Concrete Ponds

Sometimes concrete ponds are constructed and virtually no thought is given to how the surface should be in regards to it being able to accept a waterproofing coating later.  Sometime the surface is either too smooth or too rough and needs to be corrected prior to applying the coating.

I have seen people use brick in the ponds also.  Now brick is a funny material.  It is either too porous or ultra smooth.  Porous brick is not usually an issue because the pore can be filled, but ultra smooth brick can cause future delaminating if it is not properly surfaced prior to coating.  The techniques to handle this type of brick would be the same as with concrete to be explained here.

I find that one of the easiest ways to make a smooth surface more rough is to sand blast it.  Of course sand blasting has its pros and cons.  For one thing, it most certainly will clean a surface pretty well and give a nice texture to accept a coating, but it also makes a serious mess.  You’ll end up with sand everywhere and it will be there until your surrounding yard assimilates that which couldn’t be cleaned up.

Also with sand blasting, you’ll have to hire someone to do it.  It’s not likely you own the equipment necessary and probably do not have the skills either.  That is ok though, because there is at least one other way to accomplish this.

My favorite way is to use a large 8” angle grinder.  Suit up in protective eyewear and a face mask and you can go to town with a tool like this and either smooth out the concrete or rough it up as needed.  They work wonders.  Let me explain.

If you use a flexible sanding disc on an 8” angle grinder it allows you to cut away imperfections in the concrete while at the same time protects the concrete from you accidentally gouging to some degree.  This means you can float the grinder over the surface and follow the natural contours more closely without cutting away too much concrete.

Use a 24 grit sanding disc for the process as it will leave a more desired surface afterwards.  Not to mention it will last longer since it is coarser.  Be sure to aim the spin of the grinder away from yourself.  There’s no sense in directing debris right at yourself.  It not only hinders your sight but the flying debris can injure you as well.

Take Gunite for instance.  Usually a Gunite installer will assume that you plan to apply a plaster coating to the new pool or pond and he or she will normally apply a broomed finish to the Gunite surface.  That is fine and dandy for a plaster surface, but no good for applying a coating.  If you apply the coating to a surface like that, you are likely to waste a bunch of material just trying to fill in-between the broomed gaps.

Finally, as I said before, this scenario works fine for smooth brick too.  If you can just give the brick a new surfacing, it will give the coating much more to grab hold of during the application process, which will give you a longer life with the coating.

Keep in mind that this process will also be helpful when smoothing out mortar joints too.  Sometimes masons can get a little slopping with their joints and there’s no reason to just coat over them as is.  Clean them up first.

Over time concrete can crack.  Ground movement, concrete shrinkage, freeze/thaw conditions can all play a part in possible cracks forming in your pond.  The trouble is that when they happen, you have to go out there and fix the problem.

So how do you go about fixing a crack in a pond?  Well that all depends upon the type of crack as well as the size of the crack.  Cracks can be anything from small hairline cracks up to large fissures that go right through the entire structure.

The simplest of cracks is just a hairline crack.  A crack like this can be easily repaired using the right materials.  However, using the wrong materials can easily lead to that hairline crack turning into something far worse.

Far worse simply means more resources to affect the repair.  Cash and time are things everyone wants to avoid dumping into repairs so taking your time to think the situation through is very important.

Let’s say you have a crack.  The first thing you should try and do is determine how bad the structure has been affected.  If it is a hairline crack, it probably does not go through the entire structure, which is good for you.

If the crack goes through the structure you might have your work cut out for you.  In severe cases there isn’t a lot of repair that can be done.  But those instances are pretty rare if the structure was made using all of the proper elements needed for good, sound construction.

There are several types of materials that can be used for repairing concrete, including, more concrete, concrete strengthening additives, bonding agents, rebar, steel mesh, epoxy (like Pond Shield epoxy) and fiberglass.

Most people tend to lean towards applying some sort of rubberized caulk into the crack.  The problem there is that rubberized coatings or caulks do not bond very well to concrete and can peel.

