This was my second concrete project. First I made some simple rectangular counter-tops for an outdoor barbecue set-up. These can be seen in the second picture. That went pretty well so I felt prepared for something a little more challenging. I wanted to add a bar to the outdoor kitchen, but an inconveniently placed structural pillar meant that I would have to get creative with the shape. I decided on a shape that echoed a "freaky" 1950's Gibson Guitar. This would allow the post to sit in the notch of the V of the table and also the taper of the bar top would allow enough room for people to gather on either side of the bar.
Step 1: Making the Form
Working from Cheng's brilliant guidebook "Concrete Countertops" I made the form using melamine board. For safety I opted for curved ends, rather than the sharp angles of the Gibson. This initially posed a problem, but I was able to get the curves that I wanted by using different diameters of PVC pipe. I cut this to the correct angle and held it in place with backing blocks of melamine. Then plasticine was used to protect the screw heads from concrete and facilitate dismantling the form. All seams were caulked with black silicone (easier to see than white) and smoothed to the rounded profile that I wanted for the top edges.
Over the years, living on a boat, my wife had accumulated lots of interesting beach glass, which sat unnoticed in a jar in the kitchen. This project would allow us to show it off! I was looking for a look that emulated the shoreline - where beach glass is found - with the sea on one side of the table and sand on the other. Since we live on the water the "sea" side would naturally face the water.
I drew a wavy line to guide the "shoreline" and sprinkled beach glass along the line.
Step 2: Concrete, Fiber Feathers and Colorant
Next it was off to the hardware store for supplies. I strongly recommend reading Cheng's book as the formulation of the mix is pretty important and some of the additives needed were not easily found. We were able to buy the colorant online, and a friend in the business hooked us up with fiber and water reducer. All of these products are also available from Cheng's website.
The next decision was where to pour the concrete. I was doing this job solo, working with two different colors of concrete and the job site was down two flights of stairs from where I planned to mix the concrete. These logistics had me concerned that I would not have time to manually mix the needed amount of concrete, so I found a well used mixer on Craigslist for $150. (After the job was finished I later sold it on CL for $160). The finished table would be too heavy for me to move or lift solo, so I set up the form as close to the installation location as possible. I bought a bunch of buckets to transport the concrete mix down the stairs.
Mix components were calculated based on the working capacity of the mixer and colorant in particular had to be carefully measured to ensure each small batch was consistent in color.
Step 3: Mixing and Pouring
These pictures show me packing the concrete mix in, trying to fill all the corners of the mold/form while not displacing the rebar mesh. In retrospect I think my mix was a little stiff, and even after an hour or so of vibrating the mold with an orbital sander I was still getting bubbles and had a number of small voids in the finished table. I was able to fill these holes with a skim coat of cement before polishing.
Step 4: Finishing/Polishing
My only significant tool investment for this project was a Makita Stone Polisher and diamond polishing pads. The first picture shows the ladder frame that I built to support the bar top with the completed bar top still in the mold in the background. The 6" X 8" posts supporting the bar top are through-bolted to the deck joists below the deck. The next picture shows the bar top straight out of the mold and before any polishing. I installed the bar top before polishing since it would be at the perfect height for working. I gradually worked my way through the progressively finer pads and worked most heavily on the water/sand interface where I revealed the beach glass. Finally I sealed the surface with several coats of sealer.
Step 5: Before and After
This view is looking down on the project from the top floor of the house. The first picture shows the original deck just after an old fiberglass spa had been removed from the 25 year old cedar decking. As can be seen I expanded the deck area and replaced the cedar with Ipe decking. The outdoor kitchen counter (three pieces) was my first attempt at concrete work and was left natural color.