News | Blog    

Cathodic Protection Technology Corrosion Destroys Concrete
“The way I see it, had I been able to convince our Board back in 1996 to go with CPT, we would have prevented $1.9M in restoration repairs, noise disruption, rental loss, and everything else that comes with concrete repair.”

-- Duncan Dowling, President, Blue Surf Condominium

Company Understanding the corrosion proces Technology Services Project Portfolio Contact Us

Latest News

End the restoration cycle

September 17, 2009 - 6:13 AM

Can we stop corrosion? 

The characteristics of new concrete naturally inhibit corrosion activity of reinforcing steel.  However, coastal structures are exposed continuously to salt-laden air.  This exposure eventually saturates the concrete with chlorides and initiates corrosion activity on the reinforcing steel.  The reinforcing steel corrosion reaction turns the steel to rust (iron oxide).  The formation of rust, which takes up significantly more volume than steel, exerts tremendous internal pressure on the concrete leading to cracking and delamination of the surrounding concrete.  Delaminating concrete weakens the structure, creates potential hazardous falling debris and is visually unappealing.  The corrosion rate accelerates exponentially with time and is increased by other factors such as high temperature and humidity.  Once the concrete has become contaminated with chlorides at the reinforcing steel level, no traditional repair methods such as patching, sealer or membranes will stop the corrosion because all the elements of corrosion remain.  One method for stopping corrosion is the complete removal of all the contaminated concrete which in most cases is not practical or feasible.  The only economical, proven, permanent solution for stopping corrosion is the installation of an impressed current cathodic protection system.  It may be a 10-15 year process for the first cycle of chloride contamination and concrete damage to occur but without proper corrosion mitigation techniques additional corrosion will cause new concrete damage in a relatively short time frame typically four to six years after a restoration cycle is completed. Call us today at 1-800-392-0274 to find out how we can help you stop major restoration - Guaranteed!

Hot off the press

September 6, 2009 - 3:51 PM

A Case Study: 2100 Towers STOPS Major Restoration

2100 Towers is no different than any other condominium up and down the coast of Florida. The environment that the condominium is surrounded by is harsh; full of salt laden air, moisture, wave action, water, heat, and humidity. If the condominium's concrete is not maintained on an annual basis, the concrete, exposed to this environment, will begin to have major structural and corrosion issues.

In 1997, 2100 Towers was going through their third major concrete restoration in an 11 year period- and quite frankly they were fed up. This was a very expensive and inconvenient cycle, and 2100 Towers was motivated to stop it. They invested in an impressed current cathodic protection (ICCP) solution and 12 years later, 2100 Towers has been free of major restoration. This year, 2100 Towers was awarded the 2008 International Concrete Repair Institute "Award of Excellence" for longevity. Below is a case study outlining why 2100 Towers went through three major restorations in 11 years, what their options were, and how the investment has paid off.

Why did 2100 Towers go through three major restorations in 11 years?

The answer is very common for condominiums up and down the coast of Florida-corrosion of reinforcing steel. Coastal structures are constantly exposed to salt laden air. This exposure eventually saturates the concrete with chlorides and initiates corrosion activity in the reinforcing steel (Rebar). These corrosion "cells" result in expansive forces caused by corroding rebar, which crack and delaminate the surrounding concrete. Delaminating concrete weakens the structure, creates potentially hazardous falling debris, and is visually unappealing.

The corrosion rate accelerates with time and is increased by other factors such as high temperature and humidity. It may be a 10 to 15 year process (in 2100 Towers' case it was 13 years) for the first cycle of chloride contamination and concrete damage to occur. However, without proper corrosion mitigation, even the best repair methods will not prevent additional corrosion, resulting in new concrete damage in a relatively short period of time-typically four to six years. One of the main reasons for this is that newly repaired concrete poured next to chloride contaminated concrete actually accelerates the corrosion cell. The result is a never ending cycle of concrete repairs, inconvenience, and special assessments. In 1997, this was exactly where 2100 Towers found themselves to be-and they wanted to stop the vicious cycle. 

What were the options for 2100 Towers?

