Introduction of Spalling Concrete:
Spalling of Concrete is a common issue that occurs in the old structure components in which the surface of the concrete peels and breaks away.
In this article, you will learn about spalling concrete and how to prevent spalling concrete so read the article at the end.
What Is Spalling Concrete?
Spalling concrete definition: Spalling of concrete is a crack and disintegration in the area of concrete. It is caused by freezing cycling, effects of alkali silica reaction or damage from exposure to fire.
Concrete spalling or spalling of the concrete alludes to concrete surface breaking apart, which stretches beyond the layers of reinforcing steel(which was inserted when the building was getting erected).
These spalls may be anywhere from 150mm to 170mm in diameter and 25mm or more depth-wise. These, however, don’t exempt the possibility of smaller spalls as per ACI 302.
Spalling of concrete leaves such cemented surface patchy and pitted while pushing aggregate underneath to the forefront for attacks. Things will exacerbate if such spalls aren’t attended to on the dot, these should be thoroughly repaired.
Failing to do this may lead to perturbed concrete surface integrity and puts the ultimate capacity of the member at the brink. And who can ever forget the distorted look of beautiful structures, thus affecting its external beauty.
Causes of Concrete Spalling:
There are various causes of concrete spalling which are as follows:
Concrete spalling, or as we call it falling apart of concrete, is caused due to several reasons that we will be listing down in this article.
The causes are mentioned below:
- The first and the foremost reason that makes concrete/cement come to bits and pieces is attributable to the corrosion of those installed reinforcement steel, for these corroded materials tend to occupy more volume than the non-rusted or original steel, and the pressure isn’t borne by concrete which leads up to it falling into bits.
- Sometimes concrete gets exposed to fire which results in concrete to stem, thereby putting expansive pressure in concrete. It goes without saying this makes up the major reason behind concrete spalling.
- Next up we have, freezing and thawing cycling which ruins the aesthetic of beautiful structures by creating crevices/fissures.
- The daunting and expansive effects of the Alkali-Silica reaction also cause cemented surfaces to come apart.
- Another reason why your concrete surface may be spalling is low quality and poor coating of concrete or cement over the reimbursed steel(inserted while the foundation was getting laid).
- Many a time you find joint spalls which may be ascribable to the improperly erected joints.
- Due to insufficient depth of cover over the reinforced area that causes the structures to have spalls and they become prone to such attacks.
- Lastly, the reason behind such spalls can be found in bond failure in two-course construction. This may be due to the gap in shrinkage between two courses; topping and base ones, maybe the topping concrete is spread out even before the bonding grout dried, etc.
- The use of low-quality concrete cover and the expansive effects of Alkali-Silica Reaction can cause spalling concrete.
These are the causes that may be affecting the look of your structures and the weakening of the foundation.
What Will Happen If My Concrete Is Spalling?
The consequences of concrete spalling are self-explanatory. The primary downside of such spalls is that it makes your structure look unattractive, thus exposing you to all sorts of criticism and judgemental looks.
The situation certainly worsens if the concrete spalling is in an area that is accessible/used by the public, or by workers, to cross places within the residential building, as there are high chances of debris bumping into their heads.
If the concrete spalling isn’t treated immediately, it would spawn across the area, thus leading to an unstable structure of the building. This is precisely why it is admonished to inspect the buildings and maintain them. Only owners can make sure of such perilous things, capable of taking lives.
If we turn our attention towards the commercial consequences of such spalls, we come across the decreased value of assets boasting such dangerous fissures and spalls. Further, there’s a proliferation in the maintenance cost if corrosion and concrete spalling are seen in more than a place.
Structures that are highly pervious to the eyes of customers include car parks, where the users will avoid commuting at any cost due to the hazardous outcome outlined above.
How to Prevent Spalling Concrete?
You can always take corrective measures to foil the possibilities of these spalls from taking over your concrete/cement surfaces. This section will be dealing with the same.
To prevent moisture-related concrete spalling, the best way is to seal the area and that’s how you will stay untroubled. As for new concrete, you will be needing a waterproof sealer. Apply this penetrating waterproofing sealer 1 month after you are done coating the surface with concrete. This process must be carried out every few years so the chances of spalling dips below negative.
Another way that may surprise you is the correct ratio of a concrete mixture. In order to provide resistance to freeze-thaw cycles, air entrainment can do wonders to help with the spalls.
When the moisture present in concrete (especially in those crevices and rifts) freezes, these air cells help get the internal pressure off. This is done by microscopic chambers which help expand water as and when it freezes.
The spalling concrete can be prevented by using air-entrained concrete and proper curing the concrete. These are the only two ways, at your disposal. Adhering and being mindful to both of these preventive measures will help you in the long run.
