It's a fact of life for building owners and structural engineers everywhere: embedded steel in concrete corrodes. But Innovative Engineering Technologies (IET), a Stuart, Fla.-based engineering company, developed Perma Treat—a patented product that eliminates the need to conduct excessive demolition on reinforced concrete structures to remove rust from embedded reinforcing steel. It also has received accolades from the Space Alliance Technology Outreach Program (SATOP), the private sector outreach program of NASA. Penn State University research verified what SATOP discovered in tests conducted on distressed concrete—an increase of more than 100% of the modulus of elasticity.
Oxygen and water react with embedded steel in reinforced concrete, forming corrosion byproducts that are greater in volume than the original steel. Because of that internal expansion, the concrete breaks. Steel is susceptible because chlorides penetrate the concrete and disable the passivating layer of alkaline concrete.
Used in conjunction with VAPIS, a pressure injection system, PermaTreat's formulations are composed of mixtures of chemically reactive silicates that implement a variety of permanent chemical and physical changes in concrete, ultimately arresting corrosion. The product uses a special formulation of reactive silicates to penetrate deteriorating concrete, permanently halting reinforcing steel corrosion and improving the strength and ductility of the concrete to levels higher than original construction.
The testing facility
The company tested the product at Anclote Power Plant near Tarpon Springs, Fla. Anclote is a fossil fuel power plant that operates 24 hours a day with two 200-foot diameter cooling towers that operate 23 hours a day. Each tower has twelve 32-foot diameter fans and 400 hp motors. The plant is 20 years old and, although structurally sound, has a lot of concrete spalling and corrosion.
Gordon Anderson, a consulting engineer who has been associated with the Anclote Power Plant for the past 15 years, says, “Concrete is certainly subject to erosion and corrosion. In the past years, the concrete cooling towers at Anclote has been patched and repaired many times using conventional approaches. IET offered a novel repair method.”
Putting it to the test
A pretest grid was laid out at 3x3 feet, with 10-inch spacing. After initial testing on one column, which showed cracking and spalling on the surface area, IET found that it had a high corrosion current—which could result in premature failure—with a peak measurement of 1198.61 micrometers/year. The average for the area measured was 328.55 micrometers/year.
PermaTreat was injected directly into the concrete under 70 to 80 pounds of pressure. The chemical penetrated the entire depth of the 2-foot-thick structure, with measurable results within two hours. A post test revealed a measurement of 200.62 micrometers/year, with the average for the area measuring 95.39 micrometers/year—a dramatic reduction in corrosion current.
IET president Edward E. Young, Jr., says, “PermaTreat increased compressive and tensile strength, while reducing porosity and improving the building's resistance to acids. The chemical reactions are permanent, reducing future potential repair costs.”
Although consultant Anderson agrees that there was quite a difference in the measurements taken before and after, and that he was impressed with the product, he says, “The real test is the test of time. What does the repaired structure look like one year later, in two years, five years, and 10 years?” The test column will be checked again in November to determine future repair work.
For more information, contact IET at 800-460-2701 or visit www.ietpower.com.