The effects of time and environmental conditions take their toll on virtually everything in our world. In the world of metal and concrete structures, the toll comes in the form of corrosion. Man has fought a battle with corrosion since the earliest days of recorded history.
Various methods and tactics have been tried to slow down the effects of corrosion with some measure of success. Studies performed by John Redner, of the Los Angeles County Sanitation District, over the last 20 years clearly show high build epoxies to be a suitable repair material when handled by trained professionals and installed at appropriate thickensses in a severe corrosive environments.
This paper describes a novel method of repairing steel and concrete vessels with a plural sprayed fiber-reinforced rapid setting structural epoxy system that minimizes costs and down time.
This information taken from an article published in the Journal of Protective Coatings & Linings, November 1991, Volume 8, Number 11, page 48, entitled Evaluating Protective Coatings for Concrete Exposed to Sulfide Generation in Wastewater Treatment Facilities, written by John A. Redner, Edward J. Esfandi, and Randolph P. His.
As professionals studying corrosion remediation, we strive to find an economical solution to slow down the effects of time and extend the life of our aging infrastructure.
This presentation will focus on structural thermo-set epoxy. Epoxy resin has long been used in various forms of protective coatings but had to be diluted with various other resins and solvents to make the finished product more user friendly. Unfortunately, these additives often drastically reduce the physical strength of the neat epoxy resin to 10 ?15% of its original value.
In the early 90s, plural component spray equipment was perfected to accurately meter mix the epoxy resins in their undiluted condition. The finished product was quite remarkable with physical properties in some cases mimicking those of aluminum or mild steel and exceeding the physical properties of concrete 10 to 15 fold.
Extensive research at the University of South Carolina by Dr. Kent Harries1 showed the new spray applied fiber-reinforced epoxy polymer to be a viable method for restoring the integrity of badly deteriorated concrete and metal structures.
In pitted and corroded tanks and holding vessels constructed of mild steel, in some cases with bore holes completely through the vessel wall, the structural epoxy was suitable as a rapid repair material. The structural epoxy would fill the pitted and badly corroded areas and restore both the structural value and the appearance of the vessel. (2)
By allowing the host vessel to serve as a mold for the structural epoxy, one ends up with the best-case scenario possible for a restoration for both metal and concrete. Lab test show the structural epoxy has a yield strength of 10,000psi at ¼ in lay-up. This is the same as ¼ of aluminum. It makes the spray applied structural epoxy the perfect repair material on projects that require quick turn around and restoration of structural value.
1Two research summaries, conducted by the University of South Carolina, entitled Sprayed Fiber Reinforced Polymer (SFRP)
Materials for Concrete Rehabilitation are appended to this paper.
(2)The yield stress of mild steel is 21,000psi, yield stress of aluminum is 10,000psi at ¼, and the yield stress of structural epoxy is 10,000psi.
The chart below summarizes the structural value added by applying structural epoxy to 120 concrete beams in test groups of 10 beams each. The structural epoxy was applied with and without chopp