Exposed Concrete Aggregaate Slab – At least that was what it was supposed to be. Dued to many errors, the surface set up before the process to expose the aggregrate could be accomplished.
What, if anything can be done to create an exposed aggregate?
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Replies
I would have immediately ran out and picked up my 3000 psi pressure washer, that should do it within a few hours, other than that, maybe muriatic acid?
Darren
http://www.LDHindustries.com
You can sandblast it. Perhaps a well-equipped rental yard can supply the gear and the blasting medium. Do a web search on exposed aggregate techniques and you will see some stuff on sandblasting.
You have to be very skilled with a sandblaster to have a consistent finish and very few can do it.
You could rent a floor grinder and with relative ease expose all the stone.
Gabe
I was watching a contractor the other day doing some exposed aggregate work. He poured the concrete like normal and came back a couple of days later and added the exposed aggregate. It was very fine aggregate though, and it was on a conc. wall. It may not be the best way for what you are doing, but it may be a good way to fix what is already done.
I've seen that before, an overlay of aggregate, there is a brand thats been around forever called Stone Coat, you could search for that possibly.
For future reference, if you spray some retarder on the surface of the concrete after it's poured, you pretty much can't screw it up as you have hours and hours afterwards to come back and expose it.Darren
http://www.LDHindustries.com
Kyle,
Some sort of solution was used, which I had never used myself. The first problem was the boss was having someone use just a little garden variety sprayer.
I will check out the Stone Coat.
Thanks to all who have replied so far. I didn't want to share a long story of all the mess-ups in this pour, however, the main problem was the bosses continued statement of we'll get back to that. Also, it took over three hours to place just over six yards of concrete on a totally level surface and the temp was in the 80's. I did have the boss get the pressure washer, which did remove some of the fines, however, my final suggestion was to get a jack-hammer and start over. He didn't like that. The grinder sounds like a good fix, however, the home owner does not want a flat surface.
I am wondering if anyone has had experience using muratic acid? How strong a solution for a problem like this? Also, is there any concern about the acid soating into the concrete below and causing future problem?
Thanks again. Nice to hear others ideas.
I have exposed aggregate driveway, front walk, and back patio, and I wish it was smooth. Dirt doesn't wash out easily, so the slab gets dark quickly. Also, it can be a little uncomfortable in bare feet. Gabe's idea will result in a form of terrazzo, which could look very good with a clear sealer.
Do it right, or do it twice.
The problem with the muratic mix required to disolve the cement will also loosen the stones.
BTW there's no such thing as an effective sprayed on retardent after the concrete is placed when trying to have an exposed concrete finish.
Gabe
BTW there's no such thing as an effective sprayed on retardent after the concrete is placed when trying to have an exposed concrete finish.
You are not very smart. I previously thought you might actually have some sort of knowledge but you've once again proven us wrong. I'm betting you have never placed one square foot of exposed aggregate yourself.
Darren
http://www.LDHindustries.com
Edited 11/2/2003 4:18:58 PM ET by SledBC
Ya, you're absolutely right. I don't know a damn thing about concrete compared to you. You're the master.
That's why I attended the Sens game last night as a guest of Lafarge in their corporate suite so that I could be as smart as you.
DF
Gabe
BTW made a fool out of you regarding vb, want to try 2 for 2?
BTW made a fool out of you regarding vb, want to try 2 for 2?
You have to be kidding me, you provide a link to a page that was irrelevant to your argument, I proved YOU wrong, you dodged the issue and refused to answer my questions to you because you know it would make you look the fool that you are. If you tell anyone that you won that argument you are a liar, you chickened out....and by so doing, I win. In fact that puts me up one if you want to be a stickler. If you want to win, go back, answer my questions, I'll gladly continue that argument.
The fact that you would tell this guy that there is no effective way to use retarder when exposing concrete proves you know nothing. I could care less if you buy lots of concrete from Lafarge, that doesn't mean you know anything about it. Using retarder is a sure way to ensure consistent results when doing large pours or in inconsistent weather conditions. I'm still sticking to believing you have never personally exposed concrete.
Darren
http://www.LDHindustries.com
Edited 11/2/2003 10:36:56 PM ET by SledBC
Before I send you back to the pencil box to be resharpened again I will explain for the benefit of others seeing that you'll never get it.
A few post back I wrote a comment about set retarders not being that good for exposed aggregate finishing and as usual SledBC jumped on it with both feet.
Surface retarders are sometimes used by contractors to allow time to do exposed aggregate finishes with complex patterns using different colored stones.
Set retarders do not prevent the concrete from hardening, they just retard the setting time with active chemicals over a pre-determined period. Different grades of retarders result in different depths of etching. They can be either solvent based or water based. There are different viscosities for different applications and conditions.
Experimentation is required with sample batches in order to select the right retarder to produce a specific effect.
