How To Fix A Crack In A Concrete Pool
Fixing cracks in a concrete pool structure is definitely not something that you want to have to do as a pool owner. It takes something fairly serious to go wrong to result in a crack to develop in a concrete pool. Perhaps even a series of things going wrong, and the reality is that pretty much all of those things are impossible to fix after the fact. Once a concrete pool has cracked there is no repair process that will fix it indefinitely. The reason why you can not fix it is because something has gone wrong to allow this to happen, and if this problem continues to exist then any repair is sure to fail as well. The original shell cracked and any repair you make is sure to be less-strong than the original shell.
So in one sense there is nothing you can do to repair a concrete shell. It broke once and if it wants to it is going to break again. However there are a lot of concrete pools out there that experienced a crack decades ago and while there is not a proper repair for this the truth is that the crack has not migrated in years. Decades perhaps even. In these situations I still warn concrete pool owners that something caused the pool to crack originally and no repair you make now of installing a new pool shell will really resolve this. But if they have been using the pool for years like this, and simply do not have the budget to put a new pool shell in, then advice explaining that this crack can not be fixed will fall on deaf ears. Usually the pool owner explains that they have no choice but to live with the crack, and so they want to do whatever they can to improve the situation.
Filling concrete cracks with silicone - The reason why I am writing this article is because pool owners often attempt to inject silicone into concrete pool cracks. They know they can not fix the problem properly and so this is the suggestion they come to me with looking for guidance as to whether this will work. It will most certainly not work. In theory some kind of sealant to prevent water from escaping through the cracks would be a good idea but silicone is definitely not the right stuff for the job. It is way too light duty, does not bond to concrete well enough, will not withstand any hydrostatic pressure, does not bond when there is moisture...a total fail for this application. Look, injecting cracks in a concrete pool is a bandaid solution at best, but if you are going to do something to try to improve this problem you need to choose something with a little more staying power than silicone. Even type two silicone suitable for damp applications is still not durable enough for this application.
Filling cracks with concrete urethane - A concrete urethane product is like silicone on steroids. It sucks to works with, does not clean up with water, sticks to absolutely everything...basically it is perfect for injecting into cracks in concrete pools. A new structure is obviously a better option than patching up a failed structure, but that is serious money that most people simply do not have to spend. When used properly, and as part of a multi-stage approach to filling cracks in a concrete pool, a concrete urethane can give you a real shot at success at resolving the leaks from the cracks in the long term. There are a few products that you could use for an application like this.
So what would be a good product to use for something like this? A concrete urethane called Deck-O-Seal would be a great option to use. It is a very demanding environment and there are not many sealants that are perfect for this job. Another one that I have used for applications like this is NP1 Polyurethane.
How To Fix Cracks In A Concrete Pool
Understanding that filling a crack in your concrete pool with urethane is not really a long term solution you can count on, it definitely beats the heck out of just using silicone. So let's explore this further and identify what else you can do to improve your chances of slowing or stopping water from escaping through this crack. Typically speaking the process I use is to first cut a channel into the area directly on either side of the crack itself. Ideally this should be about one inch of concrete depth that I am aiming to remove. When doing this the cut is very specifically angled to create a "U" shaped notch which will aid in the next steps, which include adding a hydraulic concrete to this channel we are cutting out.
With a channel cut on either side of the crack, I will often run the grinder along the crack itself, creating a groove which I will inject and fill with urethane shortly. Before doing this I usually take a strong garden hose or pressure washer and wash out the crack and channel that I have cut. Concrete dust will prevent both your urethane as well as the hydraulic cement from bonding properly. Spraying it with water works great to get rid of the dust, but you also want the area to be expressly dry before attempting to use the concrete urethane. Even leaving the crack overnight can result in dampness being held along the crack, and so compressed air is the best bet to blow all of the dust remnants out and dry out the crack. Even a tiger torch to heat up and dry the area would be a good idea before using the urethane.
Injecting the urethane into the cracks - Be sure that you have done all of the proper prep work as described above to the crack before proceeding with the urethane injection. We are already not taking the right approach here so it is the least you can do is make sure the crack is totally dry and free of dust before proceeding. Be sure the urethane tube is warm, even a little on the hot side as this will make it much thinner and able to be pressed into the crack with some measure of success. Concrete urethane is messy so be sure to have plenty of rags on hand. Warm urethane should flow fairly readily into the cracks, but you will never get as much into the crack as you would hope for. Leave a bead of the urethane covering the crack itself to be sure that you have actually sealed it. Follow the cure time instructions from your product, which will likely be a day or more for the urethane to fully cure.
Applying hydraulic cement to the U channel - The urethane along the exposed crack should in theory be enough to stop water from escaping the pool and also absorb slight amounts of movement in the concrete moving forward, however if there ever is a time to take all the steps you possibly can, this is the time. The U channel we cut into the concrete serves a very specific purpose. Almost all concrete products shrink when they cure. Hydraulic water-stop concrete does not shrink and actually expands slightly when curing. This combined with a massive dose of bonding agents and polymers help hydraulic cement to stop water. By using the expanding nature of concrete to our advantage, the shape of the U channel should trap concrete from your patch which then has no place to really expand to side to side. The result is that the patch of hydraulic cement really wedges itself in place, which serves to make a more water resistant contact point then you would normally see with a cold joint in concrete (new concrete attaching to old concrete).
Make sure you use the right hydraulic cement product for this application. There are a few brands that make suitable products for this. One example is this hydraulic cement. If the product that you are looking at indicates a very fast set up time, as well as the ability to stop water leaks, this should do for your application.
It might not be perfect, but if you are trying to fix cracks in a concrete pool then exposing the crack, cutting a U channel, cleaning and drying it, injecting warm urethane, and filling the channel with hydraulic water stop cement is as good of a bandaid repair as you could possibly hope for. Something like this actually stands a reasonable chance of improving your situation, something that injecting with silicone was surely not going to do for you. With this reasonably strong patch now in place, let your concrete repairs cure for 28 days before applying a new interior surface layer to your pool, plaster or paint, to cover the unsightly crack repairs.
If you have cracks in a concrete pool I would strongly encourage you to reach out to an industry professional for guidance as there could be more serious issues going on with your pool than you realize. If you are not going to take that good advice and are going to just squeeze some silicone in the cracks and hope for the best then you should at least use my method with the concrete urethane, U channel and hydraulic cement.
How to bond new concrete to old concrete
Common problems with concrete pools
How to fix pool tiles that are falling off
How to work with concrete
Maintenance and repairs for concrete pools
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