Lightweight Concrete Garden Boxes – Pt 3.5 Perlite, Portland & CSA Cement

Add Reinforcement to the Lightweight Concrete Panel

This galvanized wire mesh is cut from a large hog panel fence I bought from my local farm supply store. I used small bolt cutters to cut a piece of this heavy 4 gauge panel to fit the form.

adding hog panel reinforcement grid to wet perlite concrete
Hog panel wire grid adds tensile strength to concrete panel

Then I topped up the rest of this and vibrated it some more. I use a trowel to smooth the surface.

trowel smooth the wet concrete in the molds
Little smoothing of the surface with a trowel

I liked the consistency of this first blend so, I decided to make another batch with the same proportions as the first. But this time I’d add some glass fibre for more reinforcement.

adding fibre to perlite concrete mix
Glass fibre added to wet mix

Perlite is very light and it’s easy to mix in a wheelbarrow. And for these tests I like this method as I can really see how it’s blending. And how much water I need without over doing it.

filling the forms with wet concrete
Lightweight Concrete Perlite Portland CSA Garden Panels

This second batch went well. Like the first, half fill the form, vibrate the mix to settle it and bring bubbles to the surface, add the wire grid, then top up, settle, and finish with a trowel. And I’ll round off the sides when it sets up.

finishing the concrete with an edger
Edging tool rounds over sides

It was the end of the day so I covered the forms with plastic and left them to harden.

The next morning I set up to make two more batches. This time in the 36 inch forms.

Cement Color

liquid cement color
Red cement color

This third batch used the same proportions as the first two but, for this one I’ll add some red colour. I add two ounces to the mix in the wheelbarrow. And I’ll add some glass fibre again.

cement color added to perlite concrete mix an a wheelbarrow
Diluted red dye added to wet sand and perlite

I start as before, blending the perlite and sand. I then dilute the red colour in water and add it to the wheelbarrow. And wow, it was very red!

shovelling wet perlite concrete into forms
Wet red-dyed perlite concrete added to form

Then I add some fibre. And finally the portland cement. There were a few chunks of portland so I broke them up by hand. Now it’s a matter of slowly adding water for just the right consistency.

Wire Mesh for Strength

adding hog panel reinforcement grid to wet perlite concrete
Wire grid laid in

You can see the sheen of the vegetable oil spray I use on the forms before filling them. Pam cooking spray works very well. I cover the wires that wrap around the pipes to keep the oil off them while spraying.

trowel smooth the wet concrete in the moulds

And like before, I filled the forms half away, settled it a bit with the reciprocating saw, add the mesh, and then top it up. And smooth any bubbles with a trowel.
The red colour looked to be pretty uniform throughout the mix. I think the key is to add it to water first. And to add it early in the blending.
I was getting a pretty good feeling that the perlite blend would be a good lightweight alternative, similar to the vermiculite blend from Part 3 of the series.
So, for the 4th form I decided to change things up with the proportions AND the type of cement.

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