To properly use a surface retarders is a trick in itself. Absolute consistency is important. If you don't vibrate evenly, different batch temperature, if you have ponding or if you have inconsistent batches you will have a blotchy final finish as someone already described as camo like in appearance.
Set retarders are not a quick fix for bad timing or trying to do too large of a slab at a time.
The wrong retarder having an adverse chemical effect on a batch of concrete which can have a negative impact on final concrete strenght results.
Therefore I stand by my opinion that set retarders shouldn't be used by people with limited experience to compensate doing too large a project at a time.
It is highly recommended that if you only do the odd exposed aggregate finish project or just one in a lifetime that you do it in smaller sections and stay away from chemical quick fixes.
One last thing............don't take advice from SledBC, he failed sandbox and never recovered.
Gabe
BTW there's no such thing as an effective sprayed on retardent after the concrete is placed when trying to have an exposed concrete finish.
<snip>
Set retarders are not a quick fix for bad timing or trying to do too large of a slab at a time.
The wrong retarder having an adverse chemical effect on a batch of concrete which can have a negative impact on final concrete strenght results.
Therefore I stand by my opinion that set retarders shouldn't be used by people with limited experience to compensate doing too large a project at a time.
I don't want any part of whatever you and Sled have going on. I would, however, like to understand this. After your first posting I searched and found a lot of retarders offered. My one experience, without a retarder, with a 12 yd pour went very well. The only reason I didn't use a retarder, as advised by my concrete supplier, was financial. I was barely able to pay for the concrete as it was my last pour before moving in.
You're saying that retarders are effective if you know what you're doing but otherwise a bad idea? I no longer remember what product was pushed at me but I don't see why a reasonably uniform application would be difficult. Clearly the concrete would vary a lot at the time it was sprayed, especially as I can only get 6 yds at a time. I don't have as uniform a surface as some I've seen. We prefer ours but I've been assuming that my not using a retarder was the reason. No? PAHS Designer/Builder- Bury it!
Tom,
A 12 yd pour is reasonable to handle as long as you're prepared and obviously you were.
Any flaws you may have would be the result of not having enough practice and not due to not using a retarder.
Remember this, concrete companies make more profit selling admixtures than they do selling plain concrete.
Gabe
I am the guy that suggested the sand blasting. I have a really good looking exposed aggregate slab at the entryway to my house. I used a molasses-water mixture applied with a garden sprayer to the well-floated slab, after we had salted the top with multicolored river gravel. At the same time as we did the slab, we poured three little 12"x12" pads formed with scrap 2x4s to use as testers for determining the best wash-off time. I babysat the slab, used the sprayer first on a little test pad, and decided after the second one, that it was right for a wash-off. Beautiful!
You might try the same with a sand blaster. Three or four little test pads. Use the blaster on them before tackling the one that sat too long to use the wash-off method.
VaTom, it is far easier to get a consistent finish if using a retarder sprayed on the surface after floating. We usually buy a water based retarder from the concrete company, my last pour the cost was minimal, if I remember, around $50 for the retarder. It turned out perfect, absolutely consistent, which would be difficult otherwise in that situation as the driveway had a 15% grade and some areas were in the sun while others weren't. We were able to completely place the concrete, go for lunch, return, get organized and then expose the entire area. Without retarder it would have been virtually impossible. If I'm doing a small job, the other day I poured a 10x4 sidewalk, and of course didn't use retarder, but on larger jobs I wouldn't consider without.
As far as Gabe is concerned, don't worry about him he likes to ramble on and contradict others for the fun of it. The only reason he posted here was to attack my original reply. If you read all of his posts you can see how many times he contradicts himself.
I still think he has never personally exposed any concrete, so listening to him would be no better than calling up Bob Vila. I only reply to try and help others out with my experience just as I appreciate the sincere help others give to me when I need it as well. In the end I want my customers to be happy with the finished product and give just a little more than the competition.
Darren
http://www.LDHindustries.com
Edited 11/3/2003 8:31:33 PM ET by SledBC
Post 1 by Gabe:
There's no such thing as an effective sprayed on retardent after the concrete is placed when trying to have an exposed concrete finish.
Post 2 by Gabe:
Surface retarders are sometimes used by contractors to allow time to do exposed aggregate finishes with complex patterns using different colored stones.
So which is it Gabe? most of your posts are full of completely irrelevant babbling, and in the midst of it you contradict yourself. These "contractors" you speak of obviously know more about exposed aggegate than you do. Why don't you try to actually help this guy out? Your first answer is dead wrong, admit it.Darren
http://www.LDHindustries.com
Pay attention SledDF
Post 1. I don't like them and I don't recommend them for people who only do the odd slab. It is my professional opinion. If you knew anything about concrete you would know that no two batches are perfectly identical. Concrete varies from plant to plant, town to town, state/prov. to state/prov., country to country. The same retarder will work differently in each case so only an idiot would blindly recommend them to unknown situations.
