Thread: Concrete Advice

I'm no expert, but I don't think you need it, pro some mesh will hold the bits together if it cracks, con it will make the concrete pour more difficult.

Hi,
Are you casting the bolts into the plinth as you go?
Link them with a welded re-bar before casting.
I would also add a ring or two of reo in the mold as you fill it.
Cheers

Originally Posted by austastar

Hi,
Are you casting the bolts into the plinth as you go?

Cheers

No. This concrete casting is purely a spacer.

The light post will be bolted to to a piece of water pipe which will have a flange welded to it, which will be concreted into the ground

If you use dynabolts or similar that close to the edge of the plinth you are likely to break the edges away as you tighten the dynabolts. The tensile strength of concrete is somewhere around 10% of the compressive strength. I would make a template of plywood with the hole pattern drilled, then use that to hold some all-thread or long bolts whilst you weld them as a cage with some light crossbars, that will serve as reinforcing for the concrete and a secure anchor for the posts. A very simple little fabrication job that will pay off in being much easier than drilling all the holes in concrete and ensuring your plinths don't break up. We used to do the same on a much larger scale for shed footings up to 150' clear span.

From looking at your drawing and design
The post will be supported by the footing In ground
This is merely a spacer

Another option over making a seperate concrete spacer is to make your form slightly larger dimension than the pole
Bolt plate.
Do the footing with post/ plate set in place.
Now place your MDF formwork around the post and mix up a bag of durabed cementous grout - if you are using a form you can mix it to pourable consistency. Pour into the MDF form and let it set up

Grout will give a nicer surface finish - and a poured grout will seal better to the ground/ footing. I’ve painted Durabed and it takes paint better than raw
Concrete in my opinion

That’s the way I’d swing the cat ?

Linky

Lanko 20kg 701 Duragrout Structural Grouting - Bunnings Australia

Steve

Simply get taller posts to suit, Job done

Originally Posted by roverrescue

.....................Grout will give a nicer surface finish - and a poured grout will seal better to the ground/ footing. I’ve painted Durabed and it takes paint better than raw
Concrete in my opinion

That’s the way I’d swing the cat ?

Linky

Lanko 20kg 701 Duragrout Structural Grouting - Bunnings Australia

Steve

If you don't like painting you could add some concrete tint powder but colour matching might be difficult, unless you want to make it a feature in a contrasting colour.

Back to your original question, don't put reo in it. Reo needs to be at least 50mm from the edge of the concrete to stop ingress of moisture causing it to rust and consequently blowing the stucture apart. Given the concrete will shrink as it cures, there will be no load on it, therefore just go for it. If you're not experienced with concrete mixing, be very careful adding the water. as you get near the correct consistency (plastic), a tiny quantity of water too much, can cause it to be too wet. Hasten slowly.
Don.