Evaluation of PBA-6GR Binder for Open-Graded Asphalt Concrete
This report covers construction of open-graded asphalt concrete ("F" Mix) pavements with an asphalt-rubber binder, PBA-6GR. The PBA-6GR is manufactured at a refinery and delivered to the jobsite like conventional asphalt cement. Test sections and control sections were constructed in the fall of 1993, and summer and fall of 1994. One site is located in central Oregon on the Warm Springs Highway, US Route 26; the second site is located on Interstate 84 near Boardman; and the third site is located on Interstate 5, north of Grants Pass.
The PBA-6GR binder specifications are the same as the PBA-6 conventional asphalt specifications with the following exceptions: the kinematic viscosity on the original binder specification and the ductility test on the rolling thin film oven aged residue specification were deleted, following a written request by the contractor, as allowed in the Special Provisions.
Conventional open-graded mix design procedures were used to determine the optimal asphalt binder content. Since the binder did not drain down like PBA-6, analysis of void content and voids filled with asphalt (VFA) were used for binder content determination.
Construction of the asphalt-rubber mix progressed smoothly and the mix appeared to be easier to handle than the asphalt concrete with PBA-6 binders. The binder was not sticky and stringy; it did not collect on the truck dump gates; it did not allow the paver to settle into the mat during delays; it did not shove laterally during compaction; and it did not separate at higher temperatures. The mix was also easier to handle than other types of asphalt-rubber mixes. The contractor needed no extra mixing and handling equipment.
The asphalt-rubber mix cost per ton was 16% more that the "F" mixes constructed with PBA-6. When compared to 1994 bid prices, for "F" mixes, however, the PBA-6GR mix costs were 12% more. Advantages of the PBA-6GR mix, such as thick films, ease in construction, and ease in handling, may mike the binder preferable to conventional PBA-6.
Additional testing is needed to evaluate a proper mix design. Also, the Brookfield viscometer should be evaluated as a means to determine the temperature viscosity properties of the binder. The determine the cold temperature properties of the binder, the SHRP Bending Beam Rheometer should be evaluated. This binder would be suitable for use the meet the ISTEA rubber content mandate.
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Brugg Cable Mesh Rockfall Fence Final Report
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In 1991 a Brugg Cable Mesh Rockfall Fence was installed along Interstate 84 (I-84) 52 miles (84km) east of Portland to prevent large boulders, that roll down the 1500-foot (460 m) long talus slope of Shellrock Mountain, from entering the travel lanes. This was one of the first major installations of this fence on an Interstate Highway and was an FHWA experimental features project.
The Brugg Cable Mesh Rockfall Fence was selected for this site because it was the most cost effective and visually acceptable option that could be built on top of the existing bin wall. Also, because it could efficiently stop the large boulders that entered the travel lanes approximately every three years with the incorporation of a friction brake energy dissipater. During design, the standard tie-back anchors were eliminated to prevent damaging the talus slope and the Historic Columbia River Highway.
This was the first instillation of the fence both for ODOT and the contractor. Both considered construction very simple except for difficulties spray painting the fence on site due to the high winds. It was found that during design it is critical to have an accurate ground profile along the fence line to prevent changes during construction.
On August 8, 1992 a 1.7-ton (1.5-metric ton) boulder impacted a 6.5-foot (2.0 m) high mesh section three feet (0.9m) from a post. The fence stopped the boulder, however, the post and foundation rotated 20 degrees due to the foundations inability to resist the impact moment without the tie-backs. The velocity of the rock at impact was estimated to be 33 feet/second (10 m/sec) and the kinetic energy was approximately 66,000 foot-ponds (89,000 joules). The damage to the fence from this event was minor and has been repaired.
In the winter of 1993-1994, a 750-pound (340 kg) boulder impacted the second from the last mesh section, one foot (0.3 m) from the top. It resulted in only superficial damage not requiring repair.
Evaluation of Grit-Impregnated, Epoxy Coated Prestressing Strand on South Slough (Charleston) Bridge
The use of grit-impregnated, epoxy coated pre-stressing strand is a relatively new design strategy being used for corrosion abatement on new concrete structures. This application was chosen for the South Slough (Charleston) structure because it is subject to a corrosive environment created by the salt in the marine air. Findings from the evaluation of revealed that:
The use of epoxy coated pre-stressing strand for beams in aggressive chloride-rich environments is recommended as a "permitted alternative". Back to Top
- The coated strand was abrasion resistant and that normal handling during fabrication did not damage the coating,
- The strands that were monitored did not display significant creep,
- Camber measurements appear normal, showing good bonding, and
- No cracking of the web or bottom flange was observed.
