietary deck joint seals on a nationwide basis. Thirty-six states agreed to participate in this study, which promised to save maintenance costs of repairing bridge bearings and other structural elements due to non-functioning deck joint seals. Preventing the loss of esthetics because of unsightly water stains increased the appeal of this study.
In Oregon, the study of bridge deck joint seals consisted of semi-annual inspections of a select group of seals by regional bridge inspectors. These inspections were scheduled for times of extreme weather conditions. The joint seals selected for examination varied from nonproprietary single cell units to elaborate proprietary modular and reinforced molded units.
The Use and Effects of Studded Tires in Oregon
Back to Top
During the past 11 years the use of studded tires has increased from a novelty to an estimated average of 20 percent for the Northern States in which snow and ice is expected. An alarming amount of surface wear in the wheel paths of the highway pavements has accompanied the increase in studded tire use. In Oregon, the use of studded tires, first authorized in 1967, increased to a statewide average of 9.2 percent for the winter of 1973-74. Here, too, the surfaces are showing wear, particularly severe on highways carrying high traffic volumes.
Polymer Concrete Overlay Test Program
Back to Top
This report describes work done on various combinations of monomers and concrete mixes and identifies the mixes showing the greatest potential for use in bridge deck overlays. Presented are test results showing physical properties of various polymer concrete mixes, such as compressive strength, split tensile strength, modulus of elasticity, thermal coefficient of expansion, and shrinkage coefficient. The effects of polymer content, work time, and temperature on various properties are also discussed.
The development of two polymer concrete systems with excellent membrane potential are described along with the details of bonding characteristics of several systems.
Finally, a polymer concrete mix with suitable properties for deck and pavement patching is detailed.
Due to the positive results of the laboratory work on the polymer concrete overlay systems, an experimental field installation is recommended.
Experimental Expansion Bearing Study - Interim
Back to Top
The Oregon State Highway Division has undertaken an inspection program to gather data on several expansion devices. To date, six bearings have been included in the Category 2 Experimental Expansion Bearing Study. Three of the six bearings have been appraised as operating well, two have been found to be damaged and one was not evaluated since it had just been installed.
The information recorded during the inspections covered the amount of movement of the bearing, weather conditions during inspection, condition of the bearing and remarks pertinent to any repairs that were made or were to be made to the bearing. The inspections were scheduled during January and July in an attempt to record data during extreme weather conditions.
Experimental Dect Joint Seals - Interim
Back to Top
In 1971, the Oregon State Highway Division began to participate in the National Experimental and Evaluation Program (NEEP) Project No. 11 – “Development of Watertight Bridge Deck Joint Seals.” The purpose of this program was to evaluate several new proprietary bridge deck expansion joint seals which were claimed to prevent unsightly and structural damaging moisture leakage.
A work plan was developed whereby inspections were to be made at final inspection when the structure was completed, at six months after installation and annually thereafter for a minimum of three years. The latter requirement was changed to two annual inspections, specifically during the months of January and July. This change ensured inspections during extreme weather conditions.
The performance of the joints was rated in four general areas:
1. Did the joint leak?
2. Was the joint damaged?
3. Was the joint noisy under traffic?
4. What was the ride-ability quality?
Experimental Use of Flexible Guideposts in Oregon
Back to Top
During the early months of 1971 the Oregon State Highway Division requested and received FHWA approval to install flexible guideposts in locations where sight post losses from collisions would be expected to be high. The request was to install the flexible posts as an experimental feature under the provisions of PPM 20-6.3 as a Category 2 Project. Limited use of the posts was initiated in contracts let during the spring of 1971. When used, they were installed in exit gore areas and on interchange ramps having curvature of 11 degrees or more. Also, at flared and channelized intersections having heavy turning movements, flexible guideposts have been used to delineate the turning radii in each quadrant.
Polymer Concrete Development
Back to Top
Approximately eight years ago, a project was initiated at the suggestion of the Bureau of Reclamation to determine the effect of impregnating a cured concrete with a monomer followed by a radiation treatment to cause polymerization. The initial work impregnated concrete bars with gaseous and liquid monomers and used Cobalt 60 gamma radiation. Several remarkable improvements in properties were noted for the samples.
Demonstration of Visibility Measuring Device to Detect Highway Fog Conditions
Back to Top
This project is being conducted to evaluate a commercially available visibility measuring device (Impulsphysik, GmbH Videograph) as to its possible application in the field of traffic control under reduced visibility driving conditions. The evaluation consists of a comparison of the Videograph ranges with human visual range and the operating experiences with the equipment. The videograph is a back-scatter type transmissiometer.
