Hi everyone.

Odd situation, am wondering if anyone can suggest something.

Originally from England, I moved to Mauritius in 2001 and am now having a house built here. Am interested in acid-stained and polished concrete floors. Hot climate here, so bare concrete floors are very suitable. Back in the day, these would be waxed every few months (only colours available are flat black or flat red), and polished every week or so: not by hand, but by foot (using half-coconuts). Concrete floors have become less common over the last 10-20 years as clients turned towards newly available and affordable ceramic and stone tiles.

My problem is this: nobody on the island knows anything at all about concrete planers or acid-staining. The builder is willing to use any necessary admixtures for the final layer of concrete, and level the floor with hand tools. No machines. After that I am on my own.

1) I would hire a professional to do the work, but there are none; so I am willing to learn and put in the time and effort in this case, although not a DIY enthusiast. Am a maths teacher!
2) The only machines available are single-disc hand-held planers with diameters of 4 or 5 inches. Importing a planetary / walk-behind planer for this is not an option.
3) I am not expecting myself to produce a perfect mirror-like finish on the concrete, just a nice (400-grit?) sheen if possible. I would use a topical sealant too, to make up for that.
4) I am currently searching amazon for books on staining and polishing.

Any feedback (especially on which books if any) would be greatly appreciated. If any of you have ever polished a concrete wall, or the edges of a 3000 sq ft warehouse, then I suppose doing a living-room floor (700 sq ft), or a bedroom (150 sq ft) with a hand-held would not be so much different. As professionals, you usually have a tight time-frame whereas I do not. Are there other advantages of a walk-behind over a hand-held? How many square feet per disc do you usually expect for different grits? I ask because I have not found this information in any manuals. Hope you can help me, without me having to fly a team of specialists over.

So, is this going to be possible, or do I have to settle for the tiles?

Thanks
Ben

ben_nazir@fmail.co.uk

Part of the charm and 'character' of acid stained floors is that they have a certain level of rustic'ness. Which is to say NOT polished, or otherwise not finished to the level you are thinking.

In Colorado Mountain towns, like Aspen and Telluride .. it can be downright dreadful as "nouveau skanky" architecture" is the hottest chicest, most fabulous thing. Wherein the newest building in town looks like a mine shack that should have been torn down 100 years ago. SO.... if it ends up looking too rustic and nasty, just tell people you did it in the "nouveau skanky" style, like they Mountain town millionaires.

A good hard trowel surface is a good place to start. After that it is common to sand the floor with a buffer/ floor machine. (Being an Army veteran I call the machine a buffer) Basically they have giant sanding discs the size of a super large pizza. 30, 60 and 120 grit. Hopefully one of these type machines is available, it is the most basic janitorial tool aside from the mop & broom. NOT TOO be confused with a BURNISHER.

To take down any trowel burning, ridges etc.. and to make marks & stains disappear (penciled crows feet, chalk line etc) there is the "nuclear option". Diamond hand pads. 50, 120 and 250 maybe 500 grit. It removes a thin layer of cream surface and the stain/mark with it...Stop sanding when you see aggregate. OR to "antique" certain areas, make it look more worn. Diamond hand pads are the most useful tool to have when prepping for acid stain. IMHO they should be sold wherever acid stain is sold, why this is not so is beyond my comprehension.

Fu Tung Chengs book "concrete at home" is highly recommended reading. Also check the Portland Cement Association bookstore. There is also good info at their website. All the science and whatnot can be found there.

IF by any chance this will be with site mixed concrete.. Mix design will be an issue. IT is preferred to do decorative concrete with a designed mix. A shovel of this, that and the other is no way to design a mix. Mixcalc software is what I use.

A 6 sack mix is in the range of what you want. The rule of 6's for concrete. 6 sack, 6% air and 6 days of moist curing. You cant go wrong with the concrete beast when you follow the rules of 6.

