Introduction: How to Finish Concrete
Have you ever seen a sidewalk poured with new concrete and watched someone finish the concrete? You probably didn’t pay a lot of attention but you noticed someone down on their hands and knees with a trowel moving around the concrete surface. Like everything else that is done by someone with experience, it looked easy. Guess what? It’s not that easy unless you have done some homework. Sakrete is here to provide you those tips and instructions on how to finish concrete like a pro.
Step 1: Pouring the Concrete
After thoroughly mixing the concrete pour it into the forms slightly overfilling them. Then take a straight board (a 2x4 piece of lumber works great as long as it isn’t bowed) and simply level off the concrete. Using a board that is longer than your pour is wide and using a sawing motion work back and forth until the concrete is level. You really need someone on the other side to help with this part. This is called “screeding” if you are trying to learn new words with which to impress your friends.
Step 2: Smooth the Concrete Surface
If you haven’t done this before or only done it a few times you are likely to make two mistakes; troweling too soon and troweling too much. Both of these have the effect of pulling fines and water to the surface. This can lead to a weakened surface, tiny cracks and a white dusty surface.
Then with a wooden trowel or magnesium float if you want to get fancy, smooth off the surface. This should only take a few minutes. Do not try to turn this into a masterpiece-leave that for art class. This step is simply to put a relatively smooth surface on the concrete. When you are done, go clean your mixer and tools and get something to drink. Keep an eye on the concrete. The first thing you will notice is that some bleed water will come to the surface. This is a good thing. Allow all of the water to disappear before you do anything else. This can take 20 minutes or 4 hours depending on the temperature, humidity and how hard the wind is blowing.
After the bleed water is all gone you can get out your steel finishing trowel and put on the final touches. You will notice the steel trowel is not perfectly flat. That is done so that when you trowel you will be more prone to lift the leading edge slightly avoiding digging into the concrete.
Step 3: Use a Broom to Finish the Surface Texture of the Concrete
Even by following my outstanding instructions it is doubtful that your surface will look a pro did it. As I said in the beginning, using a trowel isn’t all that easy. However, most of us are good with a broom. If your mother brought you up right, you’ve had lots of practice. Once you are finished with the trowel, simply take a soft broom and gently drag it across the surface. Always pull the broom (never push) and always go in the same direction. Just one pass should do the trick. I personally prefer a broom finish because it makes the surface slightly rougher. This is very helpful for those occasions when your sidewalk is wet. A hard troweled surface is very slick. Unless your brother-in-law is a really good lawyer, you don’t want someone take a tumble on your property. Concrete Repair is never fun. Besides this way everyone will think you really knew what you doing and you won’t have to tell them about the broom trick.
Step 4: Cure the Concrete
Don’t stop reading yet or you will miss one very important point. You need to “cure” the concrete. If the concrete isn’t kept moist for a few days it may crack. The problem is that the surface will dry out while the bottom is still wet causing tension which basically tears the concrete apart. There are several ways to cure concrete. The easiest is to simply spray it very lightly with a hose. You can cover it with a wet cloth such as burlap (don’t let the burlap dry out). Or you can use chemical curing agents such as Sakrete Cure `N Seal. The question of how long to do this and how often is a tough one because it depends on temperature, humidity and air flow. The hotter and dryer and windier it is the more you will have to re apply water.
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