Reinforce concrete piers?

Neil_K

I need a nickels worth of free advice. I'm in the first stage of building a shed and have set 9 concrete posts, each using 12" form tubes. The shed will be 16' square. The ground is slightly sloped, so the first row of 3 will be 2" exposed, the second row about 6"exposed and the last row about 18" exposed. My problem - I bought "general use" concrete, not realizing "general use" was for setting fence posts.

I tooked about 40lbs of leftover concrete and poured it into a cut form. After it hardened (6 days), the S#$% just decintigrated when I hit it with a sledge hammer. Its like its too sandy or something.

My dilemna - tear them out (I really don't want to), or reinforce them by digging out around them down to the frost line (I originally went 24", the frostline is 18) and pouring concrete almost to ground level, then taking 4x8x16 cinderblocks and masonry cement and squaring the top, backfilling with concrete. Rebar if necessary.

Anyone care to advise? It would be greatly appreciated!

Thanks.

Neil

Unregistered

What did you wind up doing?

Hammertime

to be honest with you. If it were me I would dig out the footings and break them up. Start over from scratch while I was still able to. Just put the right footings back in. Better a pain in the arse and safe then easy and let it go and be sorry. If you're going to dig around them then might as well pull them up. Or I guess you could just dig new footings right next to the one's you already installed. Just put the right one's in right next to the other one's.

Teetorbilt

I'm with Hammer on this one. What you build ON is the most important part of the project. Do it right and you can build on it again and again.

Daniel O'Connor

If it were up to me, I would get slightly larger tube forms and plenty of rebar. What I am suggesting is set a rebar cage about a 1/2 inch larger than the orininal posts, then set larger tube forms around the existing post, (use Portland Cement) pour a wall around your posts and you should have as much reinforcment as you need.
If you don't understand what I am saying, please feel free to email me at caterpillartlb@Yahoo.com.

Neil_K

How ironic, a flurry of replies *after* changes were made. Thanks for the responses. Here's an update of what I found out/did:

First off, concrete doesn't reach 50% of strength until about 7 days. It takes almost a month for it to fully cure. I did go back to my rubble pile and it did not seem as weak as it was after a week.

I also wasn't concerned that concerned with the piers that only come out of the ground a couple inches, but I still reinforced them anyway. 20" square piers look a lot more sturdy than 12" round ones anyway, especially on a 16x16 building (I have 9 piers).

Quikrete makes a "Precision Grout" product that works under high stress and achieves up to 14,000psi. Since I couldn't get a larger form, I did what I said about digging out, filling with concrete and using concrete blocks around the piers from about 4" below grade to the top of the piers. The grout could be made to a flowable consistency and I poured it into the chambers. Oh, and I used plenty of rebar, too.

I know there's two different opinions posted above, but am confident with the results. My piers are now columns that look sturdier than what I've seen under some mobile homes (I hope they are). Besides, what do you do with a ton of used concrete?

Teetorbilt

Neil, sounds like good work. Did you know that concrete never quits curing? It just continually gets harder. I suspected that 6 days was not long enough to form an opinion. Congratulations, you are on your way!

Neil_K

Thanks Teetorbilt!

Hammertime

My bad! I thought you were having the same problem when I posted cause I posted about a month after you installed the footings. I was assuming it was still brittle enough not to want to work with.

Sorry about that.