So you don't wear a dustmask eh?

[augerpro]

It's often mentioned on here how nasty MDF dust is yet many of us don't wear dust-masks and I see pics with people covered in dust. Since I work at an oil refinery I've never had a problem wearing a mask or ear plugs or anything. It's just natural for me to throw on PPE (personal protective equipment) before starting work. Here is a good example of why you should too:



I was sawing MDF outside a couple weeks ago and the dust dropped on the snow below. That's what happens after a couple weeks of MDF dust and moisture. Now just think of what happens in your wet lungs after a day here and a day there of breathing this stuff.

[Gir]

Is that mold growing on top or is it actually eating away at the concrete?

[augerpro]

It ate the concrete. Quickly. At first I was kinda pi$$ed because I just built this house a year ago. But it IS a driveway, and these things happen, so oh well.

[cjd]

:E

Not much else to say.

I'm very very glad I stick with birch ply. Very glad.

C

[kgveteran]

I'm glad I use a cabinet maker

[ThomasW]

MDF dust isn't 'caustic', after all it's simply sawdust and pressure setting resin glue. Were it caustic, geezers like Chasw98 and myself would have died from exposure decades ago...

For multiple years in winter I've had piles of it in snow at the sides of the driveway, and there's never been anything that looks like that.

That picture looks identical to salt damage, or more likely since this is new concrete, it was improperly cured or it was a 'bad' mix. Expect more of the same as time goes on regardless of whether there's MDF on it or not.

[augerpro]

Not salt Thomas. That's exactly the spot the dust was. In fact I avoided walking on it for weeks so I didn't track it into the house. At the top of the picture is a darker area where I couldn't sweep up the debris cleanly. When I looked closer it's still got dust stuck to it. So I need to get out there and hose it down my driveway before it eats away some more. I don't think panels would cause this. The surface area is very small with a panel, so exposure is less. It's the fine dust that has very high surface area and thus contact with the concrete. I agree teh MDF isn't caustic, but there is definately some chemical that when mixed with moisture and concrete does this.

[Amphiprion]

I've had wet MDF dust on my driveway long enough for it to get very moldy, and it never did anything like that.

[augerpro]

Hmmm. Maybe it is salt. Although why it would do that in the only area that had MDF dust is peculiar. The rest of the driveway is fine. Perhaps someone would like to experiment with THEIR driveway :B

[ThomasW]

I'm pretty sure but it's either salt, improperly cured concrete job, or bad batch.

There's a house a couple blocks away that was facelifted including new driveway. After the first winter it had a couple patches that looked exactly like that. Now the entire drive is trashed and no one there does any woodworking.

At your place I suppose it's possible that the MDF held moisture in the concrete that froze, then expanded knocking off the 'creme' layer.

But.......

I'm always leaving piles of MDF dust sitting on the snow at the sides of the driveway. I've done that for the 20yrs I've lived in this house, and I have nothing that looks like that........

[augerpro]

I think you may be right about the dust holding moisture at the surface Thomas. The debris was kind of like chips. In fact you can see some big ones in the pic. The darker area at the top which still has dust is moist. The area that sweeped up easy is dry. Strange.

[augerpro]

So I guess the message here is don't let wet MDF dust, um, freeze to you lungs. Your lungs may chip, or something...

[ThomasW]

I think you may be right about the dust holding moisture at the surface Thomas. The debris was kind of like chips.

Chips, yep, and that's why I'd bet if you post that pic on a home improvement forum you'll be told either salt, improperly cured, or bad batch.

The MDF may have accelerated the process, but it's not the cause.

[Dennis H]

If that's a new driveway (first winter) complain to whoever made it and don't mention the MDF to them, it's not a factor. You got a bad finish -- maybe it was setting up too fast on a hot day and they sprayed too much water on the surface while they were trowelling it down, leaving the surface coat weak and subject to freeze-thaw damage. The surface got diluted and then dried out to a chalky surface instead of doing a proper chemical-reaction cure. Or maybe they poured in cold weather and the surface froze, leaving a weak surface. Like Thomas said, the rest of the driveway will end up the same way over time. The MDF dust just helped it go bad in that spot first but it's not the cause.

