Why is bagged Quick Set concrete "not for structural use"? 3

[Tomfh]

Bagged quick set concrete always says "not for structural use". What is "structural use" in this context of bagged concrete? and why do they warn not to use it? Is it because of the way it tends to be used, e.g. with limited control of water content? Is it because of the speed of set, which make it difficult to place and consolidate prior to it going off? Or it there something about it that really is no good for structural use?

 

[rb1957]

if it breaks then it was a structural application (and concrete liability is protected).

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[WARose]

I'm almost positive I've seen info on Quikrete (to bring up another brand) bags that say it conforms to [this and that] ASTM numbers. Don't recall any label saying something like in the OP. (But you never know. Like the others have said: QC isn't good with that stuff.)

 

[JStephen]

What is "structural"? In past research, a structure is "that which is built" and therefore includes buildings, bridges, rocking chairs, cars, rockets, boilers, engines, transformers, printers, wristwatches, etc.

 

[Tomfh]

How does the cost of this compare to a structural mix?

Slightly more than the regular version:

There's no significant difference in quality, if indeed any difference. I have used both types extensively and they are both perfectly good concrete. The only difference I've noticed is that the quick-set simply goes off a LOT faster. I suspect this has to be the primary reason for the warning, as opposed to some fundamental deficiency with the product itself.

Also like you said marketing plays a role. Quickset for "non structural" things like fences, posts. Regular blue bag for more general purpose, and then their "high strength" grey bag version for "structural" applications.

 

[Tomfh]

Great if you just want to have a bit of concrete to put a post in the ground or make a small footing for a shed or something similar,

This is what got me wondering about the "not for structural use" warning. I've heard builders and landscapers say you can't use quickset concrete for a shed or deck footing. By their logic sheds, decks and their footings are "structures", and quickset is for "non structural use only".

 

[WARose]

Even though it may not be official.....that stuff does last pretty good. In the thread below are some pics of some things I built when I was a teenager (about 30 years ago). The first one is a dam made of rocks and concrete. (You can see the small pond behind it.) The dimensions on it are about 30'x5'x4'. Basically me and my brother built it by putting a pipe down, covering it with rocks, then covering the rocks with the kind of sacked concrete we are talking about here.

The second one is a shallow crossing (over a creek) I built (by myself) for a 4-wheeler trail. The dimensions on it are about 40'x4'x2.5'. The worst part was getting that RC pipe down there. (You can see the water flowing from it in the pic.) I tried dragging it at first but was scared it was going to roll over me on the downhill parts. (Finished getting it there with a Bobcat.) Covered it with rock.....then covered the rock with that sacked concrete.

https://www.eng-tips.com/viewthread.cfm?qid=435705

 

[dhengr]

Tomfh:
My thoughts on the matter... As long as the product is not produced by some local, fly-by-night, outfit, I would expect pretty good product QC from bag to bag, and product to product. They have a reputation to protect, they aren’t shoveling the various ingredients into the bags with different sized, broken shovels. They are batching it from known raw materials, dry mixing it, and properly dispensing/bagging it. And, I’ll bet they have batch mixed ingredient testing and wet-mixed strength testing too, for consistency and their own protection. The “not for structural use” verbiage is mostly legal beagle stuff to cover their butt. However, the product sets so quickly that there is not enough time for placing, consolidating, and serious finishing for real structural applications. But, most end users won’t know that until it is too late. Their biggest concern is dumb end users who mix their concrete in buckets, wheelbarrows, and kids pools, with canoe paddles, shovels or garden rakes, and measure water by the bucket full. That’s where most of the inconsistency happens.