I need to put in posts to stop tresspassers in large trucks.
The plan is to use 6-ft lengths of 6-inch sch.40 steel pipe,
with 2-1/2 feet underground. I will dig 8-inch diameter holes.
I have a 3-1/2 cu.ft. mixer for concrete.
My questions concern the concrete. I've read that type III cement
will cure faster. Is that the appropriate type for this application?
What size & type of aggregate is best? Are there any admixes that will
give it faster cure and high strength?
Any ideas on the whole approach are welcome. These bollards will
possibly be subject to bashing, winching upward, and who knows what
else. The concrete will have to have good strength within 1 or 2 days.
Thanks in advance for your suggestions.
The concrete that you use will make little difference in the
strength that you are looking for. An accelerant can be added
to your mix to make it cure a bit faster, but I wouldn't even
bother with that. It will be strong enough, fast enough for
your needs. I would consider making the hole diameter a bit
larger, say 12" in diameter. That would increase the strength
of the whole apparatus a bit more than a different type of
I would suggest using sched. 80 or even 120 pipe if you can
get it. That would certainly increase the strength of your
yeah, just get regular concrete
please post pics of damages after people run into your posts
An 8" hole only leaves a 2" layer of concrete around the pipe, kinda' thin
in my opinion. I'd go at least 12". I'd weld some pins or flare out the
bottom of the pipe somehow so that if the impact breaks the concrete bond to
the pipe and loosens the surrounding concrete they can't be pulled up out of
the hole. Since this seems like a permanent deal you might also put a
anti-vehicle trench in front of the pipes.
Thanks for all the ideas.
I'll forget about the fancy concrete.
Good advice on the 12" holes.
Pins are a good idea but do I really need to weld them?
I'm thinking just drill thru both pipe walls and wire them in place.
Robert, I'll price the heavier pipe. I know the price will make me cry.
I'm going to visit the salvage yards and hope something turns up.
Actually just had another thought about this. A few months ago I had to
remove some fence posts that are almost exactly the same size as your steel
posts and buried as deep. Took my small loader (Allmand 325) and pushed on
the top of the post about 12" then pulled it back 24". Moved over to a
different angle and repeated. Backed up loader, went to post, lifted out of
hole by hand.
Bottom line - Depending on the soil, even a 12" hole might not be enough to
keep a truck from simply pushing the post over or loosening it up enough in
the hole. You might need to make sure your concrete base has a couple
hundred pounds of weight.
Welding the pins wouldn't be necessary, just make sure they do the job. You
might check the salvage yard for pieces of railroad rail. That's what was
used at an ammo dump where I was stationed once.
You don't need heavy wall pipe, you could build it as you described with
solid bar and it would still be easily removed. You need foundation,
substantial foundation otherwise all else is a waste of