[oxcartdriver]

too much water on the surface while they were trowelling it down, leaving the surface coat weak and subject to freeze-thaw damage.

My driveway did the same thing in spots where it was to wet at the surface. To wet, more solids fall out of the mix, weak surface, freeze-thaw cracks it up.

[Paul H]

If that's a new driveway (first winter) complain to whoever made it and don't mention the MDF to them, it's not a factor. You got a bad finish -- maybe it was setting up too fast on a hot day and they sprayed too much water on the surface while they were trowelling it down, leaving the surface coat weak and subject to freeze-thaw damage. The surface got diluted and then dried out to a chalky surface instead of doing a proper chemical-reaction cure. Or maybe they poured in cold weather and the surface froze, leaving a weak surface. Like Thomas said, the rest of the driveway will end up the same way over time. The MDF dust just helped it go bad in that spot first but it's not the cause.

Those are possibilities, but it's more likely a fundamental problem with the choice of concrete mix. Concrete that's intended to be exposed to frost, especially horizontal surfaces, should have 'air entrainment' in the mix.

Air entrainment is a chemical additive which forces microscopic bubbles of air to stay in the concrete during set-up, and thereafter, providing expansion room within the concrete material for it to expand and contract during freeze-thaw cycles without cracking. If the concrete doesn't have air entrainment it will tend to spall off from the surface, like in those photos.

Use of air entrainment is standard practice in cold climes for exposed concrete. An easy way for a laymen to get a good mix for a driveway or garage slab is to ask the concrete supplier for the sidewalk mix used by the City you live in - it will be a mix that's been properly specified, reviewed and tested.


Not to take anything away from the initial purpose of this thread - wearing a mask while cutting mdf is excellent advice.

[Andy_G]

If you have chips, then what you have is called "spalling". What has happened is a differential freezing of water in the surface of the concrete, probably held there by the MDF.
As the water alternatively freezes and thaws it cracks the suface off the concrete.

[crackyflipside]

Ok, I guess I can actually give some (semi)professional advice on this very subject! (I'm going for my BA in Construction Management and just passed construction materials last semester with an A )

MDF, by it's material composition, is just wood fibers and synthetic resin binders to hold it together. Now if for some very strange reason the MDF was treated for decay/insect resistance it would also have CCA (Chromated Copper Arsenate) which is being slowly phased out by Alkaline Copper Quat (ACQ) and Copper Boron Azole (CBA). But those preservatives would be really strange to find in an MDF board because MDF is used almost exclusively for indoor furniture and moldings which will never really see any outdoor conditions.

Concrete is your culprit here. Concrete is pourous so water will find its way in. When water freezes, it expands, and it expands much faster than concrete does. Frost will crack concrete. When pouring concrete in an environment where the water will be freezing and thawing, one must put the right admixture into the concrete before it's poured. An air-entraining admixture is used so as the concrete is curing, small microscopic air bubbles will form inside and will provide adequate empty space inside the cured concrete so water can expand and contract without putting pressures on the concrete.




edit: Damn, it looks like Paul beat me to the punch!

[kingpin]

So does this mean I can still eat mdf dust. :
I have plenty more helpings coming. Center and rear speakers, and a subwoofer. :T

Mike

[Andy_G]

Eating of mdf probably isn't a major problem. The glues aren't particularly toxic, a little bit, but only in largish quantities. And the saw dust, well there is enough in sausages anyway, its the fats that give you the flavour..

Its getting it into your lungs that is bad !!

[jimluu]

I thought that the biggest worry about MDF is formaldehyde in the glue, which in large quantities is a carcinogen. MDF dust is so fine though that it can get into the lungs. I'm not sure how the lung process it, but I'm almost certain that it can't metabolize it. Most likely, a form of mild inflammation will occur at the level of the lung lining, which with repeated exposure will lead to stiff lungs. Coal miners' lungs. You probably won't find out until later years.

[jonathanb3478]

I believe another primary worry with MDF is the very small particle sizes. The really small ones can penetrate cell walls and build up, since there is no method in the cell for removing such small contaminants. This causes health issues in the affected tissues, IIRC.

And I do mean very small. By and large, dust collection solutions are just a pump for particles that are this small, not any kind of filter. I work outside and point my "dust pump" out into the depths of the backyard for this very reason.

