This packet provides information about how and why to use reclaimed metals in various applications. July Material Summary #1 Performance of Weathering Steel in Highway Bridges Material Summary #2 High-Performance Steel Reclaimed TxDOT Experience Summary of TxDOT experience using reclaimed metals in various applications Metals If you have questions or comments regarding this packet, contact: Rebecca Davio, TxDOT’s recycling coordinator (512) 416-2086 or [email protected] Almost all metals include some recycled Material Brief content. Steel and aluminum are used routinely in the road construction One of the keys to controlling the amount of industry, and they are both infinitely material thrown into landfills is to reuse reusable and recyclable. products as many times as possible. Reuse For example, aluminum sign blanks can conserves natural resources because fewer be used over and over again at less cost new products have to be manufactured. In than buying new blanks. Hydrostripping fact, reusing a material is often more resource- is a process that allows the reuse of ful than recycling it. Reuse eliminates exorbitant waste disposal Americans throw away enough fees and allows consumers to obtain raw aluminum every three months materials at a fraction of their original cost. to rebuild our entire commer- Furthermore, reuse reduces the quantity of cial air fleet. materials dumped in landfills while lessening damage to the environment. 1 aluminum signs that is much more effec- jumped by 27 percent. The Federal High- tive than sanding. Overview way Administration (FHWA) estimates nearly one-third of America’s 578,000 The process involves a high-pressure Steel bridges need to be repaired or replaced. cleaning system that uses 36,000 psi to strip the most stubborn laminates but The steel industry recycles millions of does not harm expensive corrosion tons of steel scrap from recycled cans, The more than 12 million cars resistant coatings. Even the excess water automobiles, appliances, construction recycled in 1995 would cause is filtered and recycled for additional use materials and other steel products. All of a traffic jam stretching from while allowing for safe, nonhazardous this scrap is remelted to produce new New York City to Los Angeles disposal. steel. In fact, the industry’s overall recy- 15 times. cling rate is nearly 68 percent. There are two processes for making steel. There are structural and economic advan- The Basic Oxygen Furnace process, which tages to using steel in bridges. As steel is is used to produce the steel needed for recycled, it maintains its strength and packaging, car bodies, appliances and integrity, so it can be made into one steel framing, uses about 28 percent quality product after another. Its strength recycled steel. makes it highly resistant to extreme natural disasters, such as earthquakes. The Electric Arc Furnace process uses Other engineering benefits include its virtually 100 percent recycled steel to lighter weight, which means lighter produce plate, rebar, structural beams, foundations and lower erection costs. railroad ties and bridge spans. In fact, recycling one ton of steel saves 2,500 Various types of steel can be made to pounds of iron ore, 1,400 pounds of coal satisfy different end-use requirements. For and 120 pounds of limestone. example, weathering steel, which does not require painting, is low maintenance. Under the Transportation Equity Act for High performance steel has enhanced the 21st Century (TEA-21), public fund- durability, weldability and strength. ing for bridge repair and construction 2 Aluminum Like steel, aluminum is a recycled metal used routinely in road construction. It is the most abundant metal on earth, but it still makes sense to recycle it. Doing so saves 95 percent of the energy necessary to produce aluminum from virgin ore. The 1.7 million tons of steel recycled in 1997 would yield enough steel to build 200 Eiffel Towers. The all-aluminum can was introduced in 1964. Today aluminum cans are the most common material recycled by consumers. More than 51 percent of a new aluminum can is made from recycled aluminum. In fact, aluminum beverage cans return to the grocery store shelf after recycling, remelting, rolling, manufacturing and distribution in only 90 days. Every minute of everyday, an average of 113,204 aluminum cans is recycled. Approximately 32 cans make one pound of aluminum. 