Ready mix vs. mix your own

Whatever the shape of this pier, similar to the dimensions you gave, x the 20 piers you need, does seem to be a lot of material to mix by hand.

Being that each pier is under a cubic yard, yeah, you could do one at time, with a mixer you should be able to make enough to fill 1 form quickly enough. When mixing by hand, problem is, it may take too long to make enough material to pour at one time, I don't like cold joints(where previously poured material starts to set up and you are still pouring fresh material on top of that). Those piers are small enough to not worry about that I would think, say oppposed to doing a wall by hand. The other thing, is depending on which way you do it by hand, is the consistency of the mix, yes you can get all the seperate materials, portland cement, sand for fine aggregate, stone for coarse aggregate and follow a mix design, or you can buy from a reputable masonry supply house a good quality bagged gravel(concrete)mix deigned and tested for a certain strenght, ( don't add too much water, keep your water to cementitious material ratio the same) I'm not a big fan of what the big box retail stores carry, there are masonry suppliers who carry a better product in a bag. Not sure what compressive strength is required and if anyone needs to sign off on these piers prior to placing the mobile home, if so, best to make sure you achieve the strength needed, and as ridiculous as it sounds, you can take 4 test cylinders of one mix if you buy ready mix, to substantiate the strength when sent to a test lab for breaking. If you mix by hand you would need to make at least 1 test cylinder for every batch made, again..... this may not even be an issue for this application, but anytime it does have to be certified, tough to beat ready mix, if it fails, the supplier may be liable, not you, + all that wasted labor.

Not sure if these are to be excavated formed and poured or just trench poured (no forms), below grade, but I can tell you, if you want to get it done quickly, you should have enough to make an order without the short load charges. If the quantity is short, make a slab for a patio or think of something that you could make out of concrete, might help to avoid those extra short load costs, you already need the material anyway, and add 1/2 yard extra over, after a careful estimate of the actual material needed, won't be a short load order and you have a little extra, running short on a pour sucks to say it bluntly.

Rebar configurations for piers are usually vertical bars, wrapped with horizontal bars, kind of like a cage, but for these, a couple of vertical bars, maybe 2-4 of those per pier with horizontals tied to them, placed equi-distant apart, like a ladder, would be as far as I would go, and just vertical or horizontal alone in each one would suffice to make it simple, I doubt the loading on these will be anything to be concerned about, if it is just a mobile home, sounds more like ballast for wind loading, and the mobile home is being fastened to them for both a foundation and a tie-back, guessing on that.

If a truck has access, it would make ready mix an easy way to do this, yeah maybe it will cost you more, but if you were to mix all of that by hand, you would need a large capacity mixer, like what a commercial masonry contractor would use, and have the pre-mixed bagged concrete ( gravel mix) delivered on skids placed near the mixer, need a buggy to haul and pour into the forms or holes, use seperate materials like portland, sand stone etc. you will handle every bit of the material once with a shovel to mix it and again to place it. You may save some money on materials, but it will be labor intense to mix same.

If you are subject to any specifications or codes by a municipality, if you toss rocks, broken brick in there etc., the pier most likely would not be accepted if seen by an inspector, yes you can bury what you want in there and it would probably not be an issue for a mobile home pier, but each pier would be different, and if under a much more substantial load, would compress to failure at different strengths if tested to failure, yeah old timers did it in barn foundations and slabs, many are still around, each to their own on that, I don't like the practice for any foundation or pier to be honest, no consistency, and it could easily violate a mix design in my humble opinion.

I recently did 20 piers quite similar to the ones described here, I cannot imagine mixing the material by hand. I pre-casted them to set with a Cat 420 hoe, would have been nice to have them set to pour in place, but the location was not accessible anyway, and the material was free, they did an 90 yard pour for a high voltage powerline tower base, foreman gave me short notice about the material overage, well I put together those forms in a hurry, no way I was going to see a 3/4 to full truck load of 5000 PSI get sent back, the end product came out nice and they were easy to set later on.

Pooh Bear

You provide the water, they have a large mixer on a truck and mix the quantity needed on site.

As previously noted, there is little or no savings in mixing your own concrete vs having ready mix delivered---even if you don't put a dollar value on your time. What you gain by mixing it yourself is control of the situation. Just about every ready mix driver I've ever dealt with has been patient and helpful---I've even seen drivers help screed a slab when the situation was threatening to get out of hand---but they've got a truckload of concrete that you have to pay for whether it goes into your forms, onto the ground, or back to the yard to make barriers out of.

Even if your location is ideal for the truck to get to every hole in the ground without you having to scramble around with a wheelbarrow, you're not going to have any time to attend to any individual pier until they're all poured. While there probably isn't anything made of concrete that needs less attention than a big block in the ground, still it's nice to have a chance to tamp the mud a little as it goes in, adjust steel that gets knocked out of place, etc.

4.6 yards of concrete would be an enormous amount to mix in a day. It's 23 94# bags of cement, for one thing. A number of times I've had everything arranged as near to ideal as I could make it, worked myself to exhaustion, and never came near to mixing that much. That was alone, though. Two good workers can mix considerably more than twice as much as someone working alone.

One last thing to know: You can never have too many helpers involved in a concrete pour.

All the best, Stan

Stan