Basic technique for Concrete Bowls:

Begins with a form. This one was packed on the top of the sand pile, But I also use some I made out of fiberglass.

 
 

The consistency of the mix is key.

Add to a wheelbarrow:
12 shovels of sand
1 shovel of type s masonry
2 shovels portland cement.

mix the sand and cement powder with a hoe.

add water, in small quantities from a bucket, mixing from one side of the dry ingredients to the other. The mix should be wet enough to move easily, but dry enough that it still holds its form.

Add a handful of fibers and mix thouroughly.

Add:
10 shovels lightweight aggregate, preferably not bone dry, not wet, though. (The stuff I'm using is little roundish red rocks - not super light, but somewhat lighter than crushed limestone)

Mix some more. Depending on how damp the aggregate was, you might need a splash of water to make it workable.

The perfect mix. It looks even a little crumbly until you get your trowel into it - then it starts to come together easily and it stays where you put it.

I trowel the rim in gently so as not to disturb the sand.

The wire ring is for reinforcement.

I trowel the up the sides about 3/4 inch thick.

Going carefully around and up to the top.

Then I do another layer about the same thickness, and I slick and adjust the form with the trowel.

For some reason I find it works better in 2 layers, but I'm not sure why.

 

This one gets a simple brushed finish, but there are all kinds of other possibilities here.


This is a bigger bowl on a fiberglass form.

I had prepared a wire reinforcement in addition to the rim wire, which I placed between the first and second layers.



Edges have been ground lightly with an abrasive cup wheel on a wildcat style grinder.

The background tile came from this image.

 

 

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