Lightweight Concrete Stackable Garden Beds
Here’s the blog post for the YouTube Video on making lightweight stackable garden panels for a raised bed using one of our ABS plastic molds.
Casting the Concrete Raised Garden Bed Panels
Lightweight Concrete Stackable Garden Beds
Here is the weight of 2 cured panels made from regular concrete: 36″ – 50lbs, 24″ – 33lbs.
See the Youtube Video
Summary of this blog post
Make stackable lightweight concrete panels that link together to make long-lasting rot-proof garden beds. In this episode I mix and pour two lightweight concrete blends and cast garden box panels that can be stacked to create deep garden beds. The panels link together at right angles to make a square or rectangular raised garden beds. They can also be linked end-to-end to lengthen the garden box. The two lightweight concrete blends replace the gravel in a portland cement based concrete with perlite or vermiculite. Perlite and vermiculite are minerals that are naturally light and abundant and make an excellent alternative to heavier gravel. The panels are poured in plastic ABS vacuum formed molds with removable pipes to form holes in each end.
(this post is based on the transcript of the youtube video.
Introduction to Lightweight Concrete
On this episode I’ll be making some coloured, lightweight concrete in these new plastic forms and then stacking them to make a deeper and taller raised garden bed.
For the lightweight blends I’ll be replacing the gravel in a portland cement based concrete with first perlite, and then vermiculite. In the perlite blend I will add a red concrete color and in the vermiculite I’ll try the black and see how they look.
Mixing concrete creates a bit of dust so, I will mix my ingredients outside, then bring the wet mix into the shop to fill the molds. This way I can maintain the ideal temperature of 70 degrees, so the concrete hardens at a predicable rate.
Later, when we get to stacking these panels, I’ll talk about some ways of making that easier. With the panels from the plastic forms there’s a draft angle on the edges that affects how they mate to each other. It’s just something we have to think about when stacking them.
Also, I’ll be prepping my molds in a new way that’s different, and I think better, than I was in the first plastic forms video.
Lightweight concrete is not as strong as sand and gravel based concrete, so I like to add some wire reinforcement to my panels. I add a wire wrap around the pipes and a wire grid down the middle. This is just some extra insurance and it doesn’t take long (or cost much more) to wrap the wire and cut the grid. The wire and grid are available at most building supply stores.
Alright, let’s get started.
Prepping Your Workspace for Pouring Lightweight Concrete
I always work on a bench that is level in both directions so the forms fill evenly. And I can check that with a spirit level across the table, and then lengthwise.
The floor of my shop is slightly sloped so I add a few wood shims under the legs of my bench.
Wire Reinforcement for the Lightweight Concrete Panels
I use 12 gauge galvanized fencing wire to reinforce the concrete where it’s the thinest. And that’s around the hole formed by the pipes on either end of the panel.
To make these wire wraps I use wire cutters, pliers, and a short length of plumbing pipe that’s 7″ long and 7/8″ inches in diameter.
I first cut a piece of the fence wire approximately 24″ long. Use caution when cutting this wire as the ends will be sharp and the roll end can spring back and possible cause injury.
I wrap this wire around the pipe 4 times keeping it between the two black reference marks I added that are spaced 3-1/2″ apart. When I wrap it I go slightly beyond 4 rounds then back it off to open up the spring (if you will) and line up the two ends.
Then with pliers I loop back these cut ends.
And this is how it will sit in the mold before adding the wet concrete mix.
