Concrete Posts.

[forgeblast]

I really like the jig you made. Its a good design that lets you reload it quickly. Very nice job.

 

[RobertBrown]

How did the posts come out Loyd?

 

[RDrancher]

I use a Corner Cat vibrating sander for a cheap concrete vibrator when pouring counter tops in place or casting into forms. Just hold the sander by the end and let the plastic housing that you normally hold onto vibrate against the form.

 

[Lloyd_E]

Robert,

Will be removing from forms tomorrow...


lloyd

 

[Lloyd_E]

Well... this is on going. Some of the posts worked... broke a few trying to get out of form.

1/ redesign form
2/ use more oil
3/ look at mix

The mix I used was a combo of sand/aggregate from concrete plant. Just add portland and water. The ratio was 3:1. I know I added a bit more concrete. The water and final mix gave me a very thick mud - less water makes a stronger mix. Once in the mould a little bit of water pooled on the surface.

I think the aggregate was too large for what I am trying to do - roughly up to 3/4" stone.

On another note: I have a small concrete garden table (18"x24"x2.5" top) which sits on cast concrete legs - think saw horse. It has small (pea gravel or less in size) gravel in it. So, looking at that I think I will rework things and try again...

I did find a site
selling wood posts mounted to a 60" concrete post via a galvanized u-bracket for just under a $100 bucks... this makes it worth trying!!!

 

[MikeD74T]

Lloyd, Use less water in your mix. Stone is where the strength is, most stone is stronger than cement. Remove forms from posts, not posts from forms. Did you wet cure?? Steam cure is even better. Do a search for ferro-cement, wealth of info there, especially on concrete/reinforcement ratios. MikeD74T

 

[Egon]

Consider using 2 mill plastic to line the form with. Cheap and it should separate. Also cosider using slotted end boards to hold the post side pieces in place. Have the slots just a little oversized so the form pieces can come out easily.

Check with a local concrete plant for some proper sizes and graded aggregate as well as a proper cement /water mix.

In industry many items like you are doing are almost a dry mix, formed under pressure and cured in a humidity/ temperature controled environment.

Note: 40 year old data may not be correct any more.

 

[MikeD74T]

Egon, Which "40 year old data" are you refering to? MikeD74T

 

[Egon]

Re: Concrete Posts.
Egon, Which "40 year old data" are you refering to? MikeD74T


I have not kept up to date and as such may be well out of date.

 

[bearhawk]

I would have thought that the form would have to be removed from the post, not remove the post from the form. But I wasn't sure enough to comment.

If you built the form so it could be taken apart, say remove the ends, and then the first part of the side form. Remove the first post. Then remove the next form separator, and continue till the base was empty.