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Epoxy Repair of Concrete Floors

Industrial Floor Maintenance with Epoxy

Preventing and Fixing Deteriorating Floor Joints and Potholes

It is said that there are two types of concrete floors, those with cracks and those that are going to crack. Cracks and potholes in plant and shop floors are a major problem to safety and aesthetics. Here we will discuss what causes them.  We will also discuss how to repair them quickly and economically. For those floors that have not cracked we will discuss how to minimize or prevent the cracking and potholes.

It is a common misconception that heavy loads on the floors cause most flooring problems, and so it cannot be prevented. If you are building a new plant or shop floor there are steps that will help to prevent most flooring problems. For existing flooring problems we will discuss how to fix the problems and prevent the problems from getting worse.

Causes of Cracking and Potholes in Shop Floors

Most concrete flooring problems are caused by one of the following:

  1. Improper installation of the concrete, or poor concrete
  2. Improperly cut expansion joints
  3. Steel and hard rubber tires eroding unfilled expansion joints, random cracks and potholes
  4. Chemical attack

Proper installation of Concrete in New Plant and Shop Floors

For new construction make sure you specify and get high quality high strength concrete.  Create a box-out form around beams, pipes and other penetrations that go through your floor. Be sure that the corner of your box-outs line up with the saw-cut joints that you will be putting in the floor.  Penetrations through the concrete cause a "weakened plain". A weakened plane is typically created at the shortest distance between the box-outs.  That is typically from the corner of one boxed out area to the next closest boxed out area.  

Do not allow your concrete finisher to over finish your concrete.  Concrete finishers tend to over-finish concrete because they are concerned that if they don't the owner will not like it.  Over-finished concrete does look better than properly finished concrete until the over finished starts to deteriorate.  The deterioration cause by over finished concrete typically does not take very long to occur.

The best finishing of concrete leaves it flat, but does not bring up the "cream" in the concrete. It will not look as shinny and smooth but concrete that is not over finished will look more attractive and be more functional over time. Bringing up the "cream" in the concrete is done by over working the mix or adding too much water or adding water to the batch. The "cream" consists of dust from the aggregate and Portland cement. 

This "cream" creates a great looking finish at first, because it is so weak, it chips easily.  This "cream" has too high a water content, so you tend to get micro-cracking in the surface. When your concrete finisher is power troweling your concrete and starts splashing water into the surface as he is finishing it he is about to over trowel the concrete and bring up the cream. It is time to get the concrete finisher to stop troweling.

Water curing of the concrete is what most state highway departments require to cure concrete bridge decks. Wet curing is favored over other methods by the US Army Corps of Engineers. Wet curing will help to stop the top of your concrete from drying out too fast. If you cure with a curing compound instead of water, you will need to remove the curing compound to install high quality coatings and sealers. 

Proper curing will help to prevent "curling" of the concrete slab, and help to prevent micro-cracking (crazing) of the surface.  Curling is caused when the top dries and shrinks before the concrete underneath dries and shrink.  This works much like a bimetallic strip used in a thermostat, the concrete will twist upwards or curl.  Proper curing helps to prevent concrete curling and the cracking that will result from it. Another major advantage of wet cured concrete that is not over finished is that there is much less surface preparation required when you go to coat or seal it.

Cut expansion joints often enough, wide enough, and deep enough.  Typically the best way to cut concrete down to 16 foot by 16 foot squares or even smaller.  The larger the spacing between saw cut joints the more likely you are to get a random crack where you do not want it. The concrete should be cut-up as square as possible.  Care should be taken that all the saw cut joints line up with each other in a checkerboard pattern.  Be sure the cut is at least 1/3 of the way through the slab, and that the cracks are 1/4 inch or wider.  That way all the plastic shrinkage (drying) cracking should occur under the saw-cut relief joint.

Using Epoxy to Protect New Plant Shop Floors

Seal or coat the concrete to protect it against wear and chemicals. Product  #223 Water Based Curing Compound, Sealer and Bonding Agent is a two component water based epoxy curing that is used to both cure and seal concrete.

Epoxy Primer and Sealer Product #12 - is a two component, seamless 100% solids epoxy primer system with High Chemical Resistance Epoxy and High Bond Strength.  Epoxy Primer and Sealer Product #12 is an excellent choice for installers that want a high quality long lasting stand alone floor sealer.  Epoxy Primer and Sealer Product #12 may also be applied as a primer for most High End Industrial coatings, like Epoxies, MMA, Polyurethane's, etc.