You also end up with a crack repair that continues to move and can eventually fail again.  You really need to shore up the concrete so that it acts just like it was when the crack did not exist.

For hair line cracks, an epoxy like Pond Shield can be used to coat over the crack.  Coating over a crack will give you the most minimal resistance to the crack reappearing.  I suggest that you use a grinder with a cutting wheel to groove the crack and THEN fill it in with Pond Shield.

What you end up with at that repair is essentially a concrete stitch.  The epoxy holds the crack from both facing sides as well as across the top of the crack.  Pond Shield tensile bond strength (that exceeds the internal strength of concrete) combined with its elongation break strength of 9,500 psi will pull and hold the concrete as though it were once piece.

For larger cracks, like those that are a half inch or so wide, you’ll have to consider more drastic measures.  You may find yourself cleaning up the crack quite a bit by actually removing portions of concrete so that you can place new concrete into the affected area.

If you cut through rebar or steel mesh, you will have to put new rebar or steel mesh back in.  Rebar and mesh help strengthen concrete as a whole.  If you have to replace pieces of rebar, you can drill into through both sides of the crack at an angle so that you might glue new rebar in place.

After the stitch is in place, you can use concrete to fill in the crack.  You concrete can have fibrous additives in it that will act as a strengthener.  Be sure to use a good bonding agent on concrete before filling it in.  This will aid in the adhesion between the old concrete and the new concrete.

Once the concrete has set up and cured properly, cut the rebar off that is sticking out of the concrete.  Make sure to try and cut it lower than the surface of the concrete.  Then apply your epoxy to seal the rebar and prevent any corrosion.

Because concrete is porous, I recommend that you coat the entire surface that will be submerged in water.  This will keep the water from soaking through the concrete and reaching the rebar beneath where it can corrode there too.

For added strength, you can also apply a strip of fiberglass over the crack as well.  Just apply the strip while the Pond Shield is still wet and saturate it out completely.  Once cured, the complete repair ought to be much stronger than the original concrete was.

Bear in mind that with any coating application you will want to make sure that the concrete has been properly acid etched prior to the repair.

Did you know salt water was corrosive?  It is.  In fact it is a problem that engineers have been faced with for some time in regards to larger concrete structures like sea walls.  Of course sea walls are corroded by much more than salt, such as sand and gravel kicked up and splashed against the concrete.

Salt water itself contains magnesium chloride, sulfate ions and hydrogen carbonation ions that will essentially attack concrete to a certain degree, but what really starts to corrode in a concrete structure is any of the steel substructure within.

Concrete contains an alkaline environment that provides some protection against corrosion. The steel inside the concrete that is used for reinforcement will react with the concrete and form film that protects the steel.

This is where salt water works against that process.  The chloride and sulfate ions will weaken that film as the water soaks into the concrete.  Once the film is breached, then the corrosion process begins to work on the steel itself.

Have you ever seen rust stains coming out of concrete?  Usually these stains appear around a small fissure or crack.  The fissure or crack would have been the most likely place for the salt water to enter.

Because concrete is a type of porous material, oxygen and humidity can be present at the point the salt water has come into contact with the film.  This is when the corrosion process of the steel will begin.  This is also the point where things can go bad.

Now granted, this is not an over night process.  Generally this process is gradual, but environmental conditions can accelerate the process.  Building a holding tank for saltwater aquaria risks this sort of corrosion if not properly protected.

Going back to the steel in the concrete, this being wire mesh of rebar, this normally just a simple carbon steel.  When carbon steel corrodes, it expands.  Have you ever found something old that’s made of steel that has become all rusty?  You recognize the item, but it’s usually a lot bigger than it was when it was new.

The problem with the steel inside your concrete tank is that as it expands, forces will be applied to the concrete structure that causes it to crack.  This in turn, leads to more of the corrosion process to begin.  At some point, if not cared for, the concrete will totally fail.

As I said earlier, corrosion of this sort will surely destroy concrete over time unless it is properly protected.  You need a barrier between the concrete and the salt water that will stop water, chlorides and oxygen from reaching the inner working of the structure.

