The Problem of Rebar Corrosion


If you have ever driven under the elevated portions of the Gardiner Expressway in Toronto, you probably noticed the litany of rust stains and exposed rebar visible on many of the expressway’s concrete support columns. These are the product of a structurally damaging process called corrosion.

Corrosion occurs when chlorides – primarily from de-icing salts in colder climates – penetrate concrete and reach the steel reinforcement causing it to rust. The volume of rust exceeds that of steel and over time, causes the surrounding concrete to crack and become damaged.

The safety implications of this process are apparent. You can google ‘concrete falls from Gardiner’ and find stories about chunks of concrete breaking off and falling on the roadways below. It’s easy to understand that this continuing deterioration is slowly compromising the integrity of the structure. To combat this problem, the City of Toronto has allocated $2.2 billion to fund the elevated expressway’s repair cycle over the next 10 years. This means that this cycle of repairs will cost 20 times what it cost to actually build the Gardiner in the first place.

So if corrosion jeopardizes safety, deteriorates structural integrity, and costs structure owners exorbitant repair costs, what is the solution?

Old Solutions versus New

For years, Calcium Nitrite-based admixtures have been the conventional concrete additive to accomplish this function. However, Calcium Nitrates have numerous drawbacks that forming contractors, ready-mix plants, and owners have worked around due to the simple fact that no viable alternative existed.

Here at Form and Build Supply, we constantly search for new, innovative products to bring to market. Products that perform better and solve problems. We’re proud to say that when it comes to corrosion-inhibiting technology we have found a superior alternative to Calcium Nitrites in the form of Cortec MCI® 2005 NS. This admixture product is integrated into concrete during the mixing stage and works to protect the embedded rebar from corrosive elements.

MCI® stands simply for Migrating Corrosion Inhibitors. This patented technology is incorporated into many of Cortec’s products and works by migrating through the concrete. When MCI® comes in contact with the embedded reinforcing steel, it has an ionic attraction and forms a protective molecular barrier around the steel. This barrier prevents corrosive elements from attacking the steel and greatly extends the concrete service life (see video for visual depiction of this process). Studies show that MCI® treated concretes have a corrosion rate that is 5 times lower than that of untreated concrete.


Benefits of Cortec MCI® 2005 NS versus Traditional Calcium Nitrites

For Calcium Nitrites to be effective, they require a large dosage rate to the concrete. This large dosage rate along with the nature of the product itself creates a number of problems for not only structure owners but concrete contractors as well. MCI® 2005 NS is the best solution to overcoming these challenges as illustrated below.

  1. Calcium Nitrites are Accelerators, Lower Air Content, and Increase Shrinkage Cracking: Due to their exceptionally high-dosage rates, Calcium Nitrites adversely affect concrete’s physical properties. Setting acceleration is one of these drawbacks and greatly reduces the amount of working time of the concrete. Forming contractors often experience quick or flash sets when using Calcium Nitrite dosed concrete in warmer weather. Calcium Nitrites also lower the air content in concrete which ultimately affects its durability. To offset these challenges, one must spend more money to add retarder and air-entrainment agents into the concrete mix. Additionally, Calcium Nitrates cause more concrete shrinkage which results in more cracking. This necessitates repairs on brand new structures. These headaches are avoided by simply switching to Cortec’s MCI® 2005 NS. It provides enhanced corrosion protection without affecting the set time or air content of your concrete.
  2. Calcium Nitrites require High Dosage Rates: For Calcium Nitrates to be effective they must be dosed at a substantially higher rate than Cortec MCI® 2005 NS. A lot of specifications provide for a Calcium Nitrate dosage rate of between 10 to 30 L/m3. In Ontario, there is a need for higher dose of Calcium Nitrites due to the above average presence of corrosive agents in the environment and extensive use of deicing salts in the winter. The higher dosage rate exacerbates problems previously mentioned. Cortec MCI® 2005 NS – on the other hand – is effective at a dosage rate as low as 1 L/m3 making it both more practical and cost effective.
  3. Calcium Nitrites Provide Inferior Long-Term Protection: MCI® stands for Migrating Corrosion Inhibitor. This describes how Cortec’s MCI® 2005 NS works. Its particles ‘migrate’ through the concrete structure and form a protective shield around concrete-embedded rebar. This shield protects the rebar from contaminants and reduces the corrosion rate by as much as 5 times versus untreated concrete. This ultimately extends the service life of the structure and reduces the number of required concrete repair cycles due to corrosion.

Already Enhancing Structures Worldwide

While MCI® 2005 NS and indeed, Cortec’s entire MCI®line of products are relatively new to the Ontario construction market, these products have been used in a number of high-profile jobs internationally. For instance, MCI® 2005 NS was used most notably in the podium substructure of the Burj Khalifa in Dubai – the tallest building in the world. The product was also used for a similar application in the Princess Towers also in Dubai.

