Synthetic Concrete Mix?

Erimess

I've got a front porch that has some little chunks coming off the corner, and also some cracks near that corner that look like someone's tried to fix them before. (I see a discolored line running across them.) I've had trouble finding contractors which is why it's now into December.

One problem is no one is "taking new customers" because they won't work when it starts getting cold, which is making me totally paranoid about doing anything right now, although I've got a guy who will brace up the roof for about $25-30 plus lumber.

So I've got this guy telling me he's got a synthetic concrete mix, and claims he can during it in this weather. We've got a few days running in the 50's, and the 5-day forecast doesn't appear to go below 30's. But it absolutely could get below freezing in December. Supposedly this synthetic stuff can handle temperature changes better.

Can someone confirm or deny this? And opinions on this "mix" of his? Thanks!

Canarywood1

There's no such thing as" synthetic concrete" that i'm aware of so you best steer clear of this guy,it's too cold to pour any concrete unless you can protect it from freezing,and that means heat,not acclerators that speed up the set because it will still freeze.

Erimess

Yeah, I just tried to google this and all I came up with was synthetic fibers that can be added to concrete mix. When I asked him if this was something added to normal concrete mix, he said it came pre-mixed. So it sounded like he knew what to do with it, but not necessarily what it consisted of.

Tscarborough

40 degrees and rising, no freeze within 24 hours is standard for concrete construction, no "synthetic concrete" required. What he probably has is a polymer-modified patching concrete which will work fine.

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Canarywood1

" no freeze within 24 hours is standard for concrete construction"

So your saying if the temps get below32 degrees beyond the 24 hours it wont freeze???

Polymer modified concrete is hydraulic cement with organic polymers added,that are dispersed when water is added,which means it will freeze if not protected.

Erimess

Not a big surprise that I'm seeing disagreement - certainly not unexpected. But given that I still haven't gotten a hold of the other contractors, and just the fact that disagreement exists, I think I'm going to just go with having someone brace up that corner for the winter and hold off til spring. Even if it worked, I'm not liking the big rush.

However, since this "synthetic" topic could come up again, anyone who still wants to toss in an opinion, feel welcome. I can always save this til spring.

Canarywood1

Probably the smartest decision you've made today.

MarkusAIC

There are some very good epoxy type concrete repair mixes available. Abo makes a few varieties for different uses. Search Abocrete, Abojet. There are a few others but I can't remember names for sure. I think Xypex is another one. To the best of my knowledge the better quality products are not sold at big box stores. I don't recall what the temperature rating is on these.
For any repair of this type or something where a contractor is going to use a 'specialty' type product you should always require the contract to state exactly what the product is. Manufacturer, model, etc. This allows you to research to product to make sure it is actually proper for your application. It can also keep the contractor honest.
Homeowner's should always demand that products are listed in the contract for any remodeling project. I've had to help resolve so many disputes over the years between homeowners and contractors that could have easily been avoided.

Tscarborough

Concrete (or mortar) that has set has no free water to crystallize (freeze) and thus damage the concrete (or mortar).

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Canarywood1

What a bunch of nonsense this is,i sure hope no one is taking ths guy seriously.

Here's an excerpt from a civil engineer on the subject.



As a civil engineer and a building inspector who's done nearly four thousand inspections, I've seen my share of examples of bad pours. What will happen if the frost gets to it is, your concrete will end up chipping away rather easily, and your porch will end up basically crumbling apart. Particularly along the outer surfaces. You'll most likely end up with a large rough chunk (what's left of the inner part that managed to cure and was relatively protected from the cold air).

Tscarborough

Yeah, well, just google "Cold weather concrete placement" and figure out for yourself if you want to risk it, but keep in mind polymer modified repair mortars set considerably faster than normal concrete.

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Canarywood1

"polymer modified repair mortars set considerably faster than normal concrete. "

It's high early cement with organic polymers,dispersed with water,and it WILL FREEZE after it sets,period.
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GBrackins

here is an article based upon the new ACI-306R-10 Guide to Cold Weather Concreting by the American Concrete Institute.

Hope this helps!

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Gary

"You get what you pay for, and sometimes free costs more!"

itsreallyconc

of course concrete freezes if the temperatures drop - even steel changes its properties due to temp,,, the main point has been made by tscar - once the conc takes its ' set ', freezing temps won't bother it,,, polymer modified concrete has been around for some time & no failures have been reported when used properly,,, we installed an epoxy floor coating yesterday on a garage floor - IF we had added aggregate it could be described as epoxy concrete yet no cementitious materials were part of the mix,,, we've done many jobs over the yrs using polymer-modified conc & no failures yet due to mtl's fault,,, if you can drive on it in 24hrs, i figger its good stuff 40* & rising - no freezing temps in 24hrs - we've paved many roads & they're still in use 30yrs later even if we had to use blankets a time or 2

tend to be sitting on tscar's side of the field on this topic ( as usual, he does know his stuff ! ) while the birds are on the other side

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if you hear it from a guy in the apron store, be VERY suspicious the mtl/method will work,,, when it time to build something together, they won't answer phones NOR help
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Erimess

Interesting replies. Good point to have the material in the contract.

Just as a note, there seems to be an assumption it's a "modified-polymer" when I don't even know that. Unless that's really the only thing it could conceivably be. The problem is that the guy I talked to couldn't/wouldn't tell me what the stuff was. And the more I think about it, the more I realize I didn't like a lot of things he said.

I had a different guy brace it up for winter, and that brace can then stay when the work is done.