Foundation Pictures

[CKillgore]

Okay. I guess the only hesitation with the vibrator is I know it is gonna be a good bit more expensive than putting in the superplasticizer. The only place that rents stuff in town overcharges for everything.

 

I'll think about it though. It may be the best solution.

 

Thanks guys.

[njanvilman]

Remember, you only pay once to rent the tool, but you have to live with your foundation a long time.  I always try to do it the best way the first time.  With concrete you do not get a second chance.

[Dave51B]

Ok.....just thinkin' out loud....Got an air chisel ? Maybe vibrate that cage a bit ......Hmmm, air chisel.....hot iron... I wonder.....naaa ,no way.....  Dave 

[patrick]

I've done foundations with plasticizer and without. It doesn't seem to make that much difference for a hammer foundation. 

[DSW]

Ckillgore, sorry I was out of town when you 1st asked this question. A few random thoughts on the subject before I sack out.

 

We used to vibrate steps using a cheap 1/4 sheet palm sander on the forms. I know chimney liners use then to consolidate the grout the use when they reline a chimney.  An air chisel on the bar would work to a certain degree. I've seen guys run the vibratory plate compactor up against wall forms to help vibrate the crete when the vibrator broke in the middle of a pour. In one case they ran the plate right down the top of the length of the wall forms. The "old school" way to consolidate concrete is to "rod" it. You simply take a long piece of rebar and pump it up and down in the crete in the areas you want to work and the juking motion helps consolidate the crete. In a deep footing you'll have to rod in layers. Sort of like churning butter.

 

One option with Super P is to pour your sidewalk 1st, then pour your footing after you wet up the concrete. That what we used to do when we had to pour steps or areas with heavy slope and didn't want the concrete to have too much slump and have it run on you. It's not hard to figure volume if you are careful. 80 sf of side walk 4" deep is 1 yard. Typically if you use 2x4's for forms and rake 3/4 clean stone to the bottom of the 2x's, when you hit the stone with a plate compactor, the depth usually comes out to 4" maybe slightly less. If you don't compact the stone ( which gives you a nice flat surface that's easier to measure for crete) then assume your depth is 1/4" to 1/2" deeper than the tape shows. Lay a 2x4 across the forms like you plan to screed and measure depth. If you aren't familiar doing this sort of work, measure every 2' or length and keep tract of your depths. If all are within 1/4", use the deeper measurement to run your numbers. If depth varies greatly, either add more stone to get an closer average, or work depths in sections, 15'x3' wide 4" deep, 15' x 3' 5" deep etc and total all the volumes up. On a curved walkway, we used to take a 300 ' fiberglass tape and run the length down the middle. That gives you an accurate average.

 

 

So you figure you need 2 yards for your walk way ( 160 sf 4" deep)  then you need 6 yards for your footing...  POur out your 2 yards to do the walkway, then wet it up with the super P and pour out the rest. Order 8 1/2 yards minimum to be safe. 1/2 yard goes away fast and is a lot cheaper than running out and having to have them send out a cleanup of 1/2 yard to finish the job. When I worked crete we could work it to an extra 1/2 yard per 10 yards. When one of the other guys did the math, we'd order 1 yard extra minimum. The question was how accurate I was vs them in getting the depth right and working curved areas in square footage.

 

If you pour the walk with super P in it ( assuming it's not like soup) say at a 5 slump that is workable, but too wet for a heavy slope, pour it out and leave it a hair high and don't screed or work it right away. Super P kicks out after roughly  30 minutes and it will go from wet back to whatever it was sent out at in minutes. If it came out really tight, say a 2 slump, you may have a lot of work to do if it's a big area. If it's not really big, say less than 100 ft by yourself, you can go back and finish it quickly before it's too hard to work well. Having an extra wheel barrow or two of "scrap" concrete or a pile on the ground you can dig out of to fill low areas can help. When done, let the concrete set until you can't stick a shovel in it and you can break up the lump easily with a pick or sledge to make it easier to dispose of in bit size chunks. As long as you break it up within an hour or two, usually you don't have to exert yourself.

 

 

Keep in mind a good driver is your friend. A good driver should be able to get you the slump you want when he adds water or Super P on site. Front loaders often have slump meters that can help a driver tell how wet a mix is. Old timers or guys with plenty of experience can do almost the same thing simply by sound. If you know how dry the mix is to start with ( we'd always pour some out in the chute to see it in person before adding anything if it was critical) the driver should be able to change the mix to what you want, say from a 3 slump to a 6 slump. It's not always perfect, but it's easier to add water than take it out, so go slow in stages if need be.

 

 

Given a choice, screed uphill. If screeding a cross slope, angle the 2x so the leading edge is down hill, and keep taking a mag and pushing the extra crete up the hill in front of the screed. If you have a low spot, take a mag or two full and fill the holes vs rescreeding. If anything when it's too wet, leave the crete high, then come back and re screed after it sets up more.

 

 

I'll assume since you are asking about Super P, that you are planning to order a truck vs mixing it yourself. If mixing yourself, that's a whole different ball game we can discuss separately. If I was having crete sent out with no Super P to be added, I'd probably have it sent out at between a 4 and 5 slump. That's wet enough to screed without too much trouble over a narrow area like a 3 or 4' sidewalk by yourself, but wet enough to pour between bar reasonably well. From the plant they usually add water reducers to wet up a mix rather than water. This leaves you with the compressive strength you want, at the slump you request.  If need be you could wet it up to say a 5-6 slump with a few gallons of water without seriously compromising your strength assuming you are starting out with a 300-3500 mix to begin with. Note higher PSI cretes like 4000 or 5000 mix have more cement and tend to set faster than cheaper mixes like 2500 or 3000 mix. That's some times important to know when working with something like Super P. You may find when the crete snaps back after the Super P kicks out that it may be a lot harder than you expect it to be.  4 or 5 slump wetted up to say a 7 or 8 can suddenly unexpectedly start acting like you have a 2 slump to deal with. This makes it good for footings, but not always good for finishing slabs or walks. Up side of high strength crete is a bit of water doesn't hurt it as much as your water to cement ratio is still high.

 

 

One other thing to think about. Harbor freight sells a cheap vibrator for about $100 and you can reduce that with one of the easily available coupons. My rental place rents a vibrator for  about $50 for 4 hours and $70 a day to give you a reference to gauge your place against. Their vibrator is a bit short ( tie it to a rope and lower it down in the hole possibly with it locked on) but it might do the job for you. I wouldn't recommend it for lots of work, but for one job you might be able to get away with no problems. Then toss it on CL for 1/2 or 1/3 what you paid and come out cheaper in the long run.

 

Feel free to PM me if you have questions. I'll be happy to try and answer any I can.

[CKillgore]

DSW,

 

That is a wealth of information! I really appreciate the time you took to type that out. That clears up a lot of stuff for me. 

 

Thankyou very much!

Cody