Least-Cost Transportation Planning in ODOT
Least-Cost Planning or Integrated Resource Planning is used in the electric utility industry to broaden the scope of choices to meet service requirements. This typically includes methods to reduce the demands for electricity as well the more traditional electric generation options. Techniques have been developed to compare the cost of electricity generation with the cost of meeting service requirements by reducing electrical usage. In addition to cost considerations, utilities typically take account of uncertainty associated with forecasts and a variety of other considerations in specifying their least-cost plan.
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The basic economic rationale, that users pay a price less than the cost of providing additional service, is the same between the utilities and transportation. However, there are also fundamental differences. Consumers are more concerned about the nature of the service for transportation, the use of the transportation system is affected by the quality of service provided, transportation modes have system or network relations that make it harder to treat sections in isolation, and transportation funding levels determine the amount of service to be provided. Hence, although least-cost principles hold promise to improve transportation planning, the techniques used in the utility industry can not be directly transferred to transportation.
Evaluation of Ice Alert
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One of the goals of road and highway agencies has been to reliably warn motorists of hazardous conditions, particularly the presence of ice on the road. ODOT set out to evaluate a product called Ice Alert® designed for that purpose.
The product was principally tested to determine its degree of reflectivity and sensitivity to temperature changes. The product was evaluated through laboratory and field tests to develop cost data, document maintenance problems, evaluate sitting criteria and determine driver reactions to the device.
AC and CRC
Evaluation of Adjacent AC and CRC Pavement Lanes
On some of Oregon's highways, particularly on the interstate freeways in Eastern Oregon, most of the heavy trucks travel in the outside lane (right lane). With this kind of truck traffic pattern, the right lane experiences significantly higher axle loadings than the left lane, and consequently, the right lane deteriorates much faster than the left lane. After years of service, the left lane pavement is still in good condition while the right lane pavement shows severe surface distress and has to undergo some major rehabilitation in order for the pavement to provide satisfactory service. Maintenance activities, which add additional costs, are often necessary before the major rehabilitation.
In 1989, to resolve this type of pavement problem, the Federal Highway Administration (FHWA) and Oregon Department of Transportation (ODOT) jointly developed an experimental features project constructing a pavement with Asphalt Concrete (AC) material in the left travel lane and Continuously Reinforced Concrete (CRC) material in the right travel lane (AC\CRC adjacent lane), on a section of Interstate 84 (1-84) in eastern Oregon. The construction of the pavement was completed in 1989.
This final report of the experimental features project presents a description of the feasibility of the AC\CRC adjacent lane construction and an evaluation of the cost-effectiveness and performance of the AC\CRC adjacent pavement.
"Fiberoptic Variable Message Signs" - Swift Interchange - Delta Park Interchange Section Pacific Highway (Interstate 5)
The SYLVIA® fiber optic variable message signs (VMS) were installed on the Pacific Highway (I-5) as a part of the "Swift Interchange - Delta Park Interchange" project at milepost 298.47 and at milepost 305.66 in January 1991. Initially, during project construction, the signs were used to provide road construction and delay information to the motoring public. Currently, the signs are being utilized to provide event information, and/or road delay conditions as part of the Freeway Management System.
The evaluation of the SYLVIA® fiber optic VMS was conducted by the Oregon Department of Transportation staff as part of an Experimental Features Program research project. The issues of reliability and ease of operation were investigated. These signs have functioned well, overall. Legibility of the signs is excellent in the conditions evaluated, the maintenance requirements have been minor, and the cost of operation has been reasonable.
"Fiberoptic Variable Message Signs" - Ladd Canyon - Drinking Fountain Grade Section Old Oregon Trail Highway (Interstate 84)
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The SYLVIA® fiber optic variable message signs (VMS) were installed on the Old Oregon Trail Highway (1-84) at milepost 263.4 near La Grande and at milepost 286.7 near North Powder. The purpose of the signs is to warn motorists of fog, winter blizzard conditions and high wind conditions.
The evaluation of the SYLVIA® fiber optic VMS was conducted by the Oregon Department of Transportation staff as part of an Experimental Features Program research project. The issues of reliability and ease of operation were investigated. These signs have functioned well, overall. Legibility of the signs is excellent in the conditions evaluated, the maintenance requirements have been minor, the cost of operation has been reasonable, and driver compliance has been excellent. An additional benefit is that the length of time required to close the highway is significantly lower, since the signs aid maintenance personnel with informing drivers of the closure.