[chasw98]

MDF dust isn't 'caustic', after all it's simply sawdust and pressure setting resin glue. Were it caustic, geezers like Chasw98 and myself would have died from exposure decades ago...

Well, h*ll, if all I have to worry about is MDF dust, I will live to be a hundred! Remember us 'geezers' come from the day when eating the paint on the windowsill of your house tasted good! Before they took the lead out, not to mention our early education, asbestos and all. And then as we grew up, there wasn't a chemical we wouldn't injest in the name of fun! So, a little dust here and there is just good for my immune system.

Fellow geezer, Chuck

[PMazz]

You had window sills? When I was a kid....

Pete

[Rolex]

Air entrainment in the concrete will help, but it's no guarantee that it will keep things from spalling. Freeze thaw is brutal and will destroy any concrete over time. It's not the salt, or the mdf, it's the freeze/thaw cycle.

Concrete gets much harder over time. I'm not talking 28 day break tests or 56 day break tests, I'm talking years. It's much more unlikely you will see freeze/thaw issues with a driveway that's been down for 20 years, if you haven't seen it already.

[chasw98]

You had window sills? When I was a kid....

Pete

Pete:
Are you an older geezer? Not many left around.

[ThomasW]

Pete:
Are you an older geezer? Not many left around.

Pete's no spring chicken, but he's got a few years before he's a card-carrying geezer..

[chasw98]

Pete's no spring chicken, but he's got a few years before he's a card-carrying geezer..

Well, I turned 55 today. Does that make me card carrying or wannabe?

[ThomasW]

Well, I turned 55 today. Does that make me card carrying or wannabe?

Well it's official, Chuck is a cardcarrying geezer..... :E

Happy Birthday.... :T :B

[---k---]

If anyone would like to see my certificate for being a member on ACI Committee 364 and 546 (Rehabilitation of Structures and Repair of Concrete), I can probably did them out of a box somewhere.

Anyway, several people are correct and several are very close. This is very common. It is usually a combination of lots of things. Primarily, it looks like the concrete was over finished and not likely air entrainanted. The combination of these caused it to be very susceptible to freeze-thaw deterioration. A $1000 petrographic examination would tell you for sure. The MDF was in no way a factor.

If I were you, I would look to see if your 1-year warranty is still effective and ask for the drive way to be replaced. The problem you see is only going to get worse. If you do not have a warranty, I advise that you live with the current damage and put down a 100% Silane sealer to stave off additional deterioration. Silane is a water-repelling clear sealer, that will need to be reapplied every 5 years or so. Brand name that I typically specify is Hydrzo by BASF, but there are dozens of them on the market.

Shallow concrete repair products to cover up the problem are typically not effective in the long term. I would be leary of any of these type of repairs.

[Andy_G]

The MDF was in no way a factor.

Except perhaps that it held moisture on the surface of the cement.

Spalling will generally not happen unless the water source is pretty regular/ constant. Generally, moisture must be retained on the surface for the freeze/thaw effects to happen, which is why it is more prevalent near the sea, and why concrete designs have to take this into account.

I might add that concrete design also has to take into account the salty air when near the sea, as well as moisture problems. A combination of both can lead to much more significant problems if the reo should get salt and moisture into it.

And you all thought concrete was just concrete ;-))

[EdL]

Now we are on the right track! Since the fissures created in the weak concrete through repetitive freeze-thaw cycles began...we have small-scale pot holes...the sort you hate to drive through...
If you can't get your contractor to replace your driveway (which he should...), when the concrete dries out, SEAL IT. Many "name brand" products are available. None are a better value than boiled linseed oil. Cut it with mineral spirits so it flows better...consider a pump sprayer for application. Repeat as needed...certainly again next fall before the cycle repeats itself.

And you thought this thread was about mdf?

[augerpro]

I'm just outside of the one year warranty but I'm going to call the builder anyway and see what they have to say. I'm kinda bummed now, thinking the whole driveway might eventually be like that. I'll have to look into that sealer just in case. Thanks everyone for the advice so far ;x(

[Dennis H]

I'm just outside of the one year warranty

That implies your slab was poured in the winter or the late fall when the temps can get below freezing at night. Good practice would have them laying insulated blankets (like 2" thick) over the new slab for several days to keep it from freezing up at night until it's properly cured. If they didn't do that and the surface froze, that could explain your problem.

