Sunday, March 28, 2010

Concrete Planter Project (4. Finished)

Concrete ends with recycled glass tile scraps coated with soy-based epoxy. Scrap Ipe wood middle from a local rainscreen manufacture sealed with soybean oil.
Cutout detail for mounting the wood.

Friday, March 19, 2010

Concrete Planter Project (3. Finishing)

I stripped the forms two days after placing. When I strip the forms at 1 day, even with high strength concrete, the finish isn't as good as at 2 days. It took about an hour to grind through 50, 100, 200, and 400 grits. Since these are going outside I didn't feel the need to go any smoother.
Straight out of the forms, pretty grey and boring.
The glass tile pieces after grinding.
They got sealed with the soy epoxy I used on the fiber optic buffet top. It is semi-penetrating and provides a nice wet look. The triangle-shaped holes are handles.
I am waiting on the hardware to put everything together.

Monday, March 15, 2010

Concrete Planter Project (2. Concrete)

The concrete planter ends are progressing. All the joints got filled with silicone and a glass tile design was put into the front.
The mix was a quikrete 5000 base with 50% latex modifier. I used water reducer to bring the w/c to 0.4. It also had some fibers and a little bit of black pigment to make it a little darker. Here is my simple setup, complete with the bathroom scale and cat litter buckets.
I use two types of fibers. The left is a fibrillated (think fish net) polypropylene. The right is a cellulose fiber let over from making furnace filters and dusters. The little packets break up into individual fibers. Since I don't use any reinforcing steel, these will keep any cracks small. These planters won't ever be in tension so I probably don't need any fibers.
With the high range water reducer the concrete has the consistency of stiff honey. A little hand vibration and it flows. It needed to be flowable to get under the mounting lip for the wood boards.

Wednesday, March 10, 2010

Concrete Planter Project (1. Mold Making)

The recent warmer weather has a few projects starting around the house. I am building raised beds for the garden out of ipe wood and have some extra material. I have enough extra to build a couple concrete and ipe planters. Ipe is a very hard, very dense tropical wood that makes great patio furniture.
Mold making for concrete countertops/projects has evolved recently (past 10 years). Cheng started using particle board and laminate then switched to melamine. Every project used fresh mold materials and used lots of drywall screws to keep things from moving. Lately Cheng has switched to foam boards secured with tape. Many other mold builders have switched to foam board and thick vinyl tape for lining the molds. Others have switched to fiberglass or flexible urethane molds. It turns out that most of the older style molds were over-built and wasted too much material. I have built a couple molds lately with little to no screws.
Here is one of the end molds for the concrete planter. It is basically square with knockouts to secure the wood pieces and a handle indentation. Other than a few leftover screws holding together the bottom knockout, there aren't any in this mold.
For the sides I cut the bottom melamine used for the fiber optic topic and sealed the ends with polyurethane. The mold pieces are held down with silicone caulk. Brown was on sale. The knockouts are just leftover plywood coated with polyurethane.
Instead of screwing the braces into the bottom piece and sides, they are secured with caulk too.
A couple minutes later the mold is complete. I let the caulk dry and then fill the seams. After casting the concrete everything comes apart and cleans up easily.
These ends are 4 inches tall and will be held just fine with caulk. The fireplace mold was secured with caulk because I didn't want to drill into my floor. That was 12 inches tall and didn't move at all. Using this technique I can reused my mold pieces and the bottom won't have a scratch.

Monday, March 1, 2010

It's Winter, blah!

I haven't posted in a while because, well it's winter and I haven't done anything. Spring is getting close and thoughts of drinking on the patio are surfacing. One of the first projects for the new year is a table for the patio. I picked up this tulip base last year. It is going to get a green concrete top. I am toying with the idea of embedding steel and letting it rust through the surface.