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

Make your own Lightweight Concrete Garden Boxes! This is PART 3.5, showing options to make your garden boxes from Perlite-based concrete.  You can build these forms and precast your own 48″, 36″, or 24″ reinforced lightweight concrete panels that link together to make long lasting and durable concrete garden boxes.

Here is the weight of 3 cured panels made from regular concrete: . 48″ – 69lbs, 36″ – 50lbs, 24″ – 33lbs.

See the Youtube Video and download the Plans.

Background for the Cast Lightweight Concrete Garden Box Project – PART 3.5

make Perlite Concrete Garden Boxes PART 3.5 - Lightweight Perlite with CSA and Portland Cement
Watch this video on YouTube.

Hi it’s Kent from MAN about TOOLS and this is a follow up video to Part 3 of my series of making garden box panels from lightweight concrete. These reinforced concrete panels link together to make long lasting rot proof garden boxes.

talking about the perlite concrete test
Lightweight Concrete Perlite Portland CSA Garden Panels

In part three I experimented with some concrete mixes looking for a good alternative to gravel-based concrete that was light and durable. In that part I looked at three blends. As that was more than enough to cover in one video. The vermiculite blend was my favourite but, I also wanted to try perlite as an aggregate.

So that’s the focus of this video. And to also add some colour to the concrete.

perlite is a very light rock and makes a great additive for concrete

Perlite is a hard, highly porous material made by super-heating volcanic glass. Some viewers thought that perlite would be superior to vermiculite as perlite does not absorb as much water.

I’ll show the mixing, pouring, and unmolding, then look at the weight and durability results as compared to regular gravel-based concrete.

If you haven’t seen part 1 or part 2 of this series then you might get more from this video if you watch them first.

I’ll be using the forms I built in part 2 of the series.

Lightweight Concrete Ingredients

Lightweight Perlite Concrete Ingredients
Lightweight Perlite Concrete Ingredients

This lightweight concrete blend is made from portland cement, perlite, and sand.

Glass Fiber for concrete
Glass Fiber for concrete

To some of the batches I’ll add a small amount of glass fibre for extra reinforcement.

You add about one pound of this fiber per cubic yard of concrete. So when I calculated how much I needed per batch it came down to a third of an ounce per 48 inch panel.

Lightweight Concrete Mix with Perlite- 1st Test

Ingredients I\'ll use to make Lightweight Perlite Concrete
Perlite Concrete Formula

Here’s the proportions I used for the first attempt at perlite concrete: one part portland cement, two parts perlite, and one part sand. These proportions are by volume.

I didn’t realize how dusty the perlite would be so I was glad I was working outside. A mask would have been better. And I did wear one later on.

adding water to the dry concrete ingredients
Mixing Perlite concrete in a wheelbarrow

I add the perlite and sand to my wheelbarrow first. And add a little water to wet the mix.

adding dry portland cement to the wheelbarrow to make the perlite concrete
Adding portland cement

Once it’s well blended, I add the Portland cement. And continue to add water a little at a time.

When I saw that the mix ratio was looking good and the wet perlite concrete blended smoothly, I added half as much more of the ingredients, in the same proportions, to increase the batch size so I’d have enough to fill my 48 inch form.

Filling the Form

filling the forms with wet concrete
Shovelling wet perlite concrete into a form

I add a few shovel fulls to the form and push the perlite mix around the pipes with a small trowel.

I used a reciprocating saw, without the blade, to vibrate the form and settle the concrete mix. Then I laid in a section of reinforcing wire mesh.

vibrating wet concrete mix to settle it
Vibrating form with a reciprocating saw
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