3 appearance, texture and maturity of this estimated cost of collection and disposal Material Summary #1 oxide coating all depend on three natural of materials from a structure repainting factors: time, degree of exposure and project were so great that the structure Performance of Weathering Steel in atmospheric environment. was either abandoned or replaced with a Highway Bridges new bridge. Over time the oxide coating changes from Since 1964, bridge engineers have utilized a “rusty” red-orange to a dark, rich, Inappropriate Applications uncoated weathering steel because of purple-brown patina. The moderately While weathering steel is performing well performance, economical and environ- rough texture becomes more distinct as overall, there are some circumstances mental benefits. As a result, more than the coating thickens. This weathering where weathering steel is not recom- 2,300 bridges in the U.S. have been built process extends up to 20 or 30 years mended in a bare, uncoated condition, with this material over the last 30 years. depending on these natural factors. because the protective, tight oxide film Approximately 90 percent of TxDOT Benefits will not form properly. steel bridge projects use weathering steel. Weathering steel’s cost-effectiveness as a Weathering steel is not recommended in Studies show that using weathering steel construction material has been demon- • Atmospheres containing concentrated reduces both initial and life cycle costs. strated in both short- and long-term corrosive industrial or chemical fumes. Current U.S. highway legislation man- savings. The additional cost of this grade • Locations subject to saltwater spray or dates life cycle cost analysis in the high- of steel is offset because the need for salt-laden fog. way materials selection process. initial and maintenance painting of the • Applications where the steel may be The enhanced atmospheric corrosion structure is eliminated. continuously submerged in water, resistance of steel is indicated by the letter buried in soil, or on bridges where Environmental benefits also result from “W” that follows the grade. water runoff contaminated with deicing the use of this material. The absence of salts drains through leaky seals, open The Weathering Process initial painting reduces volatile organic joints or expansion dams. compounds (VOC) emissions when oil- • Applications where the steel is in direct During the weathering process, steel based coatings are used. In addition, the contact with timber decking. Timber develops a durable, tightly adherent need for coating removal and for contami- retains moisture and may be treated protective oxide coating. Alloy content nated blast cleaning debris disposal over with salt-bearing preservatives. and environmental conditions influence the life-span of the structure is eliminated. the formation of this film on steel. The There are documented cases where the 4 • Bridges over tunnel-like highways that References permit salt-laden road sprays caused by traffic passing under the bridge to 1. Steelworks. Performance of Weathering Steel in Highway Bridges: A Third Phase accumulate on the superstructure. Report,http://www.steel.org/markets/infrastructure/bridges/phaseIII.htm Problems associated with these circum- 2. Bethlehem Steel. Weathering Steel: The Weathering Process, http://www.bethsteel.com/ stances can be avoided by eliminating divisions/burns/bhwsweath.htm joints and by using good details. 3. Federal Highway Administration. Uncoated Weathering Steel in Structures. FHWA Conclusions Technical Advisory T 5140.22, October 3, 1984. There is a long history of uncoated weath- 4. Federal Highway Administration. Forum on Weathering Steel for Highway Structures: ering steel bridges performing well Summary Report, FHWA Report TS-89-016, June 1989. throughout the U.S. For help in evaluating areas suitable for use of weathering steel, contact: Ronnie Medlock, TxDOT’s Steel Bridge Fabrication Director, CSTM, (512) 467-3781. 5 Material Summary #2 Superior Performance in bridge structures while remaining cost- effective. The new steel alloys possess superior High Performance Steel weldability and toughness compared to Testing and Evaluation conventional steels of this strength range. High Performance Steel (HPS) is defined The lower welding preheat requirements An extensive effort is underway to evalu- as steel that has enhanced durability, are due to lower carbon and carbon ate the weldability and structural perfor- weldability, strength and toughness equivalents. Lower sulfur content allows mance of bridge members fabricated from characteristics due to a refined metallurgi- significantly increased toughness. This HPS-485W. Standard tension and CVN cal formulation. extra toughness provides a high resistance tests are performed on each plate made to brittle fracture that allows structures to available through this program. This In the past, steels with enhanced strength tolerate high fatigue levels without risk of process will be continued as future plates have experienced a higher percentage of sudden failure. This provides added are produced to develop