Commitment to safer bridges
With sadness, we remember the one-year anniversary of the Aug. 1 bridge collapse in Minneapolis. Our thoughts continue to go out to the victims’ families.
We’re encouraged that AASHTO has taken an honest look at the state of our nation’s bridges, with the release of a recent report. We look forward to working with you to make our bridges safer.
John Grissinger, President
In this issue:
FHA: Report on bridges
New epoxy for extreme temps
World's longest covered bridge
How to choose the best grout
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Our sales team offers some of the best technical support in the industry. Find your rep here:
Steve Raleigh, East
Keith Miller, Midwest
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Andy Freeman, Northwest
Marty O’Mara, Upper Midwest
Jerry Byrne, D.O.T. specialist
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Our research and development team is continually working on new ways to support the industry, as well as customizing certain products to meet specific needs.
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FHA: Billions needed for bridge updates
The Federal Highway Administration estimates it will cost $140 billion if all the nation’s 600,000 bridges were repaired or modernized today. Those figures are part of a report issued just last week by the American Association of State and Highway Transportation Officials (AASHTO).
Key findings from the report, “Bridging the Gap: Restoring and Repairing the Nation's Bridges:”
• Age - The average age of the nation’s bridges is 43 years. Most were built to last 50 years. Almost 20 percent of what AASHTO calls "baby boomer" bridges were built more than 50 years ago. As age and traffic increase, so does the need for repair.
• Traffic congestion – Many of the nation's large-scale bridges have become “chokepoints” on the country's freeway system and a drain on the nation's economy. The top 10 highway interchange bottlenecks cause an average of 1.5 million truck hours of delay each year.
• Soaring construction costs – The costs of steel, asphalt, concrete and earthwork have risen by at least 50 percent in the past five years, forcing delays of bridge improvements and replacements. Nearly every state faces funding shortages that prevent them from ongoing preventive maintenance, repair and replacement needed to keep their bridges sound indefinitely.
Click here for a copy of the report. Or, visit this site for a video of the news conference.
Unitex is launching a product for high-strength concrete repair and patching that cures quickly in all weather conditions. It’s a new option for contractors, maintenance supervisors, departments of transportation (DOT) and others.
Pro-Poxy AWP is an epoxy urethane hybrid. Compared with similar products, it is engineered to be less sensitive to moisture during the repair, and is stronger and more flexible afterward.
 Pro-Poxy AWP can be used for patching, spall and crack repairs. The Unitex epoxy urethane hybrid is perfect for surfaces that endure extreme heating and thawing, such as parking structures or airport ramps. It is a good choice, as well, for situations where repairs must be done very quickly, including high traffic areas in warehouses. It also can be used in extremely cold environments — including repairs of freezer floors.
“In two separate applications, we’ve already seen how well Pro-Poxy AWP works for repairs in extreme temperatures,” says John Grissinger, Unitex president. “We believe we have an exceptional solution for extreme temperature scenarios where speed, strength and flexibility are critical.”
Pro-Poxy AWP is available through distributors. For more information, contact us at: 800.821.5846 or email scott@unitex-chemicals.com.
World’s longest covered bridge gets epoxy overlay
The world’s longest covered bridge, the Hartland Covered Bridge in Hartland, New Brunswick, Canada, is now smoother and safer, with an epoxy polymer overlay from Unitex. The wood deck of the 107-year-old, 1,282-foot bridge should now last for decades.
The Unitex Pro-Poxy Type III D.O.T. epoxy polymer overlay is traditionally used on concrete surfaces, but has proven successful on wood bridges as well. The epoxy is also used on parking structures, pedestrian bridges and more.
The Hartland Bridge has been undergoing the most extensive rehabilitation in its long history, which includes the deck repairs.
The first stage of the deck repairs was completed in June. Remaining deck repairs are set for September.
The crews used a unique approach. For the first application, they added extra aggregate into epoxy. This thick mixture kept the epoxy from leaking through the timbers. On later applications, they first spread the epoxy onto the deck and then spread the aggregate by hand into the wet epoxy. This approach, as opposed to blowing the aggregate onto the surface, kept the aggregate away from the St. John River, immediately below.
The epoxy overlay was applied in the morning and allowed to cure overnight. The covered bridge kept the surface area cool, which provided for longer working times. The crew was even able to work on rainy days.
The Unitex epoxy polymer overlay application is lighter, more flexible, and more weather and corrosion-resistant than resurfacing with concrete or asphalt. Compared to using concrete for repairing bridge surfaces, the Unitex epoxy overlay reduces weight added to the structure by more than 50 percent. It also provides better skid-resistance.
To see a brief video on how Unitex Type III D.O.T. was used in another project, go here.
Machine base grouting: choosing the right grout
Base grouting is very important for extremely heavy, critically aligned, or high vibration rotating machines. Base grouting allows the machine’s weight to be evenly distributed to the substrate.
By contrast, a machine placed directly on a concrete surface may sit unevenly. This means the machine will likely move during operation, allowing “point loading,” that can fracture the base substrate. Ultimately, the entire base will fail.
It’s important, however, to choose the right kind of base grout – either cementitious or epoxy grout -- to achieve the best support for the machine.
The grout must flow under the machine, so that it develops a complete contact between the machine and the base. Also, consider flow versus set time, low air content, and adequate strength.
Use cementitious grout if:
• Less than 10,000 psi compressive strength is required.
• Machines to be supported are low vibrating.
• The environment is non-caustic.
• Low cost is a must.
Use epoxy grout if:
• Greater than 10,000 psi compressive strength is required.
• Machines to be supported are high vibrating or have a high energy input.
• The environment is caustic.
• Long-term durability is more important than lower cost.
The following factors should also be considered when choosing between cementitious and epoxy grout:
• Energy Absorption
Epoxy grouts are capable of vibration energy absorption, which helps ensure long foundation life. Cementitious grouts absorb less energy.
• Plastic Shrinkage Cracking
Cementitious grouts are susceptible to plastic shrinkage cracking – the shrinking of concrete that results when water evaporates from the surface of freshly placed concrete faster than it is replaced by bleed water. This can occur because cementitious grouts have very low water content and are highly reactive. Proper curing is also critical.
Epoxy grouts use no water and shrinkage cracking is not an issue.
• Potential for Mixing Error
It is a common mistake to add extra water to cementitious grout, leading to durability issues. Epoxy grout comes in kits and does not use water.
• Cure Time
Epoxy grout can usually be fully loaded within 24 to 48 hours after placement. Cementitious grouts need more time to gain strength.
• Cold Weather Placement
Cold weather placements must be handled carefully with both cementitious and epoxy grouts. Heating the substrate is beneficial to both epoxy and cementitious grouts. Covering newly placed material with a blanket and providing a heat source under the blanket will aid in strength gain for both types of grout.
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