I’ve written a few blogs in the past about repairing cracks in concrete, today I’d like to dig a little deeper and explain what product to use in a given situation and why.
While we provide concrete crack repair services and are happy to do so, these are jobs that many folks with time and patience can do to save money.
If you have used a product you feel good (or not) about feel free to leave a comment. This by no means is meant to be an exhaustive list of the products available, there just too many to review in a blog.
The one thing I wouldn’t use in any moving joint is concrete mortar. As soon as the joint moves it will crack and begin to deteriorate. Mortar is just fine for patching a rock pop or a missing chunk but not in a control joint or a crack. (accidental control joint)
Far and away the best way to stabilize a crack in concrete from movement is to “bridge” the underside of the crack with Geo-polymer foam. This is accomplished by making injections in a “stitch” pattern along the entire crack line. Then the crack can be repaired with confidence the repair will last.
OK, here they are –
Flexible Polyurethanes – for most exterior cracks flexible polyurethane caulking works just fine. In this line are fairly inexpensive products available at the big home improvement stores or the local hardware stores as well as some really good commercial grade products. We have used products from all three and have found them sufficient if not always long-lasting solutions. Also available from Quickrete is a liquid caulk in a squeeze bottle, bluntly put don’t waste your money on it. The solids settle to the bottom of the bottle and no amount of shaking seemed sufficient to break them down which resulted in clogs followed by an ejection of the material. Our current”go to” product is Masterseal SL1. Formerly Sonolastic brand, Masterseal is a superior commercial grade polyurethane. It adheres much better to concrete than the box store products yet maintains flexibility in a wide range of temperatures. The “SL” stands for self leveling so it is used for level or nearly level joints and cracks. (Not 45 degree angles) Masterseal also has products suited for sloped or vertical sealing if needed. (NP1) The average cost for DIY’er with this method is between $.50-2 a linear foot. Because this is a self leveling product you will need to fill wide or deep cracks with foam backer rod to reduce usage and waste. Masterseal sells a non off-gassing foam rope in two diameters that reduces bubbling of the material even if the rope is punctured.
Rigid Polyurethanes – these two-part systems are used for filling and structurally repairing interior cracks. Because they yellow when exposed to ultra violet radiation they are not good candidates for exterior cracks unless they are topped with another non yellowing material such as self leveling polyurethane caulking or Polyurea. This method is much more time-consuming and costly and some of the brands can only be purchased by licensed contractors. These materials are first injected into the crack allowing the material to absorb into the concrete which is followed by filling the crack with structural sand (silica) which is then saturated with more of the polymer. The material generates a thermal reaction so it sets in about ten minutes. When hard, the excess can be ground off with a finishing stone or a small hand grinder. Excellent for garages and other interior concrete the cost for a DIY’er is between $2-7+ a linear foot. Unlike Polyurethane caulking where you can greatly reduce product usage with the addition of foam backer rod, the ridged Polyurethane systems are designed to fill and adhere to the concrete top to bottom and completely saturate the sand filler in order to “weld” the joint back together. As a result the width and depth of the crack play a major role in how much material you will need.
Rigid epoxies – these two-part systems are in many ways comparable to the two-part Polyurethane systems spoken about in the preceding paragraph. They are applied the same way, both use Silica sand as a filler and both are finished with a stone or grinder. Epoxy can be used both indoor and out without concern with yellowing. So why would one choose a two-part Polyurethane over a two-part Epoxy? Both set up to about 4000psi, basically the same as concrete. The advantage that Polyurethane has its retention of a degree of flexibility which allows it to better adhere without developing a crack along the repair. Epoxy is brittle in comparison. Cost for the DIY’er is about the same as the two-part Polyurethane $2-7+ a linear foot.
With either the Polyurethane or the Epoxy repair any movement of the slabs along the crack line will crack the repair. Geo-polymer Slabjacking with the intent to bridge the crack greatly aids in stabilizing the crack.
Polyurea – another product to consider is polyurea, this is the same stuff they spray on pickup truck beds. It is extremely durable and also comes as a two-part system. The material is injected into the crack, if the crack is deep or wide I recommend a filler of some type as it is fairly thin, foam rope works well and sand can also work as long as you allow enough room for the material to adhere to the sides of the crack. Thermally activated this product sets up fairly quickly depending on the weather, ten to thirty minutes and according to the directions only an hour to drive on it. We have been very pleased with this product with one exception, the first little squirt needs to be purged into a waste container and as a precaution the last little bit of the set not used too. We have had some small areas not cure due to off ratio material which needed to be cut out and re-done. If done properly Polyurea hardens to the consistency of a hockey puck, adheres tenaciously and should last years. It comes in grey or black. The cost for a set of material is about $60 and will do between ten and thirty feet, again width and depth of the crack determining the difference. So $2-6 a linear foot, more if you use sand as a filler as it will absorb the material.
In addition to the mentioned products above there are Acrylic caulks, and ready mixed Vinyls that can be used. The ready to use Vinyl is difficult to make look good as it is applied with a putty knife not a caulking gun but it seems to work well on spalled concrete or to bridge gaps or to fill height differentials between slabs, for cracks I would stay away from it especially if appearance is important to you.
These are just a few of the available products available for crack filling and repair that we have used. Here are our top recommendations;
Exterior crack fill – Masterseal SL1 (long lasting crack and joint filler)
Exterior crack repair – Emecole epoxy for concrete repair
Interior crack repair – Roadware polyurethane concrete mender (contractor only)
Special purpose – Emecole polyurea (nearly permanent expansion joint filler)
OK, there it is. Whether DIY or hire 1-855-752-2522 we’re happy to offer helpful tips and where to buy information, call today,
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