Materials

Residual Dye (Lubricant) on Galvanized Fasteners – How Much Is Too Much?

The nuts of galvanized fasteners used on bridges are coated with a wax-based lubricant that contains a dye. Once installed, the fasteners are cleaned to remove the wax prior to painting. Cleaning is typically accomplished using a combination of solvents and hand tools, but questions are often raised as to how much residual dye on the surface is acceptable for painting. To gain better insight into this issue, the Florida Department of Transportation (FDOT) commissioned a research project to evaluate the performance of a bridge paint system applied to mechanically galvanized and hot dip galvanized fasteners after removal of various amounts of lubricant. This paper summarizes the research that was undertaken and the results.

Download the FDOT Bolt Lube Study Final Report (.pdf)

Environmental Suitability of Weathering Steel Structures in Florida – Materials Selection, Phase 2

For the purpose of establishing guidelines for selection of weathering steel material for bridges in Florida, data were collected to help establish appropriate guidelines. There were 30 monitoring stations set up for direct (weight loss) measurements and weather data. Data indicated that the corrosion rates in Florida are generally low for weathering steel. The use of weathering steel material for bridges in Florida in the context of adjusted guidelines is very favorable. Consideration should be given to increasing the allowable deposition rate of chloride to approximately 13 mg·m–2·d–1 corresponding to 4 miles from the shoreline. An alternative direct assessment at the site considered is recommended for determining the advisability for uncoated weathering steel in this manner: (1) Expose several plate specimens and collect monthly for a minimum of 4 months. (2) Directly compare the time series weight losses to known corrosion studies. ISO methods permit this alternative. Additionally, estimates of chloride and sulfur compound depositions can be obtained from the same exposed panels by analyses of panel wash water prior to oxide removal, if desired. The advantage of direct assessment is that no environmental factor will likely be neglected, such as pH, ammonia, fertilizer, ozone, exposure/sheltering, or unanticipated factors (positive or negative).

Download the Weathering Steel Study Report (.pdf)

Investigation of the Effect of Speed on the Dynamic Impact Factor for Bridges with Different Entrance Conditions

The dynamic interaction of vehicles and bridges results in live loads being induced into bridges that are greater than the vehicle’s static weight. To limit this dynamic effect, the Iowa Department of Transportation (DOT) currently requires that permitted trucks slow to five miles per hour and span the roadway centerline when crossing bridges. However, this practice has other negative consequences such as the potential for crashes, impracticality for bridges with high traffic volumes, and higher fuel consumption. The DOT has conducted a study whose main objective was to provide information and guidance on the allowable speeds for permitted vehicles and loads on bridges.

Download the Study Report (.pdf)

Nondestructive Testing for Concrete Bridge Decks and Tunnel Linings (R06 A/G)

Beneath the surface of many of America’s bridges and tunnels are structural deficiencies that the eye cannot see. Now, new non-destructive testing (NDT) technologies are available to help transportation agencies inspect concrete bridge decks or tunnel linings. Developed through the SHRP2 Program, these methods help to define the actual extent of deterioration—beyond what can be seen—for improved repairs and provide real-time solutions, saving transportation agencies time and money.

Visit the SHRP2 Non-destructive Testing Website

National Use of Fiber Reinforced Polymer (FRP) in Bridges and Structures

For over 30 years, the FHWA has promoted the use of FRP composites for highways and bridges.  In September 2013, an international workshop titled “Aging of FRP Composites” was held at Ashburn, Virginia.  The workshop Proceedings are available for download at:

FRP Workshop Proceedings (.pdf)

The Oregon DOT has also conducted research on the use of FRP composites for shear strengthening and on durability of FRP composite materials. The agency has used FRP composite materials for bridge components, FRP wraps and strips used to strengthen or reinforce concrete.  Oregon’s experience with FRP is available for download at:

Oregon DOT’s Experience with FRP (.pdf)

Chloride Threshold Values for Grout Used in Post-Tensioned Bridges

The U.S. Federal Highway Administration has released a technical brief that explains how two chloride threshold values of 0.4 and 0.8 percent by weight of cement were determined for corrosion initiation and corrosion propagation for grout used in post-tensioned bridges.

Read the Technical Brief