[Andy_G]

That implies your slab was poured in the winter or the late fall when the temps can get below freezing at night. Good practice would have them laying insulated blankets (like 2" thick) over the new slab for several days to keep it from freezing up at night until it's properly cured. If they didn't do that and the surface froze, that could explain your problem.

Yep, small cracks already in and under the surface, then mdf held the moisture in through the recent cold weather, causing the spalling that we now see.

Makes sense.

Certainly if it was properly laid in the first, of the right grade concrete, laying and curing procedures etc, then this damage should not have happened.

[digital desire]

When I brought home my new wmtm center channel, my Wife immediately commented that the (raw) MDF smelled like dirty feet. I never noticed before, it kind sorta does!

[EdL]

sleuthing

I love concrete. It has put a lot of food on my table. I've seen both extremes of the spectrum. You shouldn't see this happen to your driveway.

er...forensics? It is unlikely for residential work that there would be test reports for samples collected from your concrete. Ask for them anyway.

If they did it that way last year chances are they are doing it the same this year. You could visit a driveway under construction and see for yourself.
The builder is at the top of the chain of responsibility, then the guy who placed it, then the concrete supplier.
The builder may have self-performed...done it with their own crews. They may have sub-contracted the work to another contractor. Your builder doesn't want a bad rap in today's declining market. Be prepared to squeak LOUDLY if an amiable approach doesn't get results. I would tell my builder that his warranty of one year includes all 4 seasons. That what you are witnessing could only become evident under the climate conditions normal for your area....and it takes this long for such a situation to become evident. Bear in mind the spalling appears to be moisture related (freeze-thaw) and not salt. If he tells you now that concrete needs to be sealed he should have told you then...or done it himself. (do a google on "concrete curing")

The supplier of the concrete doesn't want a bad rap for faulty materials. This is not to suggest the concrete was bad upon delivery. The addition of too much water to concrete (to ease the placement of it at the site) will wreck an otherwise suitable material. In that case, the supplier would be doing what the buyer (the guy placing the stuff) directed him to do. Also, as noted above, too much water could have been added to the surface of the concrete during the "finishing " phase (to make it "easier"). These are 2 ways to cause what you are experiencing. One of them affects all the concrete. The other is at the surface.
If you wish, invite the concrete supplier's sales rep or QC guy to see what is going on. Bear in mind he won't want to alienate one of his customers. He will defend his product.
It is not an enviable task you have before you. You do deserve what you paid for.

[Lurkalot]

MDF and respiratory protection

The issue with MDF is that cutting it creates particles that are of a "respirable" size (they readily pass through the defenses of your upper respiratory tract). I cut a lot of MDF, and use a half-mask cartridge respirator (properly fit-tested), fitted with HEPA cartridges. You need at least an N100 The typical white paper disposable respirator you can buy (N95 rating) is NOT effective at capturing the smallest particles (respirable dust is typically considered to be particles of 5 microns or smaller in diameter (depending on whom you believe:>).

Your health is easily worth $40.00, so buy a cartridge style respirator with HEPA cartridges (N100), get fit-tested for it at the time of purchase and the really enjoy the after work beer you deserve for cutting all that MDF :>)


Work Safely,
Lurkalot

[Andy_G]

I have to comment..

"Lurkalot" .. what sort of name is that..

"Sir Lurkalot" .... please... you could even build a round table then. !!

and beer is used washing the mdf down, you don't deserve a beer if you wear a mask !!!

[Rolex]

Okay, the concrete supplier will not care in the least about your driveway. He doesn't have to stand by his product. He will blame it on conditions, or improper placement. I highly doubt this is a mix issue, as it was probably a standard mix that was sent out. The supplier will have records of what they claim the mix to be. Talk with the builder, but my guess is he is going to tell you you are out of warranty. For what it's worth, one year does constitute four full seasons.

Because it happened to this small portion of your driveway DOES NOT mean the whole driveway will look like that. It could, but very unlikely. I will say though that the spalling that has already happened will get worse as the years go on.