Also in your mix should be Microfiber, the cat hair sized stuff NOT the cat whisker sized stuff. All concrete poured in this day and age should have fiber. It results in a better matrix, and it does help against shrinkage cracking.

An alternative to acid staining is Smith PAints Water based acrylic. Color Floor is the one you are looking for. Real colors (not just sh**e'tone brown), acrylic water based, no acid ruining your clothes, and that dreadful taste in your mouth, or the dusty& rusty smell the next day either. If I recall it is about the same $50 per gallon as acid stain, but you get twice as much because you dilute it with pure water. Sample sized bottles are like $5.

Hey. Thanks for the reply and advice.

I added the Fu-Tung Cheng book to an existing order on amazon; should have it by late December.

[ [ A shovel of this, that and the other ] ]

That is how builders often work here, and that is what clients often accept, especially as regards finishing and aesthetics. I will do some research at the PCA website especially on admixtures because the concrete will indeed be mixed on site and the final layer will be designed specifically to be stained and polished. If I decide to do this.

Meanwhile:

I think I would prefer stains to dyes. I love the random variagated tones which I have seen, but (depending on things) I would still like some surfaces to be as polished and smooth as possible. I have not seen a buffing machine here yet.

So what about the hand-held grinder / planer; do you have much experience with that? The hand pads you mentioned sound interesting. Can this really be done by hand? Say you had already used a 50-grit pad and were now going to use a 120-grit pad. How many square feet would you expect out of a pad, and how long would it take?

Thanks again

Ben

The hand pads are more for touch up, especially getting odd marks and stains out. Just remember its not a stain remover so much as a concrete remover. Hence why I call it the "nuclear option" for stains.

A grinder with diamond pads is not outside the realm of possibility, its just a lot of work to do a whole floor that way.
You realize of course, its going to produce a terrazzo look exposing the aggregate? Any way you grind and polish will do this BTW. The floor machine/buffer with giant sanding disc wont remove as much cream surface, but it will smooth things out.

[ [ produce a terrazzo look ] ] - Yes that’s ok but the final layer of concrete would not contain large aggregate, only fine sand I think. Am assuming that about a quarter- or half- inch of this concrete would be removed in total during grinding and polishing. OK let us take another angle: if a concrete surface is sanded with progressively finer grits, at what point will it become droplet-forming / noticably slow to absorb / waterproof, any ideas?

Barely 1/64" gets you into the cream surface, exposing aggregate whatever it may be. Sand of course will the the first agg. showing in any mix. 1/16" is quite a lot too. 1/4" to 1/2" is way deeper than you will be going.

Part of the picture here is mix design. The only way to be able to get that smooth, down to water beading smooth... is if the concrete is even capable of that. Higher psi, higher density is the only way. I am guesstimating 6.5 sack + pozzalone of some sort.

Pozzalone or supplemental cementitous material, are typically finer particles than Portland cement often in the 300 mesh range. Fly ash, koalin, silica fume, silica flour, diatamacuous earth etc. Any silica dioxide product. (Portland cement is a pozzalone also, it happens to be the most active one, hence its usage in concrete.) More fine particles filling more small spaces. You also get a chemical reaction, better crystalline structure and overall better matrix. For statuary, I calculate pozzalone (I use PowerPozz) as an addition.

Also when it comes to filling every possible small space with particles..... an Air Detrainer admix might be useful. It can take your ideal air content of 6% down to as little as 1%. The less space that is taken by air, the less the concrete will look like a sponge. http://www.cementdepot.net has fritzpack "air minus" detrainer.

http://www.pensacolatesting.com/mix/index.html I use mixcalc 102. I like to be exact with my mix, rather than guessing with the 1 - 2- 3/4 recipe.

Concrete might be deceptive too, with that water beading. For the first 14 days especially, regardless of density/ smoothness.. concrete is thirsty. It actually makes a particular sound when you "give it a drink". I know how cured concrete is by the sound.

OK thanks again, especially for the numbers.

