When making polished concrete, what do you actually do to get the smooth polished/burnished look?

Question

Someone said you have to spend hours working the surface...and then leave it to cure..what does this mean?

Answer 1

Every time you move an object over the surface of fresh concrete you push the aggregate away from the surface and pull the water and cement toward the surface. when you are just trying to get the concrete into its rough shape, near the beginning of the process, you want to use a wooden or magnesium float to try and get the surface as smooth as you can by moving the float back and forth over the surface of the concrete with the leading edge just barely off the surface of the concrete and moderate pressure. If you are applying to much pressure, or you have the float tilted too far you will "flick" the aggregate back onto the surface, if you don't apply enough pressure to the float you will not force enough aggregate away fron the surface to get a burnished finish. If you do not tilt the float at a high enough angle the leading edge will dig into the surface and create a giant gouge. Also, if you want to round over the edges, which is reccomended you will want to use an edger tool during the same time that you are "floating" the concrete. You want to use the float until you have achieved a fairly smooth, uniform finish. Then, wait until the surface water has just evaporated and start smoothing with a finish trowel. Finish trowels are always made of steel, they come in many different sizes, some have rounded ends others have square ends. Rounded trowels are primarily used for curved work, like swimming pools, while square trowels are primarily used for flat work, like walkways. The action with a finish trowel is almost identical to that of a float, but you want to keep the leading edge closer the the surface, and you want to use a lighter touch, just enough pressure to level and smooth the surface. You will need to keep going over the surface of the concrete every 5-10 minutes, until the surface has achieved the look that you are trying to get. It is the consistent use of the finish trowel that helps you obtain a polished, burnished finish. Once the concrete has attained the desired finsh it is time to leave it alone and let it cure. Most people think that concrete "dries" to harden, but it is actually a chemical reaction that takes place in the presence of water that causes the cement to bind all of the pieces of aggregate together. This chemical reaction starts the moment you add water to cement and is about 99% finished after approximately 1 month. For most purposes, concrete has hardened enough after just a few days that it can be put into use. But, for high-strength applications it may need an entire month to cure before it can be used. To aid the chemical reaction and prevent cracking, it is neccesary to keep curing concrete moist. If the concrete dries out too fast it is suseptable to cracking and it won't obtain its maximum strength. Unless the humidity is exceptionally low, or the temperature is incredibly high, there should be enough moisture in the concrete that you can wait over night before you need to wet it down again, if the weather calls for extra water on the same day that you finished your concrete, give the concrete several hours to harden before you spray more water on it, then cover it in plastic sheeting to help hold the moisture in.

Answer 2

Quote: "You can only polish it before it cures. If the concrete is fully hardened then you cant polish it"
WRONG- Concrete can be polished after it is cured. It is becoming a very popular floor finish in commercial construction. Check it out on the web. www.decorativeconcreteofmd.com
You didn't specify if the concrete was cured or not. If so, then you have some good advice by a few of the others. If it is cured it can still be done, with a series of grinding wheels and chemicals.

Answer 3

getting a glass finish on concrete is not hard. i suggest you build a 48" x 48" form out of 2x4's and buy about 10 bags of quickcrete and practice.

you also need an edger, a mag float, and a finish trowel. (go to a hardware store and ask lots of dumb questions too)

put your form on the ground over a sheet of plastic. mix your concrete in a wheelbarrow with a hoe and pour it in the form. when you get the form full, screed it off with a good strait 2x4.

after you get it screeded (it helps to "saw" the screed back and forth while pulling it towards you), wait a few minutes and float the concrete with the mag float.

wash off the wheel barrow and hoe, get a glass of tea and rest for a while sitting in the wheel barrow (sit on the handle end with the handles on the ground, its very comfertable)

after about a half hour float the concrete again and edge it.

keep floating/edging every 20 min of half hour untill you cant take your finger and poke a hole 1/2" deep in your concrete.

when you cant poke a 1/2" deep hole, the concrete has cured enugh to start finishing.

by now you will have figured out how to hold a float so that it doesnt dig in. the finish trowel is about the same. you want a shallow angle, maybe a half or a quarter degree from flat to the slab. the flatter the trowel, the finer the finish will be.

go over you slab every ten minutes with the finish trowel. i use a sweeping counter clockwise arc with my right hand and a sweeping clock wise arc with my left, but that aint neccessacerly the right way to do it.

you will leave little trowell marks the first time, dont worry about it theyll come out the next time you trowel. you just dont want the trowel marks to look like plow furrows made by a drunken flatlander.

keep going over the slab untill its perfectly smooth, like glass.

it may help to have some powdered portland and a hose with a mist head handy.

if you have alot of little "bugholes" and cant work them out, you can GENTLY wet the slab down with a LITTLE water and dust on some portland and keep finishing.

concrete doesnt dry, it cures. concrete will sit for a long time and look like mud, the all of the sudden it will cure very fast. keep this in mind as you go.

when you get done, you will either have a nice little slab that is to slick to walk on, or you will have some thing you can bust up with a sledge hammer and use for back fill.

hope this helps,
possum

Answer 4

Letting in cure, is waiting for it to dry, walking on it too soon will ruin the polishing. We had to rent a power trawl and keep traw ling it this there are no lines from the trawl. (Hope you get a better answer from an experienced concrete person.)

Answer 5

try adding a little bit of nail polish remover, if it's clumpy... or do a clear base coat...also make sure that you use a little as possible by pressing against the opening of the bottle on the way up from getting polish... using three even strokes going from left, middle, to side and a fluid motion helps too...

Answer 6

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This is really something to find that many all together. For someone like me who is just really starting to get involved with woodworking this was like letting me loose in a candy store and telling me I could have anything I wanted. That was my dream when I was a kid.

Answer 7

use a powerfloat its a propeller type base with trowels on with an engine on that arm coming off with handles and rev lever. ive used them for years all depends on the mix summer winter it has different setting times.once you've can walk on it and leave a small indent its ready for first pass over.leave for a while adjust blades you will know when its finishing when it stops leaving lines

Answer 8

You can only polish it before it cures. If the concrete is fully hardened then you cant polish it.

Answer 9

to work the surface get a large brush and dip into the concrete push up and down trying to bring liquid to the top once the liquid is there leave to dry........this is curing........ should leave a nice level smooth surface

Answer 10

you have to wait until the concrete has gone off too trowel (plenty of trowelling) it and wait till it cure (till dry)