Pour a Concrete Countertop for an Outdoor Bench

January 20, 2023

CSA Mortar Mix for Countertop Pour

I’ll be using the same mortar mix that Michael Builds uses for his countertops.

Cast your own Concrete Countertop for a Potting Bench with a Galvanized Corrugated Metal Roof — Ingredients to make concrete countertop

I’ve used this mortar mix for my thin concrete garden boxes and the legs on my garden bench. The results are very good, it mixes and pours easily and settles well with very little troweling.

Ingredients for Countertop Pour

So to pour this potting bench countertop I’ll be using 3 bags of RapidSet brand CSA Mortar Mix, using a mixing attachment for my drill and I’ll be adding a plasticizer to make it pour like water. Along with a small amount of citric acid to extend the working time. And, I’ll add a small amount of glass fiber to increase the crack resistance.

Cast your own Concrete Countertop for a Potting Bench with a Galvanized Corrugated Metal Roof — Ingredients to make concrete countertop

Preparing the Concrete Form for Casting

It’s very important to level the form along it’s length and width and support it on a sturdy workbench or sawhorses.

Cast your own Concrete Countertop for a Potting Bench with a Galvanized Corrugated Metal Roof — Level form over sawhorses

Next I need to spray it with some type of oil to keep the concrete from sticking.

Cast your own Concrete Countertop for a Potting Bench with a Galvanized Corrugated Metal Roof — Spray form with WD-40 Penetrating oil

I’ve been using vegetable cooking spray in the past but I’ll be using some WD-40 penetrating oil on this pour. This is what Michael has been using so I wanted to see if there’s any difference.

Concrete Countertop Formula I used

Here’s the proportions for the mix: A 55 pound bag of CSA Mortar Mix (25kg), 5 quarts of water (4.7L), a bag of plasticizer 2.1oz (60g), and about 2 ounces of citric acid powder (50g).

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Mix the First Concrete Batch

I measure and add the water to a 5 gallon pail.

Cast your own Concrete Countertop for a Potting Bench with a Galvanized Corrugated Metal Roof — Add measured water to bucket

Then add the citric acid and plasticizer and dissolve it.

Cast your own Concrete Countertop for a Potting Bench with a Galvanized Corrugated Metal Roof — Adding dry mix to pail

Then I add about a third of a bag of the dry mortar mix at a time.

Cast your own Concrete Countertop for a Potting Bench with a Galvanized Corrugated Metal Roof — Mixing concrete in a pail

Blending it smooth with the mixing attachment on a drill. To the last bit of dry mix I then add a small amount of glass fibre. I am following the manufacturers recommendation for the amount of fibre here.

Hand Stir to Break up Clumps

Once I have it blended I give the bucket a good stir by hand to check for any clumps stuck to the side or bottom of the pail.

Cast your own Concrete Countertop for a Potting Bench with a Galvanized Corrugated Metal Roof — Scraping pail by hand

Pour Concrete into Countertop Form

When I think I have it thoroughly mixed I pour the wet concrete into the form.

Cast your own Concrete Countertop for a Potting Bench with a Galvanized Corrugated Metal Roof — Pouring wet concrete into form

Even though I’ve added the citric acid and used cold water to extend the working time, I get to the next batch right away. Planning is key here. I have to have everything ready to go for quick, consecutive batches.

Cast your own Concrete Countertop for a Potting Bench with a Galvanized Corrugated Metal Roof — Pouring wet concrete into form

Cast your own Concrete Countertop for a Potting Bench with a Galvanized Corrugated Metal Roof — Pouring wet concrete into form

Vibrate to Settle

I vibrate the form with a reciprocating saw to bring any bubbles to the surface.

Cast your own Concrete Countertop for a Potting Bench with a Galvanized Corrugated Metal Roof — Vibrate form to setting concrete and bring up bubbles

Add a Wire Grid for Reinforcement

Once the mortar mix begins to thicken I lay in a wire grid for reinforcement.

Cast your own Concrete Countertop for a Potting Bench with a Galvanized Corrugated Metal Roof — Adding wire grid to concrete

This is a heavy gauge galvanized hog panel I bought at my livestock fencing supplier. I find small bolt cutters to work well for cutting the grid to size.

Oh NO!! RAIN!!

My nice sunny day changed unexpectedly and dark clouds with rain rolled in. I had to put together a quick improvised tent to keep the rain off the wet concrete.

Cast your own Concrete Countertop for a Potting Bench with a Galvanized Corrugated Metal Roof — Cover the wet concrete and form with makeshift tent

Max came by to keep me company for a bit.

Cast your own Concrete Countertop for a Potting Bench with a Galvanized Corrugated Metal Roof — Waiting out the rain with Max

This is kind of funny as I will need to wet the concrete once it fully solidifies, warms to the touch, and developed a white haze. Turns out that began to happen just as the rain stopped and the sun came back out. Go figure huh?

The SUN is BACK!

Cast your own Concrete Countertop for a Potting Bench with a Galvanized Corrugated Metal Roof — CSA concrete has solidified and becomes warm to the touch

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