Yesterday I did actually find a contractor who does terrazzo; it was interesting to see, and the price was lower than I expected, but it seemed very basic and his samples (even his own house flooring) were not well thought-out or well-polished. So I am still considering doing this myself.

Kaolin / metakaolin and silica fume are white, no? So that is interesting. I read about fly ash also at the PCA website. Do you know are these additions/supplements affected by acid-staining?

If I recall, there really wasn't much in the way of proper/ideal polishing equipment in your area. That being the case.. it is no particular surprise that the terrazzo guy had less than perfect examples.

Some forms of silica dioxide are grey, dark grey such as fly ash.

Koalin/metakoalin, the stuff i use "powerpozz" from http://www.concretedepot.net, is an oyster off white.

Cabosil silica fume (from fiberglass supply places) is stark white, and an altogether unusual substance. Very dangerous, as far as breathing it in. The specific gravity is like 0.18 or something like that. The stuff will gel water, or acid for that mater. I have used it before in a few mixes. The problem you might have with acid staining, is that concrete with a healthy dose of this stuff seemed to be more resistant to acid than I would have liked.

OF course, that is one of the good things about pozzalone.. a better matrix, smaller pores, more impervious to everything. You might very well realize a less intense reaction to the acid. Which might be annoying whillst staining.. but it tells you that your concrete is a better grade and density than the stuff they mix for sidewalks.

Acid staining is a reaction with one of the chemicals, in the mad scientist mix we call concrete. I cant remember which one offhand, but it may have been lime or some hydroxide or another.

P.S. an excellent terrazzo effect... ALL GLASS aggregate. This mix had some bits of larger glass green and red, and smaller glass is post consumer (beer, wine, plate glass etc) I had a perfect gradation from 3/8 all the way down to dust. Cabosil silica fume, and ceramic microspheres for pozzalone. This pics are in a rough state, and really dont do the samples justice.

The cool thing is.. drum roll.. a "feel illusion" everywhere you touch is as smooth as polished glass, because you are touching rather a lot of polished glass. Big points for green building, granola crunching, and recycling!

All Glass agg concrete sample

All Glass agg sample

I am almost certain that you have a pile of glass somewhere in your area. They might not have a clue what to do with it, which gets you ideal pricing. Handling it then becomes the only issue.

I will PM you later with a couple of mixes, when I run some numbers through my mix calculator.

The white spots.... I was very careful with water on this, and it went sloppy wet looking fast. Not knowing at the time that it was merely the effect of very little friction, much like adding plasticizer... so as a last minute thing to stiffen it up a bit I added some more white portland. That bit of white portland, did not thouroughly mix but rather only got to the "dingle ball"
stage. An interesting effect, that I might do on purpose someday.

I may not have mentioned it before.. A warning about exposing too much aggregate for an acid stained floor..

About 10 - 15% of the mix is cement. About is 5 - 7% water. 6% Air, and the remaining approx 75% is aggregate. 40% of that is sand, and 60% is gravel.

The air will not noticeably react or stain at all. The aggregate, about 75% of your floor will at best get a residual stain, that is to say fine particles and residue rather than a reactive stain. Most of this will be removable with a broom and damp mop. The part that will react with the acid stain, comprises only 20% or thereabouts.

Again, I am saying the acid stain may not be as intense, or noticable on a polished highly exposed floor. This may be an effect that you like. By an large however, the prevailing preference is for a "rougher" floor (less polished and exposed) , with more cream surface.

Doing some test panels/ tile sized samples and experimenting first might be in order. Just make sure and document what you did to each one so the particulars can be referenced later.

** I might also recommend posting a separate topic regarding densifying sealer (I believe its a Euclid product). This might get you to the polished look without so much of the physical/ mechanical grinding. Also a top coat over the sealer with some of the higher tech polymer waxes, and a good military grade buffing/ burnishing.

Sounds like a good business venture, eh? If you do well, you can teach laborers your techniques and hire them to offer this service to other residents.

Good luck!

Tasha Lucas
http://www.monsterconstructors.com