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Research Report Abstracts

Asphalt Aging in Hot Mix Plants

Recent Evaluation of Asphalt Aging in Hot Mix Plants 1983-1985 "C" Value Data

Starting in 1981 and continuing through July of 1983 “C” value data were col1ected from 29 different projects in Oregon.  Results from the study indicated that the overall operation and construction of asphalt plants, burner fuel type, mixing temperature and the use of bag house dust collectors had a significant inf1uence on the tenderness of the produced mix.  The results were published in a 1984 report (Lurid and Wilson, 1984).
 
In 1985, “C” values were again ana1yzed to see if any changes had occurred since the 1981-1983 study.  Forty-nine projects constructed or under construction from August 1983 to July 1985 were reviewed, from which 193 individual “C” values were obtained.  Comparing the results with the 1981-1983 data, indicated that individual variables such as burner fuel type, dust collection system, and plant type no longer are associated with changes in “C” values.  Instead the entire operation (adjustment) of the asphalt plant is the major influence on the “C” value.  Due to plant adjustments, several contracts, having poor results in the past, have been able to raise their average “C” value.
 


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Projects on Asphalt Aging

Evaluation of Questionnaire for 1981-1983 Projects on Asphalt Aging in Hot Mix Plants
As a measure of the aging of asphalt concrete mixes in the mixing and placement process, a formula was developed to determine the percentage of expected change in asphalt viscosity at the time of paving (Lund and Wilson, 1984). A value of 30 or higher was used in 1983-84 for acceptance on paving projects. At the conclusion of this study, a follow-up survey was made of all projects. Two major areas of interest were covered in the follow-up questionnaire: 1) the characteristics of the asphalt mix and pavement at the time of placement, and 2) the characteristics of the pavement at the time of receiving the questionnaire (March, 1984).
 
The responses to the questionnaire, even though they are subjective, appear to identify and confirm relationships between the "C" value and asphalt mix problems. The strongest correlation appears to be more with problems at the time of construction than with long term pavement performance problems. Using statistical tests, the significant problems that were identified during construction were tenderness, shoving and rutting, segregation and the mix being too cold. The long term significant problems developing after construction were stripping and cracking.
 
When the individual characteristics were evaluated, the great majority had the significance level peak at the less than 40 "C" value.  This is, a greater percentage of the samples that are below 40 have some problems in the field.
 
In early 1985, the Oregon Highway Department raised the minimum acceptable "C" value to 40. Mix with a value less than 40 is to be removed, or at the discretion of the Engineer, it may be left in place and a reduction in a Composite Pay Factor calculated (OSHD Spec. 403.39).


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Stabilometer "S" Value

Stabilometer "S" Value Study on Asphalt Concrete Samples

During the late fall of 1969, a study was made to determine the precision when testing asphalt concrete specimens for the Hveem stabilometer ("S") value (AASHTO T 246).  Fifty samples, using Chevron 85-100 asphalt cement and aggregate from Walling Sand and Gravel (Salem Blacktop), were prepared at each of five asphalt contents. The asphalt contents ranged from 5.0 to 7.0 percent at 0.5 percent increments.
 
Both first compaction and second compaction were determined as well as "S" value and bulk specific gravity. The first compaction is to simulate field conditions at the time of construction and the second approximating long term conditions due to further densification from traffic.


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Stabilometer "S" Comparison

Stabilometer "S" Value Comparison Using Anti-Stripping Additives

From January through July, 1985, asphalt mixes from five construction projects, with and without an anti-stripping additive, were compared for stability. Ten mix samples for each project, at varying asphalt cement content, were prepared and tested in the Hveem stabilometer ("S" value). Both first and second compaction results were determined. A table of the data appears in the Appendix.
 
The anti-stripping additive was 0.5% Pave Bond Special for all samples. The asphalt cements were Chevron AR4000W for three projects, Chevron AC 20 for one, and Sound AR4000W on the fifth project.


