casting concrete columns

[Davey]

Hi Hazel,

I'm planning to try again, with a larger diameter pipe. ( whats the next size up?)

The problem with this is that moving from 4" to 6" dia pipe will double the weight of the column (and hence the weight of concrete required).

Just a thought - how about using a steel pipe as the rebar. A pipe, say 3/4" or 1", should give a lot of resistance to bending and it will be a lot easier to tamp the concrete down around this rather than several thinner bars.

Would be interested to hear how you get on

Good Luck

 

[TexMex]

Just a thought - how about using a steel pipe as the rebar

Scaffold tube? Might be an idea to pepper it with some holes to help key the concrete onto it.

 

[Davey]

I was thinking of MWG but there is no reason why scaffold shouldn't be used.

Adding holes is a good idea - I didn't think of that.

It should be possible to secure the rebar at the top and bottom so that this provides all the support and the concrete is just decorative. This should make the structure much safer than relying on a long column of non-structural (and possibly imperfectly cast) concrete.

 

[Hazelb]

Update on column casting:

Tried again. The results were more disapointing than the first column! I think the aggrigate I used too large and I still had difficulty compacting the concrete in the column.

So after a rethink I'll cast the columns in sections and then assemble them in to a complete column.( well it was good enough for the Romans)! I'm going to cast the sections hollow so I can fill the center with rebar and concrete to keep the structure stable.

I assume that if I cast the concrete sections and let them set, I should be able to mortar them together like bricks?

I'll post pics when its done.

 

[Thermo]

how many columns are you making?

 

[Hazelb]

only 3 about 7 foot high. I'm a slow DIY er!

 

[loublou]

the problem is that height, you'll have a job making anything 7 foot high stand.

best to buy a preformed fence post and render it over to get the look you want. you can render using soft sand with a little sharp and with a pair of rubber gloves build up from the base a bit at a time.

wet the post beforehand as it will suck up the water from the mix too fast.

you should be able to cover it in 2 or 3 goes.

sponge, trowel or lightly rub before completely dry to get a good surface.

you can also add cement colour to the mix to get a darker (black) colour or bright yellow or red, or even blue!

 

[Hazelb]

Do you mean a concrete fence post. That might help on my stability problem!