How Do I Repair the Concrete Spalling?
If you didn’t take the preventive measures discussed just above this section, then you are left with the repairing and fixing option only which can be quite an unfathomable task to become fathomable.
Concrete spalling repairs should necessarily be carried out in compliance with BS EN 1504, which stands for the European and British Standard for the repair and protection of reinforced concrete.
The medium, or the contractor, must diligently be reached upon and he/she must be suitably qualified, having all the skills necessary to fix the big spalls. The use of such contractors holds the same significance as diligent substrate preparation. Further, the filtering of a repair material that goes well with the host concrete is also necessary.
Fixing of such spalls will be carried forth by making use of pre-bagged materials, that make sure of consistency and components compatibility. The materials needed are available in different forms, namely flowable/hand-placed or they may be readily feasible as a spray application, and this hinges on the size and geometry of the application.
Regardless of the intentions of whoever is carrying out the repairing process, concrete patch fixing more often than not, fails prematurely, on grounds of corrosion which in and around the periphery of the repairs. So firstly, this corrosion must be dealt with or you can easily control it by getting CPT PatchGuard™ galvanic anodes installed.
These are usually installed at 500mm centres into previously small drilled holes along the inside edge of where the repairing takes place, where each of this PatchGuard™ anode is individually linked with one another, through an integral tie wire, to the susceptible steel within the area where spalls are prominent.
These once connected to the steel reinforcement, the PatchGuard™ anodes generate a form of galvanic current which makes the steel relatively cathodic where the effect is obvious to manifest. This prevents fissures and the formation of crevices in the area of repair.
The corrosion is inevitable, PatchGuard™ anodes will slow down corrosion as per the steel installed. This is exactly why these are also referred to as “sacrificial anodes”, for they bear corrosion. These PatchGuard™ system has been proclaimed as an effective way to foil the so-called “incipient anode”, or “ring anode”, out-turn and help prolong the patching spalling concrete life so that you won’t have to splurge out money again and again.
Talking of sound but unfiltered areas of concrete, CPT Patchguard Connect™ anodes can be set up to thwart the possibility of further spalling. The first step of pushing the anodes into drilled holes in a grid form leaving out 500mm space, remains the same.
The difference lies in the fact that PatchGuard Connect™ anodes are wired together i.e. 20 anodes are held up together and thereafter it is affixed to the exposed area of steel. The best part of this approach is that it clamps down the need for exposing multiple sheets of steel. Once the above steps are performed, the wirings are ultimately faced with saw cuts.
Now, the PatchGuard Connect™, like in the earlier paragraph, makes use of the same. purely galvanic technology and oils the wheels of maintenance-free corrosion protection and it goes beyond existing patch repairs.
One of the biggest merits of the PatchGuard Connect™ system is that it lessens the probability of corrosion especially of the exposed areas, thereby reducing future spalling concrete repair cost that one will be splashing out money for.
Both the PatchGuard™ and PatchGuard Connect™ systems won’t let anything touch the concrete for at least 10 to 20 years, though this highly depends on how the local conditions are.
Now it is time to address the not-so-favourable side to galvanic anodes and it is that the properties possessed by sacrificial alloy place a ceiling on the voltage available to generate power for the system. Many a time, these galvanic systems are more than enough for clients as they provide long-lasting effects and untroubled maintenance.
However, in the conditions where the environment isn’t as calm as we supposed it to be, there’s a pressing requirement for a higher driving voltage to slow down and stop corrosion and shield the steel by putting up a layer upright.
In order to address these disparate needs, CPT came up with DuoGuard™ which seems to be of use, for it caters to every need by being the world’s first-ever hybrid corrosion protection system.
These DuoGuard™ are charged or powered by a source that lies external to them for 7 days before it goes back to purely galvanic mode. These also stop areas where corrosion is very prevalent.
Further, just like the previously dealt systems, these too have a 20 years life span.
Spalling Concrete Repairing Cost:
Now one may muse on the cost that owners will be set back by in order to repair these spellings. The cost varies from method to method. If you decide on a concrete resurfacing spalling concrete resolve method, would the spalling concrete repair cost you anywhere between $2.50 to $4.00 per square foot. If the calculations are right, 100 square feet of resurfacing will set your wallets back by $250 to $400.
Repair of Spalled Concrete Slab:
The repair of spalling concrete repair is done in the following ways
- By removing the concrete at the spalled areas and then exposing the corroded steel reinforcement bars.
- Scrape and clean the exposed steel bars and use a wire brush in order to remove the rust on the reinforcement.
- Apply the two coats of the anti-rust paint to the steel bars and before patching the area, apply a proper bonding agent to the affected area surface in order to ensure proper adhesion.
- patching spalling concrete up the hacked area with the help of polymer modified concrete.