MCI® 2005 NS’s use in this application represented 0.07% of the overall construction cost but effectively doubled the service life of the structure.
But the MCI® product line is effective in applications beyond towers and skyscrapers. Any civil application where the structural integrity of a concrete structure is vital can benefit from the use of the MCI® products. The Severn Bridge in the United Kingdom and the Cochrane Bridge in Alabama are two examples of where MCI® products were incorporated to protect the steel post-tensioned cables from corrosion.

Conclusion

Cortec’s line of MCI® products offer numerous benefits for anyone designing and building concrete structures. We’re proud at Form and Build to be the exclusive Ontario distributor for these products and look forward to talking with Engineers, structure owners, and concrete contractors about how this product line can enhance their structures and extend their service life.

To that end, we welcome anyone to reach out to us to schedule a lunch and learn or product demo. Please click here and enter your information and we will happily reach out to schedule a time to further discuss the benefits of our Cortec MCI® product line.

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Advanced Forms – What Can Forms Do For You?

Greg Rea, General Manager

Concrete forming literally builds the foundations on which our homes and cities are constructed. For almost 45 years, Form and Build has been in the business of providing the highest-quality products to the forming industry. Our knowledgeable staff have advised customers on forms and forming accessories that help get the job done faster and with less hassle.

The cornerstone of our company’s forming offering for many years has been the Advance Panel System. This system has many advantages over its competitors in the market. However, over the years, contractors have looked past these attributes and begun to look at forming panels simply as commodity products.
In this article I’m going to show that nothing could be further from the truth. The right set of panels can save you time, money, and last for years when taken care of properly. Specifically, the Advance Panel System stands head-and-shoulders above its peers. So I think it’s time that General Contractors, Agricultural Contractors, Forming Companies, and Landscapers all take a serious second look at this simple yet versatile system.

Price and Value

Did you know that an Eight-Foot Four Bar Advance Form currently sells for the same price – roughly $110 a foot – as it did in 1981? Over that same time period, wood and steel prices have tripled, wages have steadily risen, and the price of a house – the very structure for which the panels were initially designed – have increased fivefold. If an Advance Panel System was a good investment in 1981, it’s clear that it has become an even better investment today.

While General Contractors (GC) might not consider it worth it to buy their own set of panels, I would suggest we consider that question in the context of the residential construction market of 2019. This year has been a busy one. And sure, it’s nice to see healthy demand in the market. But if a GC is busy, then so are the forming subcontractors on which they rely. And if forming subcontractors are busy trying to keep up with their work, a GC’s timelines become increasingly dependent on their schedules.

So when you consider the costs of scheduling uncertainty, changing timelines, and delays, a GC investing in a set of panels of their own looks ever more prudent. Because the Advance Panel System is so easy-to-use, a General Contractor can take care of simple forming jobs in-house without relying on the availability of their forming subcontractor.

And what if you’re a GC that does a lot of steel structures? The four or five foot Advance Panel System may be of particular interest. With this system, a GC can easily construct pilasters into the wall of a building by using a few system panels and inside and outside corner pieces. A system like this can be obtained for as little as $65 per foot.

Quality

You can rely on the Advance Panel System to provide you with hundreds of smooth walls over their lifecycle. That’s because Advance forms are the only system readily available in Canada with a high-density (120/120) extra heavy-duty overlay to counter the abrasive quality of concrete. This quality craftsmanship also contributes to Advance forms lasting 10-20% longer than other competing products. Longer lasting forms ultimately reduce your cost. For instance, if you get 100 pours out of a system that costs roughly $100 per foot, that equates to $1 per foot of wall built.

Convenience and Versatility

The wonderful thing about the Advance Panel System is that it’s easy-to-use and can be used to tackle a variety of projects in the residential, agricultural, and commercial markets. Also, all of the hardware to lock the panels into place are attached to each form and corner piece. This means there will be no running around on the job site looking for wedges or keys that tend to get lost on each project.

While the eight foot four-bar system was designed originally for residential basements, the eight foot six-bar system can be utilized in numerous commercial projects. Twelve and sixteen foot walls are routinely formed with ease. The system lends itself well to stacking and the extra ties included on the eight foot six-bar system have the added advantage of being able to increase your pour rates.

Did you also know that you can form up to two foot by two foot columns with only four panels and four corners? No other system can compete with the speed and ease that the Advance Panel System offers in constructing such columns. One needs to simply calculate the time it takes to do so using standard formply, snap ties, and walers. You’ll be surprised how much faster you can accomplish this task with the Advance Panel System.

Conclusion

So whatever market in which you do forming work, consider whether the Advance Panel System could save you time and money. The professionals at Form and Build Supply are more than prepared to answer any questions you may have provide you with the best options available. And remember the ease and versatility of the Advance Panel System will eliminate your need for a carpenter on your next forming job.

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