Typically there are three options for homeowners to choose from and they include:

  • Conventional repair with short-term corrosion control solutions, such as waterproof coatings and sealers, galvanic (sacrificial zinc), migratory corrosion inhibitors, corrosion admixtures, and rebar coatings. These solutions fall into the "corrosion control" or "corrosion prevention" category in an attempt to control or slow down corrosion. Although these solutions do not stop corrosion, they typically come with a five year warranty on repaired areas only, and the life expectancy is anywhere from four to six years.
  • Full tear-off. Typically, this solution is cost effective when at least 40 percent of the concrete is deteriorated. It is more economical to replace the entire slab because a full pour unit cost is normally about half the cost of a partial repair unit cost. If this option is chosen, the contractor removes 100 percent of the walkway and/or balcony slabs and re-pours with new concrete. New concrete is high in pH and alkalinity and not chloride contaminated, therefore, it should have a life expectancy of 30-plus years. However, the newly poured concrete does not come with more than a one to five year workmanship warranty and will only live up to its 30+ year life expectancy if it is properly maintained. This means the condominium must be consistent in maintaining the structure with proper coatings and all penetrations like shutters, railings, door sliders, etc., are properly sealed.
  • Conventional repair with long-term impressed current cathodic protection solutions. These solutions have been scientifically proven to "stop" corrosion and are backed by agencies like the Federal Highway Administration, Department of Transportation, and the National Association of Corrosion Engineers. Some of the more experienced solution providers offer a 15 year warranty that warranties all concrete from future cracking and spalling where the system is applied and the life expectancy is anywhere from 15 to 25 years.

Conventional Repair with Short-Term Corrosion Control Solutions

2100 Towers was constructed in 1973, and as early as 1986, they went through their first major restoration. This was only 13 years after initial construction, which is indicative of how the environment plays a substantial role in deteriorating concrete. In this first restoration, 2100 Towers spent $500K using traditional repair methods. Fast forward to 1992, 2100 Towers was in the middle of their second major restoration-just six years later. This time around, 2100 Towers spent just under $1 million to repair roughly 20 percent of their deteriorated concrete. Both the 1986 and 1992 restorations used quality waterproof coatings and sealers thought to be a long-term fix for concrete cracking and spalling. As we discussed above, even the best repair methods will not prevent additional corrosion, resulting in new concrete damage in a relatively short period of time (typically four to six years). Keep in mind, if you're having concrete cracking and spalling issues, your condominium is most likely 10 to 15-plus years old. When 2100 Towers realized that the chloride ions that had been penetrating their concrete for a long time were not going away, they decided to look at alternative solutions. They learned by their prior restoration experiences that short-term repairs will address the symptom but not the root cause of the concrete spalling and cracking. Now, fast forward to 1996, just four years later, 2100 Towers was preparing for their third major restoration cycle. The time between the first and second restoration was six years; however, the cycle between the second and third restoration was four years. This is typical because, as we described above, putting new concrete next to chloride contaminated concrete accelerates the corrosion cell. The result is secondary spalling occurring every four to six years.

Although there were no viable short-term corrosion mitigation solutions in the market back in 1986 and 1992, there are today. These short-term solutions are designed to "control" or "slow" the corrosion process down versus stopping corrosion. Most short-term solutions offer a five year warranty on repaired areas only and not the rest of your concrete surface. There is a significant amount of research available that supports the life of these types of solutions, typically anywhere from zero to six years. As you can imagine, after three major restoration cycles in 11 years, and millions of dollars spent on repairs, 2100 Towers was very motivated to find a long-term solution that would stop the vicious restoration cycle. 2100 Towers considered some of the short-term options, but in the end, chose a solution that offered a long-term life.

Full Tear-Off

Both the 1986 and 1992 restorations were extensive, major concrete repairs, repairing and replacing up to 20 percent of the concrete. This is a significant amount of structural work and the owners were very concerned about the amount of concrete that had to be restored. In fact, during the 1992 restoration cycle, 2100 Towers was informed by both the contractor and engineer that the chloride contamination in the concrete was so severe that full tear-off was inevitable in four to six years. Based on the unique design and architecture of the structure (2100 Towers is a flat-plate system), if 2100 Towers had to undergo full tear-off of balconies, a contractor would have to work inside the units to install shoring in order to support the interior slabs while the exterior slabs were removed-creating a balance effect. Not only would this have been an expensive endeavor (estimated at $8-10 million), it would have shut the condominium down. Those that were full-time residents would have to move out and those that rented out their units would experience significant rental income loss. This was a precarious and expensive endeavor, motivating 2100 Towers to be diligent in their research in finding an alternative solution that would prevent them from having to rip out and replace all of their balconies.