Due to inadequate time periods of fog since the equipment was installed, valid conclusions are difficult to achieve; however, the data which has been collected indicates a fairly strong correlation between the indicated videograph ranges and human visual range and the equipment has been relatively trouble free. The major obstacle to its use as a control device appeared to be rapid changes in fog density which were encountered. These changes cause the videograph’s output to fluctuate in an unsatisfactory manner. Based upon these results, the tentative conclusions reached are that the videograph would not be practical for controlling the signs without the addition of visibility averaging equipment to dampen the fluctuation. A videograph with such equipment appears to have potential as an automatic control device and should be evaluated. The videograph may also have application as an advisory device and/or as an on-off sign system control.
Variable Message Fog Hazard Warning Signs to Control Vehicle Operating Characteristics
Back to Top
This project is aimed at determining the effectiveness of variable message signs in controlling traffic on an Interstate highway during periods of hazardous driving conditions such as fog, vehicle accidents, or congestion.
The effectiveness of the signs is being measured quantitatively by use of accident records, vehicular speeds, and headways. Insufficient data preclude drawing quantitative
conclusions; however, based on data available interviews with the state Police, and visual observation of vehicular operations it appears that the signs are effective in controlling traffic operations and thereby preventing accidents during periods of reduced visibility due to fog.
Temperature-Viscosity Relationships of Selected Asphalt Cements
Back to Top
It has been common to purchase asphalt cements for asphalt concrete construction by specifying the penetration grade and to further specify limiting values for flash point, solubility, ductility, thin film loss, and penetration of residue after thin film test. The penetration test is, of course, a measure of the consistency or viscosity at the test temperature of 77°F. The other tests assure a product free of contaminants and having suitable ductility and resistance to excessive hardening. None of these tests, however, provide a measure of the consistency of the asphalt cement at the elevated temperatures required for mixing, placing and rolling the asphalt concrete. It is known that two asphalts having the same penetration at 77°F may have significantly different viscosities at other temperatures. The viscosity of the asphalt during mixing, placing, and rolling is very important in obtaining a quality pavement. In most standards, limiting temperature ranges are specified for these operations but this control fails to distinguish between asphalts having widely varying high temperature viscosities.
Service Behavior of Asphalt Concrete - A Ten-Year Study
Back to Top
Surface conditions were evaluated and samples of asphalt concrete and stone base were obtained twice yearly for a ten year period at 32 test points on eight heavily traveled highways in Oregon. A stepwise linear regression analysis was conducted to determine relationships that exist between different pavement properties and between pavement properties and service characteristics of the pavement.
Variables of time and condition that were considered in the project included year service, equivalent wheel loads, a pavement condition code, and wheel track depressions. Properties of the asphalt concrete included in the regression analysis were specific gravity, relative compaction, percent air voids, stabilometer S values on in-place and re-compacted cores, cohesiometer values, penetration of recovered asphalt, asphalt content, relative compaction and gradation. Analysis of the asphalt concrete included samples of both base lift and top lift of pavement at locations in the wheel track and in the adjacent shoulder.
Although the stabilometer S values for the in-place material were typically low (usually 15-25) there was in evidence of pavement instability. The regression equations show that for these mixes the pavement service becomes worse as the stabilometer values increase, indicating stability may be over emphasized at the cost of reduced flexibility. The study tends to confirm and to emphasize many acce4pted relations regarding pavement performance but also, some relationships are indicated by the equations that have not been widely recognized in the past. These indications may aid in the quest for more durable pavements.
Manzanita Safety Rest Area Sewage Disposal Facility - Summary Report
Back to Top
The existing sewage disposal facility at the Manzanita Safety Rest Area was authorized as a Category 2 Experimental Project by FHWA on August 9, 1972. The purpose of this experimental project was to determine, by actual use, the feasibility of utilizing a self-contained chemical-physical sewage disposal system in remote locations such as safety rest areas and state parks where subsurface disposal is environmentally unacceptable.
Under an agreement dated November 30, 1972, the State employed Wasteco Inc., and Chem-Pure West, I n c., (Contractor) to provide a self-contained chemical-physical unit at Manzanita Safety Rest Area. The agreement was supplemented in 1974 and 1977 to implement needed design changes in an attempt to provide a functionally satisfactory facility. The facility was initially completed and put into operation on September 11, 1974.