Custom concrete pavers II

Here's something I did back on the 23rd.

In Forms for custom concrete pavers I showed how I make the forms for the pavers that I use in my yard. Here's a bit more detail on the moments before a pour.

I assembled the paver form the night before, and it took about 16 H for the silicone caulking to dry to a state where I thought it was OK to pour. I wasn't 100% right on that - it could have gone longer. I used white, because that's what I had on hand, but my preference is for black since it's easier to see against the white of the form. My goal was to make a water tight tub for the concrete to set up in and then add a few artistic touches that make this a truly custom job.

I've added plenty of leaves before, mostly from the Magnolia in my back yard. Normally I'll press a leaf down into carpenter's wood glue with a board and a brick. This time I used Western Redbud leaves which are more flexible than the Magnolia and also, because it's a native tree, more meaningful to me. I set them in a bed of the same silicone adhesive that I used on all corners, but didn't press them down other than with my fingers to bed them in. I don't know if this feature will turn out. We'll see.

I also added a hole in the paver to let me grow a small plant or maybe just to break it up visually. I could always just put polished rocks in it. The form for the hole was cut down from a large PVC coupling using a hacksaw, then slit up the side. The side slit is intended to let it compress and come out easily, but I filled the slit with caulking because I was out of packing tape. What I really needed was a wider side slit with tape over it. I anchored it into the pouring table with a piece of wood and two screws and gave it the same waterproofing treatment that the rest of the from received.

Here's the completed form with some tools of the trade. On the right side of the form, I've aligned the edge with the edge of the fluorescent light cover which will give me the surface texture. At left, the little triangular braces hang out over it a bit. The braces are Maple, a hardwood.

The Christmas box in the picture holds my drill bits. The bottom of the mold is fragile - I suggest drilling first before trying to insert screws.

The top of the form edges received a layer of clear packing tape, until I ran out. This prevents water intrusion which can really degrade the form. Cheng seems a bit anal about this, but that's why he makes beautiful pieces. My previous experience says that it's not critical, particularly for garden pavers. Still, the form will keep its life a bit longer if I use it.

I level out the form in both axes using some left over shims and spacers placed under the table.

I add color (this time I was a bit bolder than previous attempts and added about half of the colorant). I also add about a fist full of polypropylene fibers (at left below) to strengthen the concrete.

Below, the concrete, mixed and ready to shovel into the form. Those Atlas gloves are invaluable. I also use a NEMA-approved dust mask when pouring the concrete out of the sacks - the dust is mighty fine and quite alkaline. I use a special hoe with some holes in it made for mixing concrete, but I'm sure a plain old hoe would be fine.

The volume of concrete shown comes from two 60 pound sacks of Quickcrete 5000 and it fills the form nearly to the top. If I were pouring a countertop I might be a bit more anal about getting right up to the top of the form.

I have always found that the concrete takes nearly twice as much water as the bags say you need. I used about 1.8 gallons for this batch, and the bags say that 0.5 per bag is sufficient. They also say not to exceed twice the recommended amount, so I'm OK. Add some of that water to the empty mix container before you add the dry concrete so that the bottom gets wet. Mixing ~130 pounds of concrete with that hoe is a work out!

1 comment:

  1. Thanks so much for sharing this. I had to get some concrete pavers to renovate my backyard as well because it was long overdue for a fixing. Now that the weather is nice, I can finally enjoy everything they've done.