Pond Shield epoxy has been formulated to do just that.  It has been tested in a variety of corrosive environments, including salt water to ensure that it is capable of performing this important task of protecting the concrete.

There are many types of concrete pond sealers on the market today and the biggest problem for anyone looking for one is to know how to find the best product suited for the project at hand. You can search the internet and find a huge variety of sealers, but you have to ask yourself a few questions first.

• Which one is right for your application?
• How do you know what to ask the sales representative when you have questions?
• Will the coating harm my fish?
• How long is the sealer supposed to last?

Well follow along and I will try to help you with choosing the right sealer.

The first thing most people should realize about pond sealers is that there are big differences between products that claim to be a sealer and those that actually are sealers, and by that I mean something that waterproofs. Typical concrete sealers are just a way to keep water from soaking in. They are sometimes oil based and usually have to be re-applied each year.

Knowing whether the coating is non toxic or not is very important when choosing a sealer because you need to make sure the sealer is safe for fish and plants if you plan to house aquatic life. There are many pond sealers on the market today that will seal a pond up just fine but can be deadly to aquatic life even after the sealer has cured. You certainly do not want to loose your stock.

Next you need to think from an engineering stand point. Because there are so many different sealers out there, the actual properties of the sealer you choose can mean success or failure of your project. A few things you might want to keep in mind are tensile bond strength, elongation break strength as well as the quantity of solids that the actual sealer is made up of.

Did you know that certain types of solvents in a sealer are listed as volatile organic compounds (VOC)? VOCs are not only harmful to the environment, but they can also harm your aquatic life.

The tensile bond strength of the sealer you choose should be strong enough to not peel later. A peeling sealer will only cause you more problems later when you have to repair the problem. Pond Shield epoxy, for instance, has a tensile bond strength that exceeds the internal strength of concrete, meaning it is not going to peel or flake off of a properly prepared surface.

Elongation break strength is closely related to the flexibility of the sealer. Elongation is the material’s ability to stretch before breaking. The break strength is how much force must be applied before the sealer breaks.

Everyone knows concrete can crack, so the trick is to find a sealer that will resist mimicking any cracks that may want to form. This will ensure that after the sealer has cured, hairline cracks that can form do not transfer through to the coating.

Going back to tensile strength, this is where most rubberized coating can have issues. The movement is too much for the coating to bear as it stretches causing the tensile strength the fail, later causing a peeling issue. Sometimes this looks like a bubble in the sealer.

Finally, there is the amount of solids that the sealer contains. This is very important. The reason is because a sealer that does not contain 100% solids in its makeup will then contain solvents and such instead. Remember, I referred to these as VOCs.

The problem with a pond sealer that contains solvents is two-fold. First, solvents might actually be toxic to aquatic life. Remember, just because a sealer is cured, does not mean it is not leeching off toxins into the water.

Pond Shield epoxy is tested for toxicity is both its cured and uncured state to ensure that it will not harm aquatic life. Finally, pond sealers that contain solvents are also prone to shrinking during their curing process. What happens is the solvent evaporates out of the sealer and the over-all body of the sealer shrinks and a crack may form.

So pick a sealer that actually waterproofs, has no VOCs and is non toxic to the aquatic life you plan to house.

We come in contact with it every day in some shape or form. It has touched the lives of the human race since 5600 BC when ancient Serbians used it to construct huts. A thousand years ago, the pyramids of Shaanxi were constructed with a form of concrete. Assyrians, Babylonians, Egyptians and Romans all had their own forms of concrete.

That is until, at one point in history, the recipe for concrete was lost to mankind for some 13 centuries. Did you know that it was only just rediscovered in 1756? That’s right. Up until then it was lost!

It is all around us and for what we take as nothing more than just another one of life’s everyday occurrences, it is pretty special. Concrete is used for bridges, buildings, dams, roads, furniture and yes, even our favorite, ponds.

Now that concrete is the center of your attention again, do you ever wonder how it works?

