I've a hole with a metal post in it, around 30 inches deep, i'm hanging a 12 foot field gate on it. I like the idea of putting a bucket or 2 of water in the hole and dumping a couple of bags of Postcrete in it vs making a mix of concrete.
What do others think? I've read that it's not quite as strong as concrete.
TIA.
I have used it but for fence posts not gate posts, it works ok for that application. I doubt it needs to be that strong - just heavy and able to take a high compressive load.
It's not as strong as regular concrete and it takes longer to harden - I'd not expect it to work well with a large gate unless you used an oversized post to spread the load. My experience is that you usually need more bags than you bought (but maybe I'm just bad at digging neat holes).
I found with 24" holes and 4" square posts, it was a tad under two bags. For a large gatepost, you probably ought to allow for four.
My holes looked like:
I thought postcrete had accelerators in it to ensure it hardened quickly, and the post didn't have to be supported vertically for any length of time before the concrete set.
Quite. It sets incredibly quickly.
Tim
My technique for *agricultural* gateposts is to backfill the hole with smallish rubble (broken bricks, concrete etc.) and then pour in a runny cement sand slurry.
I've never hung a 12ft gate from a metal post, but it strikes me that the soil might make a difference. The post fixing that works in heavy clay might fail in light sandy soil.
I hung a 7ft gate off a wooden post simply inserted in a very deep and close hole and packed hard with clay. its still fine. The secret is the depth below ground, not the postcrete. Years ago we had a washing line pole in the parents house. It slowly pulled out of te ground taking all the concrete it was in, with it.
Last storm a poorly fixed 8' concrete fence post blew down. Poorly fixed as at the time we had a shed in the way and the neighbours side was close to their concrete path and the fencing guys couldn't get proper access. Anyway, I dug out a square hole suitable for the job and thought I'd use Postcrete. Bought 2 bags but realised it would be very short so, having half a dumpy of chippings-to-dust left over and some sand I mixed the post-crete powder up just like concrete though I can't remember exact ratio but I'm fairly sure it was 5:1:1 (chippings, sand, postcrete) using the PC just like regular cement powder. Bit of an experiment but I thought it's no different to packing the hole with lumps of hardcore only better and looking at the Postcrete powder it appeared to have a high percentage of cement to sand ratio.
Needless to say, it still set hard in 5 to 10 minutes, I did pre-mix the water with the powder before chucking it in the hole.
We've since had a far bigger storm than the one that took out the post and it's still super solid.
So don't be afraid to bulk out postcrete hith ballast, it absolutely works just fine (blue circle stuff does at least)
Railway sleepers are good:-)
The other agricultural technique is a strainer wire to a second, smaller post in the fence line. Usually a doubled length at 45deg. of barbed wire tightened by rotating an inserted bar.
The initial set is rapid but I recall it remained soft and powdery several days later when I had to move a post. Maybe it was to0 much/little water or the wrong sort of soil/weather.
Our hole went somewhat awry due to the s**te we were pulling out of the ground (looks like there had been a wooden post sunk there in the past close to where this post was going. So we ended up putting 5 bags and a few bricks in there. It went off impressively quickly though, I left it a few hours before i let it take the weight of the gate as a precaution but it does seem to function as it claims, which might be a first!
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