Extensive design considerations are relevant to reinforcing steel, including bending, cutting, tying, welding, and handling. While this article does not go into detail regarding design concerns of reinforcing steel, specifiers must be aware of these considerations before making their final decisions. Durability, cost, and performance are important factors in the life of reinforcing steel, and each type of bar and coating can provide advantages in each of these areas.
Constructing projects to last 75 to 100 years saves taxpayer money while also creating a stronger infrastructure for the future. Conducting research to determine performance, application conditions, and cost, as well as communicating with those involved in the project, will ensure the correct type of reinforcing steel is chosen to provide the longest possible project lifespan, increasing safety and sustainability for the whole community.
|ATHENS BRIDGE DECK|
Built in 1973, the Athens Bridge in Pennsylvania is an 11-span, four-lane divided bridge utilizing hot-dip galvanized reinforcing bars. Its bridge deck was initially inspected eight years after installation, when concrete cores were drilled and an analysis of chloride contamination and coating thickness was conducted. The chloride levels found in the cores exhibited concentrations between 0.8 and 3.5 kg per 0.7 m3 (1.8 and 7.9 lb per 1 cy) of concrete. The high end of these concentrations was well above the threshold for active corrosion to occur on bare steel.
Despite these extremely corrosive conditions, the coating thickness measurements indicated galvanized coatings approximately three times as thick as required on newly galvanized rebar according to ASTM A767, Standard Specification for Zinc-coated (Galvanized) Steel Bars for Concrete Reinforcement. The Athens Bridge was later inspected in 1991 and 2001, and the analysis generated similar results, with no sign of active corrosion found on the galvanized reinforcement. These inspections indicate the bridge will stand with at least 75 years of maintenance-free corrosion protection.
The Egg at the Empire Center Plaza in Albany, New York, was completed in 1978. This performing arts center was a massive undertaking of architecture, combining aesthetics and function and featuring a concrete and steel stem extending six stories into the ground.
The Egg keeps its shape by wearing a girdle composed of heavily reinforced concrete beams, which use hot-dip galvanized rebar. The superior durability and corrosion protection of hot-dip galvanized steel made it the logical choice for the reinforcement of concrete in such an integral aspect of the structure’s design. The reinforced girdle helps the Egg keep its shape, and directs the weight of the structure onto the supporting pedestal and stem. Thanks to hot-dip galvanized reinforcing steel, the Egg’s extravagant design has not only wowed citizens and visitors for decades, but will remain a beautiful centerpiece of Albany for generations to come.
Laura Hanson is the digital marketing manager for the American Galvanizers Association (AGA), where she has worked for more than six years. She leads the Rebar Focus Group for AGA members while managing all AGA digital marketing initiatives. Hanson holds degrees in design from the University of Nebraska Lincoln and in communications from the University of Denver. She can be reached via e-mail at email@example.com.