Latex and Microsilica Modified Concrete Bridge Deck Overlays
Latex and Microsilica Modified Concrete Bridge Deck Overlays in Oregon
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This interim report presents information collected from 24 bridge deck overlays constructed in Oregon between 1989 and 1993. Decks were placed on a variety of existing structures using hydro-blasting, milling and diamond grinding surface preparation. All decks were latex or micro-silica modified concrete.
Some decks experienced premature cracking and/or de-lamination. The objective of this study is to determine the possible cause(s) of these distresses and recommended procedures to correct the problem.
Statistical analyses of available environmental and construction information failed to clearly establish the causes of early cracking or de-lamination. Petro-graphic studies did show more micro-cracking was present in the substrate when milling was used compared to hydro-demolition.
Evaluation of the Performance of the Reference Electrodes Embedded in Reinforced Concrete
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This study evaluates the suitability of graphite electrodes for imbedded reference cells in reinforced steel bridges which are cathodically protected with a sprayed zinc anode. It was assumed that a 100 (or 150) mV polarization decay criteria would be used. The work plan was divided into two parts: laboratory scale experimentation and computer simulation.
The response of graphite probes to a varying electric potential was compared to that of an Orion silver-silver chloride electrode. Additionally, commercial and laboratory fabricated electrodes were compared and the effect of electrode conditioning was assessed. The graphite electrodes appear to be a suitable choice for a rugged monitor of the 100mV polarization decay when the cathodic protection system is deactivated, especially when a 3 electrode configuration is used.
A finite difference code was developed to solve for the potential and current distributions in a simplified rectangular geometry. The model addressed cathodic protection of reinforced concrete using a sprayed zinc anode. Input parameters were based on available experimental data. A sensitivity analysis of the input parameters was performed. The effects of pore saturation, concrete cover and applied potential were studied. Oxygen transport significantly contributes to the polarization decay of the reinforcing steel. Additionally, the environmental conditions at the structure greatly affect the potential distribution and the polarization decay.
Pavement Markings Using Waterborne Paint and Visibeads in Region 2
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Oregon Department of Transportation staff evaluated waterborne, latex traffic paint and Visibeads® to determine if the application characteristics and durability of these pavement marking materials deserved future consideration. findings indicated that: waterborne latex paint is an acceptable alternative to conventional paints, at least in geographical areas that have a significant amount of time that the road is dry and pavement and air temperatures are above 50° F; Visibeads® application technology and bead use rate resulted in the recommendation that use of these beads should not be considered until these problems are overcome; and significant improvement in worker safety is also expected.
Evaluation of Porous Pavements for Road Surfaces Volume I
Porous pavements or open-graded asphalt mixtures have been in use in Oregon since the late 1960s. The use of this pavement type has increased over the years because the pores in the mat provide an efficient way for water to drain from the pavement surface. this greatly increases safety in the areas of skid resistance and splash and spray. An added benefit from these pavements is that tire noise is partially absorbed into the voids of the pavement.
The purpose of this study was to evaluate porous pavements, especially the F-mix, as they are used in Oregon. The input from inside (i.e., contractors, ODOT personnel, asphalt experts) and outside (i.e., literature published over the years from agencies in the U.S. and abroad) Oregon was used to study open-graded mixes. This information was then used for improving porous pavements in Oregon.
Laboratory and field studies were performed on Oregon's open-graded mixtures. This tests were designed to understand how the mixture types performed with Oregon's conditions. These test included texture depth, permeability, accident analysis, skid testing, rutting, splash and spray, noise, core gradation, asphalt properties, and tack coat shear testing.
A number of findings resulted from this study. Porous pavements provide a 1-2 dB A-weighted roadside noise improvement when compared to B-mix pavements. This difference would not be perceptible to an individual with average hearing. However, noticeable improvements for the F-mix did occur in the 500-4000 Hz range. Splash and spray visibility is improved, and safety on the roadway is improved. Potential problems with porous pavements include post-construction skid resistance, construction difficulties, and clogging of the pavement mat. Suggestions have been made in this study in terms of solving these problems and increasing the benefits.
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Cold Recycle Pavement Using Urea Urethane Dispersion Agent and Rubber
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This research study was a joint venture of the Oregon Department of Transportation (ODOT), Evans, Loosley, Inc., and Roseburg Paving Company, to evaluate the use of Urea Urethane Dispersion (UUD) agent, with finely ground tire rubber, high float emulsion, and recycled asphalt pavement (RAP). A conventional mix design procedure was not acceptable for the control and test mixes due to the variables associated with the fine, dense RAP gradation, and the compatibility of the high float emulsion with the UUD and rubber. The mixture blend that was used for a control section included: RAP with 2% HFE-150 plus 0.5% added mixing water. The test section included RAP with 1.5% HFE-150 plus 0.5 UUD, 1.8% fine ground tire rubber plus 1% added water.