Conventional Repair with Impressed Current Cathodic Protection (ICCP)

As the third major restoration project approached in 1996, the board of directors voted to hire an objective corrosion Engineer and astructural Engineer to survey the condominium and make recommendations for repairs with the objective of eliminating the cycle of deterioration caused by corrosion of reinforcing steel. 2100 Towers learned over the years that the salt/chloride contamination that initiates the reinforcing steel corrosion is in the surrounding concrete (concrete that wasn't repaired), and that rehabilitation methods that "stop" the corrosion must either include the complete removal of the contaminated concrete or an ICCP system. Based on their prior experiences, they knew too well that repair methods such as spall patching, waterproofing, and sealers, would only slow the corrosion in the area repaired and ultimately lead to another costly restoration.

The board of director's objective was a long-term fix, but they did not want to spend $8-10 million, so they elected to implement the ICCP system on the eastern third of the building as a test to see how the solution would perform. This decision was recommended by multiple Engineers and 2100 Towers was comfortable because it was a proven technology, it was  predictable; it was designed to protect all of the concrete; and it came with a long-term, no-corrosion warranty for the entire balcony. The east side of the building was completed in 1997. At the time, there was still a very spirited debate on whether or not 2100 Towers should invest in and install the ICCP solution on the rest of the structure. However, after a reasonably seamless installation in 1997 and a six month inspection report revealing that the system was performing as designed, a unanimous vote was cast to implement the ICCP solution on the remaining two-thirds of the structure.

Ben Mills, structural and threshold engineer of record: "I have been an engineer for over 30 years and when we looked at 2100 Towers, there was massive structural damage to the balconies which were an integral component of the building itself. If the balconies or interior slab failed, the entire structural integrity would be compromised. Our main objective was to remove the contaminated concrete and restore it using proper strength concrete, bringing the balconies back up to strength. In order to avoid having to do the same restoration in four years, we installed an impressed current cathodic protection system. I highly endorse the solution as it is the only solution in the market that has been proven to stop corrosion and break the expensive cycle of repair. In the end, we saved 2100 Towers a significant amount of money-not to mention the heartache of dealing with all that comes with restoration. Now that the system has been running for 12 years, time has proven that impressed current cathodic protection is a cost-effective solution. Considering 2100 Towers went through three restorations in 11 years, I would venture to say that if you asked the owners, they would tell you they are grateful they made the decision to stop the costly restoration cycle."

Was the Decision Cost Effective for 2100 Towers?

When you look at the history of 2100 Towers, had they gone down the path that was predicted in 1992, they would have spent $8-10 million to rip out and replace their balconies. This does not factor in the incremental costs associated with the rip-out and replace process, such as replacing rails, sliding doors and shutters that may be out of code, lost rental income, livable space, etc. When a condominium looks at bottom line options for conventional repair with short-term corrosion mitigation solutions or conventional repair with long-term impressed current cathodic protection, the cost for the long-term option is only up to ten percent more-ultimately saving the homeowners millions and millions of dollars.

Eventually, the ICCP system was installed on the rest of the structure totaling 50,000 sq ft of balconies. The total restoration, including installation of the ICCP system was roughly $1.7 million, which was five times less than full replacement. Today, 12 years later, the building is in pristine shape and free from major restoration. This 12 year period represents at least two restoration cycles that were prevented, a conservative cost savings of $3-4 million. Other than routine annual maintenance, re-application of wear coat, etc., 2100 Towers has not had to spend any additional dollars on major concrete repair due to corrosion of reinforcing steel. In the end, the motivation behind 2100 Towers decision to invest in an ICCP solution were the following:

  • It was the most cost-effective solution.
  • Multiple Engineers that we consulted with recommended the system
  • It has a design life of 25 years and came with an unmatched 15 year no-corrosion guarantee.
  • It was proven to work long-term and was backed by independent agencies like the FHA, NACE, and the DOT.
  • It would prevent corrosion from infiltrating inside the units.
  • The homeowners would be able to avoid future restoration projects that lead to additional expenditures on sliding doors, and shutters that were out of code.
  • The homeowners were able to avoid future restoration projects that create an environment of noise, disruption, dust and debris, loss of rental income, quality of living, and everyday inconvenience.

Julie Wages, 2100 Towers, Property Manager stated,  "I was here through all three major restorations, we are proud of this award and are looking forward to continued cost savings with the solution and installation." "



Copyright 2008. Cathodic Protection Technology. All rights reserved