Bah! Maybe not, but that is ok. I will give you a brief description of the inner workings of concrete anyway and with any luck, and if you’re actually planning a pond project, you’ll be better armed to make those concrete decisions about your pond. Please excuse the pun.

Basically concrete is a mixture of cement, aggregate and sand. Cement is made from limestone and calcium sulfates which in essence becomes a binder for the whole mess. Sand is used as a filler and the aggregate is used for strength.

When water is added, it is used to start the curing process, which is also known as the hydration process. This curing of the cement in the mixture is required before the concrete acquires its final strength. During this time, the environment should be controlled to allow this hydration process to take place. This can best be accomplished by keeping the concrete moist for the duration of the hydration process. In doing so, the risk of cracking will be minimized.

Different chemical admixtures also play apart in how concrete works. Typical admixtures are,

• Accelerators
• Retarding agents
• Plasticizers
• Corrosion inhibitors

All of which will affect the outcome of the final product. A speedier curing process, a stronger concrete or a more flexible concrete are just some of the results these additives will produce.

Now it is best to attempt to pour all of the concrete for a single structure in a single pour. This is because once the concrete cures, it is unlikely that the bond between a new pour and an old pour will be even close in strength as a completely poured unit. On the other hand, if the need is there to put the concrete down in multiple pours, then a very good bonding agent should be used to assist in connecting them together. Keep in mind though, that even with the binding agents, these joints will still be weaker than a solid piece of concrete.

There are two important things to remember when applying Pond Shield. First is surface preparation, but the second thing is the easiest to skimp on, that is inspection.

After your epoxy coating has cured, you need to take a look at every square foot of your pond to make sure you have coated everything that will be submerged. Sometimes while applying a coating, small areas of your surface area can be missed, like those in the pictures below.

Small Pits and Holes

Large Pits and Holes

Whether in the form of a little concrete (or whatever surface you are applying to), showing through because the coating was applied to thin, or little holes, voids or crevices, these can all turn out to be potential leaks. You need to make sure that you are not simply applying coating around these areas and calling it a job done.

After your coating has cured and you can move around on it, you should take some of the Pond Shield you retained for touch-up and fix any spots where your surface area shows through the coating and any holes, voids and crevices. Keep in mind that if your surface area has larger holes, you may want to correct them before you apply Pond Shield.

When mixing concrete for a specific project there are a few things you should keep in mind. First, it is important to know what soil type you plan to pour your concrete into. Different soils such as sand or clay offer very different load bearing qualities for your finished structure. Because of this, the type of aggregate used in the mixture needed for your project will vary.

It is equally as important to correct and issues your soil may have in regards to how compact or loose it is before pouring concrete. In some areas, it is recommended to have a survey soil taken in order to best deal with any issues the soil type may pose. These surveys are used to check soil type and density that will ultimately tell you how to properly prepare the ground before your concrete pour. Failure to do so can result in cracks forming in the concrete as the ground settles.

The other important aspect of concrete mixtures is determining how strong the structure needs to be. For instance some people consider a typical mortar mix to be concrete and just as strong as any other concrete. This is not true. Where a mortar based type of material contains cement and water like concrete, the aggregate used in mortar is usually nothing more than a fine grade of sand.

This will work fine for joining two blocks or bricks, but has virtually no real strength properties. Aside of the fact that you’ll have to run some sort of steel wire mesh and/or rebar in the concrete, the aggregate choice you make will determine a lot of the strength properties of the finished product.

It can be said that one of the real strengths of a good concrete mixture is the size of the aggregate in the mix.

As an example, a nice 4 inch slab of concrete might utilize 3/4 inch rock as an aggregate. The binders in the cement and sand will hold the rocks tightly together to form a stronger stone like substance. Because of this, the rock size will definitely ensure more strength, but that does not mean if you poured the concrete mixture out at 3/4 of an inch thick, that 3/4 inch aggregate would be suitable.

You have to make sure that the thickness of the concrete mixture being poured is enough to properly encapsulate the stone aggregate. Otherwise, you’d end up with a thin layer of concrete that consists of nothing more than cement followed by a rock, followed by cement which would not be very strong at all.

