By Teresa Hansen, Associate Editor
Power plant owners spend millions of dollars each year on structure maintenance, particularly on concrete repairs. While concrete remains the choice building material for power plant structures, it is not without its problems. Concrete is prone to cracking and spalling as oxygen and water vapor in the atmosphere react with the embedded steel in reinforced concrete. As contaminants seep in, the reinforced steel bars corrode, threatening the long-term stability of structures.
Traditional concrete repair methods have ranged from simple patching on an annual – and recurring – basis to total knockdown and rebuilding, with costs running into millions of dollars per structure. Innovative Engineering Technologies (IET), a Stuart, Fla.-based engineering company, has developed a patented new product called PermaTreat that the company believes will revolutionize concrete repair.
PermaTreat’s formulations are composed of mixtures of chemically reactive silicates. When used in conjunction with VAPIS, a unique pressure injection system, PermaTreat induces various permanent chemical and physical changes in the concrete, ultimately arresting corrosion. PermaTreat’s special chemical formulation of reactive silicates penetrates deteriorating concrete, permanently halting reinforcing steel corrosion and improving the strength and ductility of the concrete to levels higher than original construction.
The 20-year-old Zurn cooling towers at Anclote Power Plant are structurally sound, but riddled with concrete spalling and corrosion.
A March 2005 test at the Anclote Power Plant near Tarpon Springs, Fla., demonstrated the product’s potential. A fossil fuel power plant that operates 24 hours a day, Anclote has two 200-foot diameter Zurn cooling towers that also operate 24 hours a day. Each tower has twelve 32-foot diameter fans and 400 horsepower motors. The 20-year-old plant is structurally sound, but is riddled with concrete spalling and corrosion.
St. Petersburg, Fla.-based Progress Energy, the power plant’s owner, agreed to allow IET to test the corrosion rate and to treat a test area with their product at no charge. Gordon Anderson, a consulting engineer who has been associated with the Anclote Power Plant for the past 15 years, said, “Concrete is certainly subject to erosion and corrosion. In past years, the concrete cooling towers at Anclote have been patched and repaired many times using conventional approaches. IET offered a novel repair method.”
“The solution halts the corrosion of steel reinforcement bars inside the building materials. This means that repairs are done only once, not in three to five year cycles to the same deteriorating concrete,” explained Edward E. Young, Jr., IET’s president.
PermaTreat was injected directly into the crack in Vertical Support Column #59, penetrating the entire depth of the two-foot thick structure.
A pretest corrosion analysis of Anclote Cooling Tower No. 2 Vertical Support Column #59 showed cracking and spalling on the surface area of the column. IET used an instrument called the GalvaPulse to test for corrosion inside the two-foot thick column. GalvaPulse is a cutting-edge, rapid nondestructive electrochemical polarization test method that evaluates steel reinforcement corrosion and corrosion rate. FORCE Institute in Broendby, Denmark, developed this method and it has gained wide acceptance in the study of steel in concrete corrosion. After initial testing on a 3 feet by 3 feet pretest grid with 10 inch spacing, IET found that the column had a high corrosion current with a peak measurement of 1,198.61 micrometers per year (µm/yr). The average for the area measured was 328.55 µm/yr., an extremely active corrosion rate that could result in a premature failure.
Using the VAPIS application equipment, IET injected PermaTreat directly into the concrete under 70 to 80 pounds of pressure. The chemicals penetrated the entire depth of the two-foot thick structure, with measurable results within two hours. A GalvaPulse post test revealed a passive measurement of 200.62 µm/yr, with the average for the area measuring 95.39 µm/yr. A visual inspection and review of the test results indicated a dramatic reduction in corrosion current.
“Originally, we were very skeptical of the company’s claims regarding the merits of PermaTreat,” said Wayne Toms, Anclote’s plant maintenance superintendent. “Wow! was our reaction after the test. Perhaps we discovered a panacea for concrete repair.”
According to Young, “PermaTreat increased compressive and tensile strength, while reducing porosity and improving the structure’s resistance to acids. And, the chemical reactions are permanent, reducing future potential repair costs.”
Prior to the PermaTreat solution, Progress Energy had been advised to knock down the cooling towers and replace them with new structures costing $11 million to $15 million. PermaTreat could potentially save Progress Energy, its customers and its shareholders millions of dollars while eliminating structural waste.
Consultant Anderson agrees that there was quite a difference in the measurements taken before and after the PermaTreat application. But, Anderson said, “The real test is the test of time. What will the repaired structure look like in one year, two years, five years and 10 years?”
The test column will be checked again before the end of the year to determine the future course of repair work. “Because it is a permanent repair, PermaTreat has the potential to revolutionize the concrete repair industry by avoiding yearly patchwork that costs building owners thousands, and perhaps millions, of dollars,” said Young. Saving money is the bottom line success indicator in any company.