Concrete as art- Need help

Bit o’ backstory. Last year, my SO turned 50 and as a birthday surprise, I took him down for a tour of Frank Lloyd Wright’s Taliesin. Since then, my interest in turning our post-Victorian/pre-Prairie house into a full on Prairie style house has been in full swing. After making some furniture and household things in a Wrightian style, I’ve changed my focus to the outside. A couple weeks ago, I made some sidewalk lights in the style of his Hillside Lamp.
This past weekend, I decided to delve into the world of concrete and try and make some paver stones to start with. Let me emphasize that word: TRY. Based on the culmination of knowledge I could discern from the web I needed the following:

  1. Concrete (preferably the stuff without the big chunks, so I got the Quikrete with sand

  2. Water

  3. Mixing bucket

  4. Not needed-but I got the mixing paddle for the drill which worked well

  5. Mask and gloves

  6. A mold of some type. I made the mold out of oak plywood. A 5 sided box to begin with and a design at the bottom with pieces of plywood glued in the shape of FLW’s Lake Geneva Tulip pattern. I then coated that with a sealer 5 times.

  7. Pam to release the concrete
    Here’s where I probably went wrong.

  8. Concrete and water ratio off. I think I used too much water based on the fact that 24 hours later and it’s still drying. It’s about 2" thick though.

  9. The mold. First off, I should have drilled the pieces together. I didn’t want it too permanent should the concrete get stuck. But when I tried to tap the bubbles out of the mold, the sides began to collapse and the concrete started to leak out of the corners. A couple wood clamps later and the shape was returned however.

  10. This morning, 24 hours later, I removed the clamps and while the top was dry the sides were still wet and the concrete still cleaved to the bottom.

  11. Pam not strong enough or should have used different type of lubricant to release.

  12. Maybe making a mold using wood was a dumb idea altogether, maybe a latex mold would be useful?

So before I even attempt to go on to bigger projects (like theRobie House planter which I really want), what are some tips, ideas, basic info on how to do this? Like how to make a proper mold? What type of concrete to use?

Advice from an amateur:

Clearly too much water in your mix, it takes less than you think and you have to add it in slowly while mixing. Use a fine spray attachment on your garden hose to keep from adding too much at once. I’ve never used a drill mixer for concrete but it sounds like it would tempt you to add too much water to get it to work. A concrete hoe in one of those flattish poly pans works well and they don’t cost too much. I put the pan on top of boards on blocks to get it up in the air to save my back when I shovel it out later. A wheelbarrow works just as well.

I have some experience with this sort of thing. We made concrete countertops a few years ago, and I think you’d get some good advice researching countertops.This website is good. Check out their “small projects” page, too.

We made the forms out of melamine board, like the use for the insides of cabinets. It’s fairly inexpensive. They also make form-release stuff, although I’ve never used it.

Concrete should kind of hold its shape when it’s mixed to the right consistency. This is known as “slump.” I’ve never been bothered to do an actual slump test, but when mixing with a shovel, when you turn over a shovel-full, it shouldn’t be soupy, it should be formable. You’ll want it a little wetter for a project like yours, because you’ll need it to fill in around the intricacies of the mold, but still not soup.

Typing this is making me want to build something out of concrete, which is saying something, as we are in the finishing stages of building a DIY ICF house. I thought I’d never want to look at concrete again, after pumping about 100 yards of the stuff this winter. :slight_smile:

concrete doesn’t dry out, it cures. the water becomes part of the hard stuff you end up with.

you don’t need tons of water. a mound of it should settle some but still stay a mound. with you’re moving it with moderate pressure then you could fill a mold.

you will waste much cement if you don’t use some stones. the smooth cement will come to the surface if you want that and don’t add too much stone.

The concrete should be as thick as you can make it without any dry ingredients visible- the amount of water that it takes to go from “correct” to “too much” is surprisingly small. I always start with 75% of the recommend amount, and then add only small amounts as I mix.

It should require tamping to fill your mold- if it fills to the corners without “patting” the top, it’s too liquid, and will be very weak.

I was watching the process they used to make commercial pavers once and was surprised that they used very small amounts of water. They would cure and come out of the form in just minutes and be harder than standard concrete slabs.

I am thinking of starting a paver project myself here soon.