Allow the concrete to dry for 28 days so that most of the shrinkage at the expansion joint has taken place.  Clean the crack thoroughly, then install a bond breaker "rope" in the bottom of the joint. Then fill the joints with Product #11 Saw-Cut Control Joint Filler- Product #11 Saw-Cut Control Joint Filler is a 100% solids zero (0) VOC, flexible epoxy joint filler for saw-cut joints of concrete slabs on grade, or to repair existing slabs. 

Random cracks and improperly filled expansion joints are where the potholes in plant/shop floors are born.  As steel and hard rubber wheels pass over these unfilled cracks and joints it hammers the edge of the crack in the direction of the travel.  This action cause small chips.  As the process continues small chips become larger chips.  Soon you have a small pot hole and the damage continues to accelerate. 

Product #11 Epoxy Saw-Cut Control Joint Filler absorbs the impact and shock of heavy loads and steel wheeled traffic, preventing erosion of control joint edges. Product #11 prevents the "jack-hammer" effect on the joint that you are traveling towards.  This will help  prevent most if not all of the "pot-hole" effect that most plant floors see developing at their expansion joint over time.

In addition to the Epoxy Primer and Sealer Product #12, you need a moisture tolerant primer  to seal your floor using a 100% solids epoxy use Product #899 - for sealing the concrete. also has a wide variety of shop floor coatings and trowel down systems.  Contact Technical Support Department with your specific needs for a recommendation.

Repairing Random Cracks in Floors with Methyl Methacrylate

Random cracking in plant / shop floors can easily and economically be repaired with Liquid MMA Polymer Crack Repair Resin Product #684LV a penetrating gravity feed crack healer for concrete. It is a two component Methyl Methacrylate resin system that polymerizes in place. The extremely low viscosity will penetrate into concrete cracks as fine as 0.003 inches. Product #684LV welds the crack back together making the concrete as strong as it was before it cracked.

Repairing a Shop / Plant Floor with Epoxy After it is Damaged

For those who have already built their buildings you can still fill all the joints especially in the traffic areas with Product #11 -  Filling the joints with Product #11 will prevent additional potholes from forming in areas where there are none yet.

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To fill the "potholes" in level areas you will typically want Product #10 Lo-Mod Epoxy Adhesive and Mortar Epoxy Binder is a 100% solids epoxy has a low modulus of elasticity (flexibility) and is Low Viscosity. An adhesive used as a binder for epoxy mortar systems in patching and grouting applications, as a seal coat for non-skid surfaces outside, and as a primer to insure high bond strength for coatings and patches.

Product #10 Lo-Mod Epoxy Adhesive and Mortar Epoxy Binder is also excellent for larger projects or surfaces that have a slope so you cannot use a self leveling material should use Product #10 - and Product #82 Mortar Blend Aggregate.  With the right mixing equipment you can put up to 100 pounds of #82 into 1 mixed gallon of Product #11.  That gives you a nice stiff mix, and excellent economy. Product #10 is a low-mod material, with high strength.  That makes it perfectly suited for outdoor patching. Product #10 is the best material for most large jobs.

If the concrete has a lot of pitting in it, you can apply a "scratch-coat".  A "scratch-coat" is done as follows:

1. Carefully measure epoxy resin and hardener. Mix for 3 minutes.

2. Add aggregate to the mixed resin and hardener above, and mix completely.

3. Pour out the epoxy resin hardener and aggregate blend onto the concrete.

4.  Then pull a very tight troweled coat over the entire surface, filling the low spots while scraping as much epoxy resin and aggregate material as possible away from the high spots.

The material for  a "scratch-coat" is with Product #10 - and Product #78 Self-Leveling filler. Product #10 and Product #82 mortar blend aggregate is the best blend for building ramps and smoothing uneven transitions between slabs.

Just because your floor is already damaged by chemicals, doesn't mean it is too late.  Most floors can be saved with proper patching (as discussed above) and a chemical resistant flooring system installed over the patching system. Contact Technical Support for assistance.

Additional Related Reading 

The installation of these materials above are beyond the scope of this page. Here are some areas to explore this in more detail:

Do with Epoxies

Don'ts with Epoxies

Surface Preparation

Chip Flooring Installation Guide

Coating Installation Guide

Coatings Calculator - for roller applications

Links to popular systems used in residential and commercial construction resin work

Air Plane Hangers and Garages

Coating Systems

Outside Decks and Drive Ways

Product Catalog

Bonding Systems


Chips Flooring

Proper mixing and installation is critical to the optimal success of all product.  See Installation Tips, Techdata, & MSDS for more details on our products.  Be sure to contact us with any questions and/or concerns that you have.

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