Right ratio for making bowls with concrete?

I recently got someone to buy me concrete mix - I asked for ready mix as I've seen people suggesting Quikrete, but I ended up with 2 bags - one with the cement and one with the gravel and sand.

Now, I want to make smallish bowls for outdoor use over the weekend (bird baths, small plantholders, etc.), but I'm not sure what my ratio must be for the sand / cement or sand / cement and gravel mix (and I'm not planning on buying another product). I've read that people can mix only the sand and cement for a smooth finish, but will this be strong enough? The gravel I have is quite large, and it might make the finish too chunky when the concrete is dry.

I'm also planning on not using bowls or containers as molds - I want to smooth it out on the outside or inside of a bowl by hand with a trowel or something similar. Will I be able to make this work? I want to make small bowls, so I don't need to mix large amounts at once. I have never worked with concrete before, so I want to start out with small items anyway just to get the hang of things.

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Leave the gravel out.

You will need some sort of mold to poor the cement into. You won't be able to get a mixture that can hold it shape and be molded like clay.

You'll need to play around with the mix ration to see what works best for you and gives you the desired finish.
Nocturmia (author)  mpilchfamily3 years ago
Thanks for the help - will it still be relatively strong without the sand though?
No you need the sand. You don't need the gravel. The sand acts as a binder. You can substitute sand for a finer and more robust material like fiberglass to get a smoother finish and added strength.
http://makezine.com/2012/04/11/how-to-mix-and-mold-gfrc/
Nocturmia (author)  mpilchfamily3 years ago
Thanks again, I'll play around tomorrow :)
rickharris3 years ago
start with sand 6:1 cement and work from there.

As said you need a mould - 2 containers, 1 to hold the concrete and the other to give the inner shape - You may also need to embed some chicken wire to give it strength - Concrete has very good compressive strength but poor shear (bending) and tensile strength (pulling) - that's why in construction they put steel bars in the concrete.
Nocturmia (author)  rickharris3 years ago
Thanks for the info. I'll definitely try chicken wire too