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Blowing Dust Alarm

An Experimental Blowing Dust Alarm System for Highways
Blowing dust storms pose a visibility hazard to highway motorists.  An experimental alarm which senses electrification of a metal antenna by blowing dust particles is described.  The metal antenna can be an ordinary radio whip antenna or an insulated top strand of barbed-wire right of way fence to monitor a greater area.  The sensor responded favorably under conditions of half mile visibility and 20 mph winds.  Field tests were conducted by telemetry to an office microcomputer.
 
Dust related radio noise which blanks out broadcast reception is attributed to electrification of metallic objects and subsequent corona or spark discharge.
 
An experimental acoustic sensor for flowing sand is also described along with comment on application of an ionization chamber to detect motionless dust.


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Shale Embankment

Shale Embankment Construction Criteria
Considering past problems encountered in construction of embankments using coastal shales, state highway engineers decided to conduct a study to evaluate the performance of shale as a fill embankment material and to assess its strength, compressibility and settlement characteristics.
 
The research was conducted in the summer of 1983 during the realignment construction of the Mystic Creek - Camas Valley section on the Coos Bay - Roseburg Highway.


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Flexible Pavement Phase 2

Identification and Quantification of the Extent of Asphalt Stripping in Flexible Pavements in Oregon Phase 2

This report is the second phase of a study in Oregon to evaluate the effect of material sources, void content, and additive type on retained strength (AASHTO T-165) or retained modulus (NCHRP Report 192).  A total of 20 projects were evaluated in the laboratory as a part of Phase I.  The results clearly indicated that material and additive type affect asphalt aggregate interaction.
 
The results of Phase II are presented herein.  A total of 8 of the Phase I projects were sampled and tested for: 1) mix properties, and 2) asphalt and aggregate properties.  The results of Phase II indicate: 1) there is evidence the IRS and modulus ratios correlate with field performance; 2) there is substantial variation in IRS and modulus ratios between the mix design and field cores; and 3) the-long-term effects of additives need to be determined.


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Geogrid Reinforced Soil Wall

A Geogrid Reinforced Soil Wall for Landslide Correction on the Oregon Coast

In June and July 1983, the Oregon State Highway Division constructed a geogrid retained soil wall to stabilize a landslide on the Oregon Coast.  The project was a Federal Highway Administration Experimental Features Project.  The experimental aspects of the project were to assess construction problems of near vertical walls with high density polyethylene geogrids and to investigate the feasibility of establishing vegetation on the wall face to provide a natural appearance at an esthetically sensitive site.
 
This report presents the experience gained in the design and construction of the geogrid wall. Problems encountered during construction are discussed and recommendations are made for improved methods for future application.
 
It is concluded that geogrid wall construction is practical. Geogrids are more labor intensive than conventional geotextiles, but their greater strength and ultraviolet light resistance are compensating advantages.  Establishment of vegetation on the face of a geogrid wall is possible by placing sod strips between the backfill and the geogrid. Care must be provided, however, to properly irrigate the sod until it is well established.  A coarse backfill or a filter fabric should be used if sod is not placed against the face to limit the loss of fines.


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Deck Overlay

Deck Overlay Firestone Rub-R-Road
During the fall of 1979, the Interstate Bridge, which spans the Columbia River carrying I-5 between Oregon and Washington, was overlayed with Rub-R-Road, a rubberized (latex-reinforced) asphalt concrete.  Rub-R-Road, developed by Rub-R-Road, Inc. of Akron, Ohio, uses an asphalt cement which is 5% latex by weight.
 
A 1977 report entitles “Membrane Waterproofing for Bridge Decks,” prepared by William Quinn, Oregon State Highway Division, Research Section, reported that Rub-R-Road failed the testing for use as a waterproofing membrane for bridge decks.  However, it was noted in the report that because the membranes were beneath an asphalt concrete wearing course, the electrical resistivity test used as the pass-fail criterion was unreliable, the reason being once the asphalt concrete overlay becomes saturated with water, the resistance test can be short circuited around the edge of the membrane resulting in erroneous measurements.  The performance of Rub-R-Road as a waterproofing membrane was, therefore, not reliably established.


