Do you have wide and unsightly cracks in your concrete sidewalk, driveway or patio? The concrete may have been cracking throughout the entire floor, and one piece is now taller than the adjacent one—possibly causing a trip hazard.
Every Sunday, I walk up the disabled ramp of the church, where some handymen, contractors, or well-meaning volunteers shake their heads as they try to repair similar cracks. They failed miserably, and many of my older fellow church members were in danger. Hump maintenance is breaking down, and this is an accident waiting to happen.
Let us first discuss what to do if you have cracks and the concrete blocks are on the same plane and there is no vertical offset. This is the simplest of all repairs, and you are likely to complete the repair yourself in an hour or less.
I will use the tried-and-tested concrete epoxy resin for the repair. Years ago, it was difficult to put epoxy resin in cracks. You have to mix two thick components together, and then try to carefully put them in the cracks without making a mess.
Now, you can buy the stunning gray concrete epoxy in ordinary caulking pipes. A special mixing nozzle is screwed on the end of the tube. When you squeeze the handle of the caulking gun, two epoxy resin components will be sprayed into the nozzle. A special insert in the nozzle mixes the two ingredients together so that when they move down the nozzle about 6 inches, they are completely mixed. It couldn’t be easier!
I have successfully used this epoxy resin. I have a concrete epoxy repair video on AsktheBuilder.com that shows how to use it and how the nozzle works. The epoxy resin cures to a medium gray color. If your concrete is older and you see individual sand particles on the surface, you can camouflage the epoxy by gently tamping sand of the same size and color into fresh epoxy glue. With a little practice, you can cover up the cracks brilliantly.
It is important to understand that epoxy resin needs to be at least 1 inch deep into the crack. For this, you almost always need to widen the crack. I found that a simple 4-inch grinder with dry diamond cutting wheels is the perfect tool. Wear goggles and respirators to avoid inhalation of concrete dust.
Make the crack 3/8 inch wide and at least 1 inch deep to get good results. For best results, grind as deeply as possible. If you can do this, two inches would be ideal. Brush off all loose materials and remove all dust, so that the epoxy resin forms a strong bond with the two pieces of concrete.
If your concrete cracks are offset, and one part of one of the slabs is higher than the other part, you need to cut off some of the raised concrete. Once again, the 4-inch grinder with diamond blades is your friend. You may need to grind a line about 2 inches away from the crack so that your repair work is as smooth as possible. Due to the offset, it will not be on the same plane, but you can definitely get rid of the danger of tripping.
The thread you grind should be at least 3/4 inch deep. You may find it easier to create several parallel grinding lines about 1/2 inch apart to travel towards the original crack. These multiple lines allow you to hammer higher concrete with a hand chisel and a 4-pound hammer. You can do this quickly with an electric hammer drill equipped with a cutting tip.
The goal is to create a shallow trench where you will place cement plaster to replace the elevated concrete. Grooves as shallow as 1/2 inch can also be used, but 3/4 inch is better. Remove all loose material again and remove all dust on the old concrete.
You need to mix some cement paint and cement plaster mixture. Cement paint is just a mixture of pure Portland cement and clear water. Mix it to the consistency of thin gravy. Put this paint in the sun and mix it only before you plan to use it.
Cement plaster needs to be mixed with coarse sand, Portland cement and slaked lime, if possible. For a strong repair, mix 4 parts sand with 2 parts Portland cement. If you can get lime, then mix 4 parts sand, 1.5 parts Portland cement, and 0.5 parts lime. You mix all these together and dry until the mixture has the same uniform color. Then add clean water and mix until it becomes the consistency of applesauce.
The first step is to spray some concrete epoxy into the crack between the two boards. If you must widen the crack, use a grinder. Once you spray the epoxy, immediately spray the grooves with a little bit of water. Let the concrete damp and don’t drip. Apply a thin layer of cement paint on the bottom and sides of the shallow trench. Immediately cover the cement paint with the cement plaster mixture.
Within a few minutes, the plaster will harden. You can use a piece of wood to make a circular motion to smooth the plaster. Once it hardens in about two hours, cover it with plastic for three days and keep the new plaster moist for the entire time.
Post time: Sep-07-2021