Best way to source concrete for a long fence project

Question

I've done several small fence projects before, and hand-mixed concrete in a wheelbarrow for each post as I set them in place.

However, I'm now looking to build a wood guardrail around a parking lot at work, that requires 73 6"x6" posts. I'm going to need about 1.8 yards of concrete for the job. Hand-mixing is definitely out of the question, and it seems that delivered, premixed concrete is substantially less expensive than bags anyway.

I've never worked with a concrete truck before. I know that trucks supply premixed concrete for large areas like slab foundations, but is out out of the norm to have a truck come and fill each hole as we set each post? Of course, I'd have all the holes ready to go with posts in them and a level line set up, but this would still require the truck driving up to and stopping at 73 different spots within the parking lot, to deliver a small amount of concrete to each hole. A lot more time and effort than delivering an equal amount of concrete to a slab.

I've seen rentals of concrete mixing trailers, and of course, the rentable concrete mixers from the big box stores. It seems like there are several ways to skin this cat. What is generally most cost effective, efficient, or both? What would you do?

Answer 1

Delivery of ready-mix in a truck

This gets you a whole lot of mud fast. There are a couple of problems: First, the "short" (small) load fee may raise its cost by 50% compared to the per-yard price you were quoted. Second, they'll likely allow you something like 5-10 minutes per yard to unload the truck and may charge by the minute if you run over time. The unloading process may be sped up if you have several laborers running with wheelbarrows. Third, if the unloading is slow, not only might you pay an extra fee but you might also have the mud setting up in the truck (recall that concrete hardens through a chemical reaction, not through "drying"). This could be mitigated by requesting the mix have a retarder to extend its initial set time.

You-haul ready mix in a trailer

There may be a small-batch concrete provider in your market. They have little 1-2 yard mixer trailers; you bring a heavy-duty pickup truck and tow their trailer to your job site while it mixes. It's heavy; the empty trailer might weigh 3500 pounds and the concrete another 3700 pounds per yard. You could buy just one yard at a time (or even less) and make several trips to ensure that you have relatively fresh concrete throughout the job.

Portable mixer

Honestly.. this is the one I'd do. The main reason is that I frequently work alone or with one assistant, and this approach is the only one I consider practical for such a small "crew." Rent/borrow/buy a mixer large enough to do the concrete for 4-6 posts. (Could buy a used one and resell it when you're through.) Put a pile of sand and gravel on a flat bed trailer along with the mixer, bagged Portland cement, and a few buckets of water. Tow it around the parking lot as the job progresses. You can pipeline the job a bit by dumping the entire mixed batch out into a wheelbarrow or a few buckets -- then you can let the mixer run making a new batch while you're placing the concrete mixed in the prior batch. Size the batches so that the mixing time roughly equals your placing time and all of that is well below the initial setting time.

Answer 2

Two yards is a short load in my area, and you pay extra for a short load. On top of that, you don’t have much truck time. By the time you add truck time for 73 stops, you will find the cost is well beyond your expectations. I have a small hand mixer I use when I need a good mix in the hole. At the farm we dump the sakrete and water in the hole and call it good.

For a ready mix truck trailer delivery, you would have to have all the posts set and ready to pour. (You don’t want it to set up in the trailer as they are expensive.)

In my area, we have rental trailers you pull behind a truck for small jobs like this job at just under 2 yards for the mixer type that you probably need; with that many spots, a dump trailer could work, but it would probably start setting up in the trailer.

Answer 3

Buy a small electric cement mixer second-hand

The quality of mix is better than mixing by hand in a barrow, and of course is much faster. It'll also be useful for any other projects like paths, footings for walls, and so on. If you've got a large property, it's just generally worth having one.

You can buy new, and they're not too expensive. Cement mixers are tough though, so buying second-hand on eBay is totally fine and will save you a little money. So long as it starts, runs, and the drum isn't full of dried cement as a sign of past misuse (or covered in dents from a previous misuser chiseling out cement), you're good to go.

Sure, you can hire one instead. But if you buy one off eBay, use it and then put it back on eBay, you'll get basically what you paid for it. So hiring one is a waste of money.

Answer 4

Concrete aggregate ( sand and gravel at correct ratio ) minus cement.

I get a dump truck load of that and then buy bags of portland cement. The ratio for mixing is 1 part cement, 5 parts navy jack. So one bag of cement will make 6 bags of concrete. Rent a 2 bag mixer and then barrow it to each hole.

Answer 5

In the UK we get "Postmix or Postcrete" and it comes in a bag.

Dig hole to correct depth and width relevant to post size. Fill hole approximately a third of depth with water and place post in hole. Pour in postmix evenly around the post until no standing water is visible. Position and level post as required. ... Do not mix postmix with water by hand or machine.