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RE: Grout in lieu of conc.[Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: <seaint(--nospam--at)seaint.org>
- Subject: RE: Grout in lieu of conc.
- From: "Joseph R. Grill" <vveng(--nospam--at)cableone.net>
- Date: Mon, 18 Oct 2010 08:35:40 -0700
Thanks to all that have responded to my question. Harold, ASR checks is a very good comment, that had slipped my mind and will certainly be brought forward in discussions. This project is not a large structural project, but a “water feature” bridge at a residence. Yes, “grout” was an incorrect term, I used it because that is what the contractor used. All the cautions that have been brought forward are very pertinent. However, I haven’t found anything in my reading or within any comments that strength is an issue and I am certain that will be one of the questions to me. The concrete will not be directly exposed to the elements and since it will be located in a back yard in AZ will not be subjected to any de-icers. I guess the bottom line is I hesitate to say a “crushed” gravel aggregate cannot be used since it doesn’t appear strength is an issue. I can take precautions and add additional reinforcing to help with the cracking.
Joseph R. Grill, PE
Verde Valley Engineering, PLLC
It's not really "grout" unless you're using it for masonry, in which case it would need a slump of about 9 inches or more. But what you describe is pretty lousy concrete.
Shrinkage will be a big issue, and is really unavoidable because of the extra water needed to coat the increased surface area of smaller aggregate (much larger surface area for same mass of pea-gravel vs. 3/4" or 1-inch rock). Pea-gravel mixes are usually about 55% sand, 45% gravel. Best mixes that can be 'tail-gated' or pumped with boom-pumps are 65% rock and 35% sand.
I really dislike pea-gravel concrete that I've seen; furthermore I question the economics of using a pump. While placing concrete for one phase of my own recently-completed basement project, I hired a "rock-pump" that could hande 1-inch aggregate. It took 3 or 4 guys to haul the pump hose around, the line clogged once or twice because the overkill engineer (moi) wouldn't add water to the mix, and the pump guy dumped a big pile of waste concrete next to my driveway. For the next phase *I* was the "pump." I wheel-barrowed about 6 CY of concrete into place (spent about $30 extra on 'stand-by' time for the concrete truck, but saved $200 on the cost of a pump--not to mention the 3 guys to drag the pump hose around). Most recently I was one of 3 guys who carried concrete in 5-gallon buckets to dump into the top of the last section of wall forms.
Unless you have to work off of a scaffold, I'd bet that moving mud by wheel-barrow is as fast as, and cheaper than, a pump--and you get much better concrete. But what do I know, I'm only a structural engineer and builder....
From: "Joseph R. Grill" <vveng(--nospam--at)cableone.net>
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