Post 2. Some contractors do use them but with mixed results. Just look at the garbage you have done.
Gabe
The same retarder will work differently in each case so only an idiot would blindly recommend them to unknown situations.
EVERY concrete job is different from the last, that is a given. With every task there is a better way to do things, this is what I recommend. You argue with it, you are a fool.
Have you ever placed and exposed any concrete with your own hands Gabe?
Darren
http://www.LDHindustries.com
Edited 11/3/2003 10:05:45 PM ET by SledBC
I hate to disapoint you but I've done just about every finish available today with my own little hands. I've used just about every piece of finishing, grinding, chipping and sandblasting equipment on the market.
I'm not just an ugly face. I came up through the ranks and enjoy life at the top.
Up yours
Gabe
I have had experience with muriatic acid, though not doing what you need to do. I've used it to clean both new and old stone and brick work. I really don't have a sense of how much material you have to remove, but muriatic doesn't move that much that easily. And, its pretty miserable stuff to work with in my view. When I use it I always wear a full face respirator with organic vapor filters, and I wear rubber and/or rain gear from head to toe. It does indeed "fizz" like crazy on the concrete and does loosen surface material, but...
Bob,
Forget about the muriatic acid helping to solve this problem. I've worked concrete before and the only time we used muriatic acid on exposed aggregate was when we had poured a commercial job with tilt panel walls. The aggregate that arrived on the job site was smaller in diameter than had been specified, it was nice in color, but so small as to cause problems in the finishing process. Basically we had to go "extra" light on exposing the stones because if we got just the little bit to aggressive we would completely remove the exposed stone aggregate.
We had no choice but to use the small aggregate because it showed up just minutes before about a dozen loads of hot concrete showed up. The supplier agreed to a back charge to cover the cost of one man "me", spending two weeks with diluted muriatic acid and a rubbing stone trying to get a little more of the stone to show without "burning" or "staining" the stone I was exposing. This was done starting just one day after the poor. Even being a good "patch" man the job still came out looking a little like a "camouflaged" WWII bunker in North Africa. Not exactly the look our costumer the
GC was trying to sell to his client.
If the stone being used for the "exposed" aggregate is not even showing I would agree with others and say you will save yourself a lot of grief by adding another layer to get the look you are looking for.
P.S. I hope you haven't paid the clown who did this to you. IMHO I think the contractor responsible for this SNAFU should foot the bill to make it right.
Wishing you lots of luck with a nasty problem.
Cork in Chicago
(I'm an entirely different "Bob" than the one who posted. Who would have thought there could be more than one Bob in the construction business? Oh, well.)
I don't have the same problem, but not being a concrete expert maybe you can answer a question or three. If I wanted to add an exposed agregate surface on top of an existing small slab, what do I do? Skim coat of mortar, spread aggregate, bed it and then brush and wash? An inch or two for the skim coat is too thin for concrete, right? Any special bonding agent necessary? Will this work on old or fully cured concrete? I have not decided I actually need to do this yet, just trying to figure if it is an option.
Bob,
I don't have a good answer for you but I do have some info.
A while back BT had a long thread on this subject and there was some great info that was posted here from the web. If you do a search for it here or if you just do a Google under "exposed aggregate" you'll find lots of expert info from people in the industry. As I recall the info was easy to find and specifically addressed the issues you raised.
Though I had done this type of work about 25 years ago it was real interesting to see all the different ways to go about doing this type of work. Reading this info was a real eye opener.
You should have an easy time doing this search and quickly find scads of in depth, easy to understand info that will clue you in and give you a feel for how to go about figuring out and planning any possible project of this nature.
Good Luck-Go do your Google,
Cork in Chicago
> ....What, if anything can be done to create an exposed aggregate?
I wouldn't even go near any attempt to expose the aggregate with acid! You're trying to remove far too much matrix to get to the aggregate, in my opinion. No, I'm not a concrete contractor, and no, I've not poured acres of exposed aggregate. But I *have* worked with muriatic acid to clean tile and stone and like others have testified, it's not nice stuff. It's designed, again, in my opinion, to remove a thin film of cementious material. Not up to an 1/8" or more.
What sort of slab are we talking about? Patio; porch;.... Would an additional lift of concrete cause grade problems? If you can afford a new 4" lift of concrete over the botched job, this is the easiest fix I could see without knowing more about the project. 3" absolute minimum. Along with some mesh in it to control cracking. By the time you get round to settling the issue, the first slab will have had time to cure out some, I suspect, so you may have to contend with shrinkage in the new slab compromising a bond between the two.
The proper fix, from an architect's point of view, would be to remove the bogus work and have it done right.
Yes, I am an architect. But please don't hold that against me! (grin)
Dennis in Bellevue WA
[email protected]
Go to the Mapei site or contact your local Mapei representative. Depending on local site conditions, one of their concrete toppings with added aggregate may just be the ticket for your problem.
Gabe