Dusting floor

[Jeeper89]

Well after a long battle with the concrete contractor my floor has been in for about six weeks now. Some of you may have seen some of my posts a while back but to get you up to speed. 40x60 barn floor 4" think with a few thicker pads for a future lift. The pour was done on May 11th, a rainy wet cold day (53 deg by memory). I had them put plastic under the slab just to help keep any moisture out. I also had stated that I wanted wire reinforcement used. Long story but at the last minute he switched from wire to residential fiber without my approval. I'm still not 100% sure that was actually added but he did provide me with a load slip showing it was added. Anyway due to the cooler weather, the high humidity, and the plastic under the floor the cure time was really slow and all of the water came up to the top. They started the pour Friday morning about 10:00. at 9 PM they did what looked to me a very wet first pass hand trowel. He left saying he would be back at 2:30 am to do another pass. 7:30 am I go out there and no one has been there. He shows up at 8:20 with a brand new power trowel. (The main concrete supply house if about 20-25 min away and they open at 8am hmmm) anyway he starts the trowel up and after attaching the clutch cable goes to work. I had to leave for work. I get home later that afternoon to a floor I am less than impressed with. We argue over text messages he calls it a 10 I call it maybe a 6. I chalk it up to getting screwed and face the fact I am going to have to live with it. Well here I am six weeks later and when I sweep the floor I keep getting gray dust and the "smooth" floor finish turns into dust. Leaving me with a 80 grit sandpaper feel. What can I do to help slow this down? The barn will be used for parking my truck in everyday, storing my pontoon and camper and the back 20X40 will be a hobby shop with wood working and welding going on at times. I need something that won't break the bank because at this point I am way way over budget and I don't have much cash left to spend. I have been looking at Ghost Shield 4500. Any thoughts?

 

[MoonRise]

Sounds like the mix was too wet and/or he worked the mix when it was too 'wet' (when the 'bleed' water rises up to the surface) instead of waiting for the 'bleed' water to start to reabsorb back into the concrete.

(*another cause of dusting of concrete is a weakened surface layer from the use of 'direct vented' fuel-burning heater aka fumes go right into the area and do not go outside via an exhaust pipe of duct of chimney) which causes carbon dioxide to be produced from the fuel combustion and that carbon dioxide gets absorbed by the wet curing concrete and chemically destroys the top layer of the concrete. It's called "carbonation". It doesn't sound like that happened here to you though.)

Long story short, IMHO you are screwed and the top of the concrete is NoGood. At all.

Fix is usually to remove (pressure wash if you at 'lucky', and grind if you are not so lucky in how deep the soft dusty **** is) the top surface down until you actually get to 'good' concrete. And then, depending on just how far down you had to grind to actually get to 'good' concrete, you put some sort of top-off layer there. An epoxy type if you luck out and only had to just grind off a very thin layer of bad concrete, or a self-leveling concrete product if you had to grind off more.

Some concrete folks say to try a "densifier" type of product. I'm not so sure of that approach.

http://www.concrete.org.uk/fingertips-nuggets.asp?cmd=display&id=679

http://www.theconcreteproducer.com/how-to/concrete-production/preventing-dust-on-concrete_o

https://www.engineeringcivil.com/dusting-of-concrete-slab-surface.html

http://www.concreteconstruction.net/how-to/biting-the-dust_o

 

[Gerald O]

Sounds like the mix was excessively watered down, and a lot of the 'cream' floated to the top.

 

[Shea]

Yes, GhostShield 4500 or any other good densifier. It's an inexpensive option that will help. Remember that it takes about a week for a densifier to react before you judge how well it may or may not have worked. Just keep in mind that if the floor is real soft, a densifier will only do so much.

 

[LegacyIndustrial]

Stick a screwdriver into the slab and lean on it.
If it pulverizes the surface fairly easy then the remedy is a diamond grind with a proper sealer or floor coating system.

Densifier won't help unless the screwdriver test is negative for weakness.

good luck

 

[rtz]

Can rent a big floor grinder from HomeDepot. One of the floor vendors on this site has a good YouTube video with grinding tips and brush/pad selection.

 

[ConCretin]

Moonrise provided a good description of what your issue likely is. As has been mentioned, a densifier might help but usually the weak surface needs to be removed to stop the dusting. a few hours of grinding and polishing might not break the bank too badly.

Hack contractors add too much water to make their job easier. This leads to excessive bleed water and a weak surface. I hate to add insult to injury but he didn’t do you any favors with his unauthorized substitution of fiber for wire either. With excessive water comes additional shrinkage and shrinkage cracks. Fiber might limit the formation of cracks but won’t hold them together the way wire would.

