2016 DCC Award Winner
Aruba Residence, Tom Ralston Concrete
First Place: Cast-in-place – Special Finishes / Over 5000 SF
The owner’s motif for the “beach home” would be modern architecture; 8,000 SF with an additional 8,000 SF of concrete for the exterior work. The scope of the concrete work included upper floors, lower floors, cantilever stairs and a pool deck; as well as side and front entries.
The concrete work was laden with an array of challenges. Distance was the first factor: we are based in California and this project is south of Cuba which is over 4,000 miles. The logistics of getting specialty supplies to the site for an architectural pour was complicated. We needed to transport special colors to blend, special tools and work out travel for our manpower. The upper and lower floors for this new home each had separate blended colors, as did the pool deck and the front and side entries (4-different blends in all). We had to crate all of our specialty tools, jointers, special concrete saws, finishing tools, etc. We made at least 15 samples for the owner, and since he was so busy we had to mail small pieces to Berkeley from Santa Cruz. It took 7 crack finishers plus laborers from a Dutch Construction Company to pour the concrete.
Blending Colors: We decided to go with Brickform Color because they were extremely accommodating and excited with this project. We have had problems with color hardener consistencies with various manufacturers in the past and Brickform assured us that he would set out all of the color hardeners that we needed that were made from the same batches. Over 300 pails of color were eventually shipped from Brickform to Aruba from Florida. Blending 4-different blends of colors and keeping them straight was tricky and required tight quality control for the mixing and clear labeling. So it was one of our first tasks was blending all of these 300 pails of color hardeners and separating them into 4-different categories.
Mix Design: Prior to the trip I worked extensively with the Director of Concrete Products at the Granite Rock Concrete headquarters in Northern California. We did batch tests and as many as 20 samples with various mix designs and blending various colors and textures before we flew to Aruba. We did our best and were confident that the 5000 PSI mix design we had could perform well and withstand the fierce elements in Aruba. We didn’t add any water to the concrete when it arrived, only special additives. I insisted on pouring a ¾” mix design which required using a boom pump throughout the house. A year later we could only find 4-hairline cracks in all of the concrete we poured.
Pouring Concrete: The wind and sun are daily occurrences in Aruba where wind gusts average 28 knots and temperatures hover around 80 degrees. Over 18 pours were made so we could assure that the finishes were perfect. Because we had to fight the elements many of our pours were made in the dark when it was cool; or as we liked to say at “zero dark thirty.”
Special Finishes: We used an acid sand wash on the exterior and a Monet finish on the inside floors. The sand wash was produced by using an acid/water solution. The Monet finish produces an acid stain like variegation in the colored floors which require a special technique. We also used a jointing tool and system developed in house to mimic saw cuts without using a saw. This allowed us to make very clean, thin lines without the usual spalling
Hydration: There were not many expansion joints in the floors as per the design, so we had to take extra precautions against cracking. Due to the wind and sun, we hydrated the slab 15-20 times per day.
Sealing: All of the concrete was sealed with an impregnating sealer to give it more of a natural and organic look.