There are also a variety of admixtures that can be blended into the concrete mix. Some of these will assist in either accelerating or retarding the curing process. Others like fibers, will add to the sheer strength of the finished product. Of course there are also

• Air-entrainers
• Corrosion inhibitors
• Bonding agents
• Pumping aids

These are all designed to improve both the way the concrete is applied and used. Fiber reinforced concrete is made by adding fibers that are typically made of steel, glass, synthetic or natural processes. Each of which will add a certain amount of strength to the concrete after it has cured.

It is always recommended that you consult your local concrete manufacturer and discuss your soil type and the needs of your project. They usually have several formulas on hand to choose from that should suit your needs.

The surface area you apply Pond Shield to should be smooth in order to get the full coverage of each kit. The best way to explain this is to compare a ready to coat surface to that of 60-grit sandpaper. If your surface area resembles 60-grit sandpaper, you should not have a problem obtaining maximum coverage and there will be enough tooth on the surface area for Pond Shield to adhere to. The picture on the top is what you should be looking for in regards to surface smoothness.

Smooth Concrete

Exposed Aggregate

While rough surfaces can still be coated, you should plan for extra Pond Shield as those uneven surfaces like the exposed aggregate. Shown here, exposed aggregate will use up some of the square footage allotted for your project. Pond Shield will cover areas like this but in extreme cases you can correct a problem area by applying a bonding agent to your surface area and then a smooth concrete render over than.

Choosing a proper concrete bonding agent is important so that you do not have problems with the render not sticking properly and eventually falling off of your concrete surface. If the render falls off, any Pond Shield you applied to that render will come off in the process so be sure the render is bonded well.

So you’re at the point where you’re about to prepare your pond for a coating. What the heck is acid etching?

Acid etching is the process by which your concrete will be cleaned and prepared prior to actually applying a coating. Learning how to acid etch a pond is easy, but I’d like to explain the reason for acid etching a little more in depth before we talk about how to acid etch a pond.

All concrete will go through a hydration process for a period of time. The hydration process is essentially the curing process of the concrete. This period of time is usually about the first twenty eight days for normal concrete and sometimes less for more specialized concretes.

During this time the concrete will effervesce, expelling gasses into the atmosphere. The process can be likened to the carbonation process of a carbonated liquid beverage, but on a slower scale. When this hydration process takes place, powdery deposits are formed on the surface of the concrete sometimes referred to as efflorescence.

This efflorescence comes from the calcium sulfates that were used in the cement that was part of the over-all concrete mix. The one thing all of these deposits have in common is they will all more than likely fall off of the concrete over a period of time. Some of these deposits are not readily visible either. The concrete may look clean, but these deposits still exist.

The problem that arises with this if you apply a coating that bonds to the deposits instead of the concrete, when those deposits fall off, so will your new coating. So it is imperative to remove them by this process of acid etching.

Finally, the process of acid etching will also mar the surface of the concrete to some extent. This marring is actually good because if you had a perfectly smooth concrete surface, the coating may not have much to grab hold of when it is applied. This marring usually makes the surface of the concrete feel about as rough as 60-grit sandpaper. A surface like this will allow a coating like Pond Shield epoxy to grab hold with thousands of tiny little fingers and not let go.

The acid etching process is easy to do.

Muriatic acid can be purchased at almost and pool supply store or hardware store. You should use a mixture of one part muriatic acid to three parts water. Then apply the mixture to the surface of the concrete by either brushing or spraying it on. You should use a brush to work the mixture in a little, but no real elbow grease needs to be applied. The acid will do the work for you.

Additionally, make sure you are wearing proper protective clothing and eyewear and gloves while performing this job. Safety first!

Once you have acid etched the entire surface, you simply rinse the pond off with fresh water. You can use baking soda to finish neutralizing the acid/water mixture that ends up in the bottom of the pond and then dispose of properly. If you’re not sure how to dispose of the mixture, contact your local municipality and they can direct you. That’s all there is to acid etching a pond.