U.S. Department of Transportation
Federal Highway Administration
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Federal Highway Administration Research and Technology
Coordinating, Developing, and Delivering Highway Transportation Innovations
This magazine is an archived publication and may contain dated technical, contact, and link information.
|Publication Number: FHWA-HRT-05-003 Date: January/February 2005|
Publication Number: FHWA-HRT-05-003
Issue No: Vol. 66 No. 4
Date: January/February 2005
Below are brief descriptions of products recently published online by the Federal Highway Administration's (FHWA) Office of Research, Development, and Technology. Some of the publications also may be available from the National Technical Information Service (NTIS). In some cases, limited copies are available from the Research and Technology (R&T) Product Distribution Center.
When ordering from NTIS, include the NTIS publication number (PB number) and the publication title. You also may visit the NTIS Web site at www.ntis.gov to order publications online. Call NTIS for current prices. For customers outside the United States, Canada, and Mexico, the cost is usually double the listed price. Address requests to:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Toll-free number: 800–553–NTIS (6847)
Address requests for items available from the R&T Product Distribution Center to:
R&T Product Distribution Center, HRTS-03
Federal Highway Administration
9701 Philadelphia Court, Unit Q
Lanham, MD 20706
For more information on research and technology publications from FHWA, visit the Turner-Fairbank Highway Research Center's (TFHRC) Web site at www.fhwa.dot.gov/research/tfhrc/, FHWA's Web site at www.fhwa.dot.gov, the National Transportation Library's Web site at http://ntl.bts.gov, or the OneDOT information network at http://dotlibrary.dot.gov.
This publication is the result of an extensive literature review of the corrosion process and high-performance reinforcement options for concrete bridge applications. The review is divided into five areas of analysis, comprising (1) the corrosion-induced deterioration process, (2) corrosion-control alternatives, (3) utility of corrosion (pitting)-resistant alloys for applications in environments containing chloride, (4) the pitting mechanism, and (5) performance of various metallic reinforcement types in aqueous solutions, cementitious embedments, test yard exposures, and actual structures. In addition, the review focuses on the properties and uses of several specific alloys, including black steel, MMFX-II (a microcomposite steel), and various grades of ferritic (containing ferric oxide compounds), austenitic (containing carbon and other solutes in solid solution with iron), and duplex (ferrite plus austenite) types of stainless steels. Both solid and clad bars in as-received and pickled conditions are being evaluated.
The review determines that from a corrosion-resistance standpoint the high-performance alloys outperform black steel. Unlike black steel, however, a relatively wide range of corrosion performance—depending upon the alloy and surface conditions—is apparent for their high-performance steel alloys. The typical approach is to identify the reinforcement option that will achieve the target design life at the least life-cycle cost. This approach, however, requires that engineers should know the long-term performance characteristics of each reinforcement option with respect to the anticipated design life (as long as 75–100 years). Since knowledge of the service history for reinforcement options is limited, the necessary data may be obtained through accelerated, short-term tests, in addition to longer term data in salt-contaminated reinforced concrete slabs.
To view the report, visit www.fhwa.dot.gov/publications/research/infrastructure/structures/04093/index.cfm.
This report describes the long-term, natural weathering of 31 post-Southern Exposure (SE) steel test slabs that were not autopsied during FHWA's original exposure testing research conducted between 1993 and 1998. The remaining samples were exposed from September 1998 to December 2002 at an outdoor test yard in Northbrook, IL.
Between 1993 and 1998, researchers tested more than 52 bar materials, leading to the selection of 12 bar types for use in the long-term durability tests described in this report. The tests used concrete exposed to an aggressive SE test that alternated wetting (with 15 weight-percent sodium chloride solution) and drying cycles for 96 weeks. During the test, researchers collected samples of macrocell current corrosion occurring between top and bottom mats, as well as data on the potential for short circuiting. Later, the researchers performed autopsies and subsequent laboratory analyses on the test slabs.