If you haven’t paid the guy yet, don’t. Sorry you have to deal with this. Hopefully the floor can be made serviceable and will hold up.

 

[Jeeper89]

Unfortunately, I paid him in full the morning of the pour, everything looked and sounded good up until about 8pm I could tell things were going south. Even then he had confidence so I trusted that he knew more than I did. I will look into the grinder, but even a few hundred for the densifier would be hard to come up with at the moment. My kids both play hockey and my youngest broke his leg in practice on Jan 9th. He is out of the full leg cast and up and running around but the bills just keep coming in from that and next season deposits are due soon. Kids and family come way before my barn floor so it will have to wait. Thanks for the input. I am going to try to get the concrete guy to come out and see what he thinks. I doubt he will show up, but worth a shot I guess.

 

[MoonRise]

Try a pressure washer first before a grinder, if possible.

The weak surface layer of dusting concrete will usually come off with a pressure washer. Use a narrow fan tip, not a 0 deg 'needle' tip. And in this case, use the pressure washer to actually remove the top (weak) layer of concrete. As opposed to what you usually do with a pressure washer where you are trying to leave the concrete surface still intact and just remove the dirt and grime.

A 40x60 ft concrete slab will still take a while to try with the pressure washer, but it will still be waaaaay faster and easier and less expensive than using a diamond grinder.

As you use the pressure washer and actually remove the top layer of concrete from the slab, don't let the 'slurry' of concrete that you removed just sit there. You will have to actually use the pressure washer to not just remove the top layer of concrete but also to 'wash off' that concrete dust slurry off of the slab and not just let it sit somewhere on the slab.

 

[Jeeper89]

Try a pressure washer first before a grinder, if possible.

The weak surface layer of dusting concrete will usually come off with a pressure washer. Use a narrow fan tip, not a 0 deg 'needle' tip. And in this case, use the pressure washer to actually remove the top (weak) layer of concrete. As opposed to what you usually do with a pressure washer where you are trying to leave the concrete surface still intact and just remove the dirt and grime.

A 40x60 ft concrete slab will still take a while to try with the pressure washer, but it will still be waaaaay faster and easier and less expensive than using a diamond grinder.

As you use the pressure washer and actually remove the top layer of concrete from the slab, don't let the 'slurry' of concrete that you removed just sit there. You will have to actually use the pressure washer to not just remove the top layer of concrete but also to 'wash off' that concrete dust slurry off of the slab and not just let it sit somewhere on the slab.

I had thought about using a pressure washer, but then I am just left with a rough surface. If I seal it at that point I'm let with a rough surface for life. My goal in the beginning was a nice smooth hard surface that I could use a push broom to sweep of with ease. I would love one of these cool floors that looks like you could eat off it but I just don't have the cash flow to make that happen. What it looks like I am going to end up with is a 80 grit maybe worse that that rough floor that is a pain to sweep sawdust off. My broom finished approach on the attached garage has a nice overall look than my barn floor does. Sad but true.

 

[RPH]

Go for the grind. Look at polished concrete floors, smooth and beautiful floors, but expensive to have done. I was quoted $8.00 square foot. Too expensive for this kid. But in your situation I would look at renting the grinder and put the time in to get it right. Unless you feel feeding the legal system. Even then that’s a **** shoot. Good luck with whatever you choose. By the way I used Ghostshield 4500 and the 8505 products and have been very pleased with the performance. But my barn is a working shop just not an art gallery.

 

[Armorpoxy]

A couple of coats of a sealer like our Armorpoxy Acrylic sealer will work wonders to keep the dust down. Inexpensive and easy to apply and will make the floor a dream to sweep and keep clean.

 

[Jeeper89]

Well here I am a year and a half later and still fighting dusty floors. Every time I sweep the floor I get a little more gray powder. I did some work on my truck last week and I was covered head to toe in concrete dust. Even my wife (who was helping me replace my turbo) said "This floor *****!" I have given the concrete guy poor reviews every chance I get but it doesn't help my floor, just hope it saves some one else the trouble I have had.

 

[HotrodHR]

OK, so what did you do with the floor after all the advice? Pressure wash, grind, or nothing?

I think I would have tried the pressure wash first even if it resulted in a rough surface.

 

[Garage Flooring]

Yes, GhostShield 4500 or any other good densifier. It's an inexpensive option that will help. Remember that it takes about a week for a densifier to react before you judge how well it may or may not have worked. Just keep in mind that if the floor is real soft, a densifier will only do so much.

