There is something very attractive about a smooth, shiny surface, so it’s no surprise that a lot of people want their concrete to display these qualities. After all, if you’ve gone to all the effort to lay down a piece of concrete, it only seems right to make sure you get the look that you want.
To achieve a smooth and shiny concrete finish first requires proper leveling, floating, and troweling before it cures. After attaining a relatively smooth concrete surface, and once the concrete is dry, you can utilize either mechanical or chemical polishing methods to achieve a nice, glossy shine.
There are right and wrong ways in which to go about creating the perfect finish for your concrete, and it’s essential to know the types of tools and methods that are available to you. We’ve divided the process into what to do before curing and what to do after curing.
Why the Finish Matters
Your finish affects the texture and durability of your concrete. How you choose to finish your concrete is entirely up to you, but it will largely depend on the location of the slab and what your intended use for it is (source).
Exterior concrete usually requires some texture to make it slip-resistant, while interior concrete needs to be durable but also flat and smooth. If you plan on covering your concrete with a floor cover, like a carpet, then it’s not as imperative that you have a perfectly smooth finish.
There are several different types of concrete finishes that you can achieve, depending on your desired look and functionality. Some of the more common finishes include (source):
- Trowel Finish
- Broom Finish
- Stamped Concrete Finish
- Salt Finish
- Polished Finished
- Colored Finish
For smooth and shiny concrete, you are going to employ both the troweling process as well as the polishing process to achieve the finish that you desire. The final polishing process involves a specialized polishing machine that utilizes a penetrating chemical and/or abrasives.
Before Curing: How to Achieve the Smoothest Concrete
When finishing concrete, there are several things that you have to do to get the desired results no matter what type of finish you want.
If you are looking for the smoothest finish possible, then you need to follow specific steps (source).
Step 1: Level the Concrete
Once you’ve laid your concrete, you need to level it. Two commonly-used tools for leveling fresh-laid concrete include the screed board and the darby.
The screed can be a strip of aluminum or merely a flat board that you draw over the wet concrete. A darby is essentially a large trowel with a long, narrow strip and one or two handles to cover a wide area.
The first thing is to level your concrete by taking your screed board and pushing it across the surface of the concrete. The screed will help fill any gaps in the surface and also remove any excess concrete. Afterward, you can employ your darby to smooth out the concrete further.
It’s best to move the darby in an arc-like pattern and keep it level so you don’t leave any imperfections on the surface.
You should do this before the free water from the concrete mix, known as “bleed water,” rises to the surface of the concrete (source).
Step 2: Wait for the Water to Bleed Off
You should now wait for the excess water to rise to the top of the concrete before you move on to the next step in smoothing out the concrete. The bleed water will evaporate on its own, but how long it takes will depend on the qualities of the concrete as well as environmental conditions.
It’s essential to wait for the bleed water to evaporate fully; otherwise, you risk running into problems like dusting, scaling, and delamination in the future.
Step 3: Float the Concrete
Floating concrete is a critical step to achieve a smooth surface. While using a screed and darby gives you a roughly smooth surface, floating helps smooth out further imperfections, compact the concrete, and prepare for additional finishing steps. You can float concrete by hand or by using a machine.
When floating concrete by hand, you can use small hand floats or larger bull floats. While a simple magnesium hand float will work fine for smaller surfaces, you may want to use a bull float for larger surfaces to ensure the aggregates settle properly.
A bull float has a long handle that allows you to push or pull it across the concrete surface. A bull float usually is 10 inches in width and up to 10 feet in length.
The mechanical floating method is increasingly popular, but the concrete has to be firmer before you can attempt it. These machines have large, flat floats made out of metal that smooth out the concrete, leaving very light circular marks (source).
To ensure that the concrete is dry enough to hold the weight of the machine, you can press into the concrete with your shoe. If the imprint is less than 3mm deep, it should be safe to machine float.
Step 4: Trowel the Concrete
Troweling is very important for indoor concrete. In this case, you’re using a float trowel, finishing trowel, or flooring trowel.
The method for achieving a very smooth surface is to trowel repeatedly in consecutive sweeps using a steel trowel and increasing the pressure as you go along (source).
Be careful that you don’t tilt the trowel as you go along, or you’ll create a “chatter” texture, which will not give you a smooth surface. Also, remember never to add any water to your concrete while finishing it.
Edging and Jointing
Two additional steps worth mentioning when it comes to finishing concrete are edging and jointing.
Edging involves using a small hand trowel along the edges of your concrete slab and helps to give you a neat, clean edge around the perimeter.
Joints are used in concrete at specific intervals to help reduce cracking as the concrete expands and contracts during changes in temperature (source).
Jointing often involves using a concrete jointer tool that has a blade that is ¼ of the depth of the slab. Alternatively, you could use a spacer of some kind as a guide to cut grooves into the slab.
Step 5: Allow the Concrete to Cure
Once you have completed all your finishing steps, you can now allow the concrete to cure. Once it has completely cured, you can move on to the polishing process.
After Drying: How to Achieve the Shiniest Concrete
Achieving a nice shine on a piece of concrete does not come from a single product or sealer, but instead by having it polished and polished well. In most cases, a mechanical polish can achieve the shiniest surface with the least amount of effort (source).
Diamond polishing is a method now readily available to the general public, and it is employed in public spaces everywhere.
You can see diamond-polished floors in malls, airports, and the like. It is now the most popular way to achieve a gleaming surface as a method that has both the benefits of long life and low-maintenance costs (source).
Diamond polishing is a mechanical process that employs industrial diamonds to smooth, grind, and polish surfaces (source).
A mechanical polish relies on the actual concrete for a reflective finish instead of a sealant, guaranteeing long-lasting shine.
Polishing concrete involves up to nine different steps using a variety of different grinding tools. There are also different levels that you can achieve, depending on how shiny you wish your surface to be.
The finer abrasives come in 800, 1500, and 3000 grit, depending on the desired sheen that you wish to achieve. The higher grit you get, the finer the finish will be.
Polishing floors by mechanical means is considered highly sustainable, durable, and doesn’t require harmful chemicals or solvents. The good news is that this method of polishing can be used to spruce up old concrete as well as on new surfaces.
So if you are looking for a long-lasting, sustainable shine, then a mechanical polish is certainly the way to go.
WARNING: Something to consider on smooth shiny garage floors!
Should You Make Your Garage Floor Smooth and Shiny?
Back in the day, I had an old Finnish man pour and finish a new detached garage floor for me. He spent all night troweling the concrete with his power trowel spraying water and making the final floor shiny and smooth. It sure looked nice but should you make your garage floor shiny and smooth?
No, you shouldn’t make your concrete garage floor shiny and smooth, it does not hold up to chemicals and salt especially in northern climates. It is also dangerous and slippery when you have water, ice, or snow on your feet or from your vehicle. Shiny smooth concrete may look nice but it is not the best for garage concrete floors.
There are exceptions to every rule but we live in a northern climate and found out all too fast how much we disliked our new shiny garage floor especially once winter set in. It was just too slippery when it got wet and full of snow.
To achieve a smooth and shiny surface, you need to pay careful attention to the finish of your concrete. This means making sure that you float and trowel your concrete correctly and also give it a good mechanical polish.
If you follow all of these steps, there is no reason that you won’t be left with a concrete surface that is both smooth and shiny.