Garden Box Plans from Concrete – PART 4 CSA Cement


I’m using CAS mortar mix for these thinner forms. In North America, the Rapid Set brand can be found at Home Depot.

Mortar mix and plasticizer
CSA Mortar mix and plasticizer

To make the concrete flow and pour like water I’ll be using a plasticizer. One small bag per batch. This mortar mix sets up very fast, so to give me more time, and to slow this down,

glass fiber will add strength to the CSA concrete
Glass fibers to reinforce concrete

I’m going to add a small amount of Citric Acid powder. This powder can be found in most health food stores or a grocery store in the canning section. In addition I’ll add a third of an ounce of glass fibre. This is the manufacturers recommended amount.
Here’s the proportions for the mix: A 55 pound bag of CSA Mortar Mix, 5 quarts of water, a bag of plasticizer, and about 2 ounces of citric acid powder. These garden box plans were specifically designed for this type of concrete.

CSA Concrete Formula

CSA Concrete formula
CSA Concrete Garden Box formula

I add the water to my mixing pail and dissolve the citric acid powder. Then I add the plasticizer and dissolve it too. Then I add about a third of the bag of mortar mix and some glass fibre. I’ll blend this until smooth, adding more dry mortar mix slowly.

mixing concrete in a pail or bucket
Adding dry CSA mortar mix to pail

One batch will fill two 36″ forms or a 48″ and a 24″. I fill each form with the concrete mix. And vibrate the forms with a recip saw (without a blade) to bring any bubbles to the surface. When the concrete begins to thicken I lay in the galvanized wire grid and push it into the centre with a trowel.

pouring the CSA Concrete mix into the forms
Pouring CSA concrete into garden box panel forms

I mixed one final batch to fill the last 48 and 24 inch forms. Laying in wire grid as it solidifies.

pushing the wire mesh into the form while the CSA mortar mix is still wet
Pushing wire grid into thickening concrete with trowel

I wet the forms when the concrete hardens and begins to dry on the surface, and a white spotty haze forms. I do this water curing for about an hour.

Water curing the CSA Concrete once solidified
Water curing concrete

Strip the Forms

After an hour, the concrete can be removed from the forms.

plastic pipe firmly embedded in the concrete
Form side removed showing pipe embedded in concrete panel

Now the screws can be removed and I can gently pull off the sides. And then each end. And I can free the panel from the base with a little help from a paint scraper. And here’s a 48″ panel coming out of the form.

(Disclaimer: As an Amazon Associate I earn from qualifying purchases. Thank you for helping to support my content this way. )

The final CSA concrete garden box casting
CSA concrete garden box panel and form base

The newly cast panels should now be at half their full strength. They will reach near maximum strength in about 4 weeks if kept wet. The latex caulk can be easily scraped off with a putty knife and the form parts wiped clean with a rag. I was happy with these new garden box plans. The csa concrete is very smooth and casts very well.

the panels are 40 percent lighter than portland-based sand and gravel concrete
Thin CSA panel is 40% lighter than portland version

So I really like how these concrete panels came out of the forms. It’s the nicest concrete I think I’ve ever poured. The original portland based concrete forms are about 50 pounds for a 36″ panel. These new panels are only 30 pounds. So pretty significant savings in weight and concrete

cutting metal corner pins
Cutting electrical fence post for panel pins

I cut electrical fence posts into one foot lengths with my reciprocating saw. A hacksaw or a cutoff blade in an angle grinder would work too. And I painted these bars with some rust paint.

spray paining rusted metal corner pins
Spraying pins with rust paint
Shopping Cart
Scroll to Top