Stick a screwdriver into the slab and lean on it.
If it pulverizes the surface fairly easy then the remedy is a diamond grind with a proper sealer or floor coating system.

Densifier won't help unless the screwdriver test is negative for weakness.

good luck

Respectfully this is not a quick question on the forum and everything is fixed situation. A densifier and a sealer will help good concrete dust less but, as both of the folks above indicated they are not going to 'fix' bad concrete or a soft layer on top.

You may need to grind off a layer and go back with a good coating. Drop me an email with some more details and let's get a couple of different plants involved and find the best solution

 

[Jeeper89]

So far I have just been living with the crazy amount of dust and a floor that keeps getting worse. I just don't have the cash to do anything with it at the moment. So for now I am just glad that I have a hard surface that I can park things on and when I have to crawl around on. Someday I hope to grind it down and do something with it but that may be years down the road.

 

[MoonRise]

Pssst, all that concrete dust is NOT good for your health either.

Which is why OSHA has 'new' safety regs regarding grinding/drilling/whatever with concrete, because the dust IS dangerous to your health.

https://www.osha.gov/Publications/silicosis.html

https://www.lung.org/lung-health-an...silicosis/silicosis-symptoms-causes-risk.html

IMNSHO, at a -minimum- you MUST pressure wash that concrete floor to physically remove the weak concrete layer that is making the dust.

If the floor gets a rough surface from that, then deal with that stage as you can. Grinding or top-coating or whatever.

 

[ConCretin]

You raise a very interesting and potentially important point Moonrise - one I frankly hadn't considered. The new OSHA standards are directed at crystalline silica, which is present in the aggregates used in concrete. It causes a number of health problems including cancer when it becomes airborne

I honestly don't know how much this silica is released by dusting concrete. It isn't the same as sawing or grinding, which is what the OSHA regs address. I did a very quick internet search and didn't come up with much..

You could probably debate whether the exposure levels resulting from a dusting floor are a health hazard but it's safe to say a dusting floor might be more than just a housekeeping nuisance. To the OP, I think I'd get a sealer on that floor at a minimum....

 

[Jeeper89]

Hmm, it seems everywhere I turn something is going to kill me. I’m sure the chemicals in the sealers aren’t exactly safe either. I know that I should do something with the floor but it’s just not in the budget. Work has slowed to a crawl with no signs of improvement in the horizon. I’ve been actively looking for something else but since far no luck. Maybe I should apply to be on one of these home makeover shows. Lol

 

[LegacyIndustrial]

Hmm, it seems everywhere I turn something is going to kill me. I’m sure the chemicals in the sealers aren’t exactly safe either. I know that I should do something with the floor but it’s just not in the budget. Work has slowed to a crawl with no signs of improvement in the horizon. I’ve been actively looking for something else but since far no luck. Maybe I should apply to be on one of these home makeover shows. Lol

I talked with a Gent from Montana today. He told me there is a massive shortage of tradesmen in Montana. Pack a lunch and head North!!


Sent from my iPhone using Garage Journal

 

[ConCretin]

Hmm, it seems everywhere I turn something is going to kill me. I’m sure the chemicals in the sealers aren’t exactly safe either.

I tend to think many of the health scares we hear about are overblown but silicosis and related conditions caused by silica are something I take seriously. It would be easy enough to protect yourself from the hazards associated with a chemical sealer with a respirator during application as opposed to the constant exposure to cement dust while working in your garage.

With that said, I haven't found any source that says the dust produced by a soft layer of cement paste on a concrete slab contains crystalline silica. Apparently the cement itself contains what is called amorphous silica, which doesn't present the same risk. I doubt average activity on the slab would be enough to produce much crystalline silica from the fine aggregates in the paste. I'm obviously not an authority on the subject but thought I'd offer what I could.

 

[Jeeper89]

I talked with a Gent from Montana today. He told me there is a massive shortage of tradesmen in Montana. Pack a lunch and head North!!


Sent from my iPhone using Garage Journal

LOL it took me over a year to build my barn that still isn't "done" at 43 and considering that I have pushed a mouse around at work for 50 hours a week for the last 22 years I'm not sure I'm much of a tradesman anymore. I design plastic injection molds and die cast dies. It's what I wanted to do since I was in about 7th grade. I still enjoy it but there just isn't much work out there right now. I don't spend a lot of time in the barn these days although I did have a chance to delete and tune my Cummins truck. Then I had to pull the turbo to have it rebuilt, all part of the reason I just don't have the cash to do anything with the floor at the moment. I may buy or rent a pressure washer this summer and see what that does to the floor.