According to the report, the results confirmed that black steel bars produced the highest mean macrocell current density—indicating the least resistance to corrosion—among the bar types, regardless of slab configuration. In contrast, stainless steel bars exhibited negligible mean macrocell current density. Compared with the black bar, the epoxy-coated reinforcing bars (ECRs) used in just the top mat reduced corrosion susceptibility by at least 50 percent, even when they contained coating damage and were connected to the black bar on the bottom mat. Overall, bent ECRs in the top mat, coupled with black bars in the bottom mat, performed the worst among all ECR cases. Straight top-mat ECRs, however, showed a macrocell current density varying from just 7 to 40 percent of the highest black bar case, depending on the size of initial coating damage and the type of bar in the bottom mat. In cases where straight ECRs in the top mat were connected to ECRs in the bottom mat, the mean macrocell current density was no greater than 2 percent of the worst black bar case—even when rebar coatings had defects—and approached the corrosion resistance levels of stainless steel reinforcement. Researchers attributed the improved corrosion resistance in this scenario to (1) reduction in cathodic area, (2) higher electrical resistance, and (3) reduced cathodic reaction.
In cases where the researchers autopsied an ECR slab with negligible macrocell current density, the appearance of the extracted ECR and concrete-bar interface was excellent, with no sign of corrosion. ECR specimens with high macrocell current densities, however, revealed coating deterioration caused by corrosion and exhibited numerous hairline cracks and blisters, along with reduced adhesion, coating disbondment (permanent adhesion loss), and underlying steel corrosion. Researchers found no consistent relationship between the level of macrocell current density and the extent of coating adhesion loss. These results and earlier FHWA studies indicate that adhesion appears to be a poor indicator of long-term performance of coated bars in chloride-contaminated concrete, as no direct relationship exists between loss of adhesion and the effectiveness of ECR to mitigate corrosion.
To view the report, visit www.fhwa.dot.gov/publications/research/infrastructure/structures/04090/.
A failed hanger pin initiated the tragic collapse of one span of the Mianus River Bridge in Greenwich, CT, on June 28, 1983, resulting in the deaths of three motorists. Following the collapse, there was an immediate increase of interest in inspecting and evaluating the condition of bridge hanger pins. Ultrasonic inspection has since become the primary method of performing detailed inspections of inservice hanger pins.
This document describes the fundamentals of ultrasonic testing and general requirements that State transportation agencies and others can use to perform inspections of hanger pins. In addition, the report reviews the inspection of five hanger pins with known defects to emphasize and explain important aspects of the process more completely.
The report describes the techniques that the researchers used in their review, including the pulse-echo technique, pitch-catch technique, decibel scale, piezoelectric effect (electric polarity due to pressure), beam diffraction, beam absorption, beam spread (or divergence), beam centerline location, and distance amplitude correction. Topics included in the section on general inspection requirements are cleaning and coupling requirements, interpretation of signals, defect sizing techniques, effect of wear grooves, phenomena of acoustic coupling, inspection documentation, data collection, and inspector qualifications and certifications.
Results from the experimental program include beam diffraction graphs, distance amplitude correction curves, sensitivity analysis of straight and angled beams, defect sizing analysis, and verification of the acoustic coupling phenomena.
The new Communications Reference Guide (CRG) created by FHWA's Office of Research, Development, and Technology (RD&T) provides users with tools, techniques, and timelines for planning, scheduling, and producing communications products, which include print materials, electronic information and technology, outreach materials, and events. It also links users with communications and marketing resources in the Office of Research and Technology Services (HRTS). This document replaces all previous versions of the Quick Reference Guide.
The CRG will be especially useful to FHWA Contracting Officer's Technical Representatives (COTRs) and their contractors and support staff who develop research and technology communication products according to the FHWA standards and regulations referenced in this publication. The document is available on the Turner-Fairbank Highway Research Center's Web site and is offered as a complement to the FHWA Publications and Printing Handbook. Although the guide is available in printed form upon request, the most recent and up-to-date version is posted on the Web.
To view the guide, visit www.fhwa.dot.gov/publications/research/general/03074/index.cfm