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Verglimit

Verglimit
Bridge deck icing is a phenomena that Highway Departments and motorists must contend with each winter. The formation of ice on bridge decks as the temperature falls below 0ºC (32º F) creates a particularly treacherous condition.  Since much less heat is stored in the deck than in the ground, the deck can ice while the rest of the roadway is clear.  When this occurs, unwary drivers may approach these bridges at unsafe speeds.
 
Verglimit is the proprietary name for a multi-component defroster that is added to the asphalt concrete wearing surface.  It is a specifically conserved and activated defroster compound which is released in small quantities by the traffic induced abrasion.  Verglimit, which is produced in Germany, has been primarily used in Europe.  In view of the favorable reports from Europe, it was decided to test it on two bridges in Oregon that are known to have icing problems.


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Retention Factor

Evaluation of Retention Factor and Moisture Correction for Determining Asphalt Content in Asphalt Content in Asphalt Concrete Mixtures
 
This report was undertaken as a result of the recommendation from the "Comparison of Sampling and Test Methods for Determining Asphalt Content and Moisture Correction in Asphalt Concrete Mixtures" report.  For asphalt concrete mixture the OSHD Materials Laboratory compared three sources of aggregate, two methods of determining moisture content, and the differences in added asphalt and the extracted asphalt quantities.


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Stress Absorbing Membrane

Stress Absorbing Membrane Innerlayer

The westbound lanes of the South Baker Interchange-Encina Interchange Section of 1-84 were overlayed in 1977. A stress absorbing membrane innerlayer (SAMI), was included in this overlay as an experimental feature.  This report is the final evaluation of the SAMI.


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Content and Moisture Correct

Comparison of Sampling and Test Methods for Determining Asphalt Content and Moisture Correction in Asphalt Concrete Mixtures
 
Concerns have been expressed by the Oregon Asphalt Paving Association regarding the reliability of sampling and test procedures used by OSHD to determine the asphalt content and gradation of asphalt concrete mixtures. In response to these concerns an evaluation of OSHD sampling procedures, method of moisture determination, and asphalt content were undertaken.  The OSHD Materials Laboratory in cooperation with W. Reid Meritt, Project Manager of the Moro-Grass Valley Contract, and Frank D. Morrison, Project Manager of the Powers Jct.-Shields Contract, compared two methods of sampling and four methods of determining moisture content of asphalt concrete mixtures.


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Latex Modified Concrete

Latex Modified Fibrous Concrete

In November 1980, a contractor requested permission to use a 1.5 inch thick Latex Modified Fibrous Concrete (LMFC) overlay in lieu of a 2.5 inch low slump concrete (Iowa System) or a 2.5 inch un-reinforced latex modified concrete. The overlays were to be on four bridge decks within the Sundial - Sandy River Section.
 
At the time the request was made, the contractor gave a presentation to state engineers on the benefits of using this new material. He pointed out the LMFC was reported to reduce reflective cracking in previously placed deck overlays. Since
Oregon was having problems in this area, conditional approval was granted by the engineers.
 
The Latex Modified Fibrous Concrete used consisted of approximately 85 lbs. of steel fibers per cubic yard of 8 sack latex modified concrete. The 1 1/2 inch overlay thickness was permitted due to the reported greater flexural strength of latex modified concrete with fiber. The steel fibers used were Dramix ZP 50/.50.
 
Before the project began, laboratory work was identified that would be required before construction. This report discusses the results of that laboratory study, the construction techniques used, the major problems encountered during construction and the results of six post construction inspections.


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Pavement Management-Interim Report

A Pavement Management Research Program for Oregon Highways Interim Report 

This is the first in a series of reports documenting progress on a statewide pavement management research project.  The overall project is conducting research into pavement life cycles of different rehabilitation treatments; the cost-effectiveness of each treatment; and, the use of objective pavement condition data such as roughness, skid resistance, deflection, percent cracks, percent patches, and rut depth in a statewide pavement management system.
 