Approximately 280 tons of control mix and 280 tons of test mix were placed as an overlay. Several hours after being layed, the mixtures could not be compacted without hairline cracking. The mixtures were blanket rolled, dusted with #10-0 material and opened to traffic. After two days under traffic, it was determined that the control section was only partially successful and the test section had not set up. Shortly thereafter, the entire pavement overlay was removed.
The Nature of Rockfall as the Basis for a New Fallout Area Design Criteria for 0.25:1 Slopes
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The data gathered from rolling nearly 2800 rocks off several 0.25H:1V slopes into three differently shaped ditches (flat, 6H:1V and 4H:1V) was used to develop 12 design charts for rock fallout areas. The data was analyzed using simple statistical and graphical methods. The charts can be used to size fallout areas that satisfy specific rock catching requirements. Based on slope height and the shape of the ditch, the charts identify the required fallout area widths that will restrict set percentages of rockfall ranging from 10% to 100% in 10% increments along with 95% and 98%. This report documents the test methods, the means of analysis, the research results, and sample application of the results. The data results in both tabular are graphical form are included in the appendices.
Exploratory Study of Hot-In-Place Recycling of Asphalt Pavements Volume II Appendices
Hot-in-place recycling (HIR) is a method for rehabilitation of asphalt pavements. Potential for cost savings and resource preservation are high because existing pavement materials are processed on-site, with only the addition of small amounts of recycling agent.
The Oregon Department of Transportation (ODOT) constructed HIR projects in 1992 and 1993. In September 1992, ODOT contracted with Oregon State University (OSU) to evaluate the HIR projects, synthesize existing information on HIR, and develop guidelines for HIR use. This report summarizes the information developed during the study:
This report is in two volumes. Volume I includes the body of the report, Volume II includes the appendices. Back to Top
- Construction equipment used on ODOT HIR projects is discussed.
- Field data tom six HIR projects are presented.
- Results of a limited laboratory investigation of HIR are presented.
- Proper project selection was found to be extremely critical to HIR success. A selection procedure is presented.
- Based on information from the field studies and a limited laboratory testing program, a recommended mix design procedure is presented.
Determination of Proper Mixing and Compacting Temperatures of Laboratory Fabricated Asphalt Concrete
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The ODOT Materials Unit has historically used one temperature for the mixing and compacting of laboratory fabricated asphalt concrete specimens. Since switching to the performance based asphalt (PBA) specifications in 1991, the Bituminous Design Crew has continued to use the same specimen preparation technique. However, the method of recommending mixing and lay-down temperatures for construction relies on a viscosity based system. The objectives of this study are to evaluate the differences in physical properties between specimens prepared using the constant temperature technique and a viscosity based temperature selection technique. The physical properties analyzed are: air void content, Hveem stability, Index of Retained Modulus and Index of Retained Strength. Because of the small sample size and the small differences in the mixing and compacting temperatures used in this study, no difference in physical properties could be identified for the two temperature selection methods. It is recommended that the Materials Unit adopt the viscosity based temperature selection method in anticipation of switching to the SHRP PG asphalt grading system and the SHRP gyratory method of compaction.
Low-Cost Piezoelectric Weigh-In-Motion Systems in Oregon: 1988-1993
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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.
Microsilica Modified Concrete for Bridge Deck Overlays - Second Year
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This report summarizes the performance of microsilica concrete (MC) overlays on seven distressed Portland cement concrete bridge decks at three sites in Oregon. This report emphasizes the overlays' condition after two, or in some cases, three years of use.
After two or three years, there was cracking on all seven overlays and delamination on five overlays. On the two overlays without delaminations, the cracking had not increased during the second year of use. On the five overlays with delaminations, the number and length of the cracks and the number and size of the delaminations increased during the second and/or third year of use.
Despite the cracking, all of the overlays had no excessive surface wear or rutting, spalling around the crack edges, potholes, or pop-outs. No maintenance was required during the second, and in some cases the third year of overlay life except on one overlay where methacrylate and sand were used at a cost of $4,000. All of the overlays had adequate tire-to-pavement friction numbers.
The overlays met two of their three design objectives after two or three years of use. They were still adding strength to the deck and providing a smooth and durable wearing surface. However, as they were cracked, it is surmised that they were no longer sealing the underlying deck from the intrusion of chlorides.
The Oregon Department of Transportation (ODOT) is continuing to specify MC as an overlay material. Experience with the material and revision of the MC specifications has reduced construction problems, and consequently, improved the quality of the overlays.
It is recommended that the causes of the cracking on these overlays be investigated.