This report describes the project history and previous work conducted to date, as well as the scope of work of the present project.  A brief discussion of literature review results is provided.
 
The major emphasis of this report is a description of the pavement deflection data collection program-a statewide effort which monitors more than 1000 test sites once every two years. Data collected for the correlation of Benkelman beam deflection to Dynaflect deflection is analyzed and an equation relating the two is proposed for use in Oregon. Data collected for developing a Dynaflect deflection temperature correction factor (normalized to 70º Fahrenheit) is described.


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Protective Coatings

Protective Coatings on Concrete Surfaces Madden Macryseal

The intrusion of salt-laden moisture into concrete bridge members has caused considerable damage to bridges along the Oregon coast.  The increasing chloride ion content of the concrete fosters a galvanic corrosion cell.  This results in the rapid corrosion of the reinforcing steel and the spalling of the concrete.   To prevent the intrusion of chloride ions into the concrete, the Oregon State Highway Division specifications call for a concrete sealer on select concrete members on coastal bridges.
 
When the Yachats River Bridge (on US 101 in Lincoln County, Oregon) was constructed in 1977, the contractor requested permission to use Macryseal, supplied by Madden Construction Supply (Portland, Oregon).  Since Macryseal was not an approved sealer, preliminary tests were done by the Research Section of the Oregon State Highway Division.  These tests indicated that Macryseal provided protection that was comparable to that provided by the sealers already approved.  Therefore, permission was granted to use Macryseal and a program to evaluate its performance was scheduled. 
 
The Yachats River Bridge carries two lanes of traffic on a 2-1/2 inch asphalt concrete wearing surface. The bridge is 223 feet long and consists of two pre-stressed concrete slab approach spans and a pre-stressed concrete bulb-T main span. The Pacific Ocean (the breakers are only several hundred yards away) provides a salt-rich spray which coats the bridge.


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Resilient Modulus Test

Application of Resilient Modulus Test Equipment and Procedures for Subgrade Soils
 
This report is the first part of a two-part series.  It describes the techniques involved in, and the results from, resilient modulus testing of subgrade soils that are typically found in Oregon.  Two methods of testing were investigated:  the triaxial and diametral repeated load procedures.  Subgrade soils obtained from two projects were tested.  One project was a new alignment construction project in the Willamette Valley (Salem Parkway) for which there were two distinct subgrade soils (AASHTO classifications A-7-6 and A-4), the other was an overlay project in Central Oregon with a pumiceous subgrade soil (AASHTO classification A-1-b).  All other materials occurring in each pavement were tested at their in situ compositions, such that sufficient resilient modulus data was obtained for analyses and designs to be accomplished for each project.
 
It was found that the diametral testing procedure was adequate for use with cohesive soils, typical of those occurring in the Willamette Valley, but it is not recommended for use with the noncohesive volcanic soils occurring in Central Oregon.  For such soils the triaxial testing mode is recommended.  The major advantage of the diametral test for treated materials is its simplicity compared to the triaxial test.  However, the necessity to consider the effects of confining pressure for untreated soils diminishes this advantage, and with cohesionless soils the test is no simpler than the triaxial test, which is preferable for modeling the in situ stress regime.
 
The second part of this report (Part 2) presents procedures for analysis and design of flexible pavements, utilizing the results of the materials testing reported in Part 1.  The two projects investigated in this study were used to show how the current procedures used for design of new pavements and overlays in Oregon, can be supplemented by analytically based procedures.
 


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Polymer Concrete Overlay Final

Type A Polymer Concrete Overlay Field Trials
This report describes placement and subsequent performance of two methyl methacrylate polymer concrete overlays.  Performance is evaluated as to:
 

  1. the mixing and placement characteristics of the methyl methacrylate polymer concretes as overlay materials,
  2. the durability, skid resistance, impermeability and crack susceptibility of the materials in bridge wearing course construction and
  3. the preparation of the deck surface using an airless shotblast machine.
 
Both overlays performed well over a two year period; however, it is concluded that acceptance of the polymer concrete process will be slow because it is labor intensive.


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