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2016WinterShotcreteEMag

Fig. 3: Some of the intricate plumbing and steel work are prone to efflorescing on the exterior of the shell, which can be quite unsightly and cause problems with the exterior cladding. In this situation, not only did we need to hold water in but we also needed to shoot walls 26 in. (0.66 m) thick standing 5 ft (1.5 m) high. To mitigate both the efflorescing problem and to aid with the rapid buildout, we proposed to the pool designer, Brian Van Bower with Aquatic Consultants, the use of silica fume as a supplemental cementitious additive in the dry-mix shotcrete material. He agreed and conferred with the Architect, Steven Price, and with Bill Drakeley, who served as our shotcrete inspector on the job. Both agreed with the addition. Silica fume has long been used in the infrastructure and tunneling industries and has proven to reduce efflorescence, reduce rebound in the shotcrete application, and increase the ability to build out rapidly. Silica fume has also been laboratory-tested and proven to reduce permeability in concrete. The volumetric batch trucks that Revolution Gunite uses are designed to be able to add silica fume as an additive before the mix bowl. After careful calibration of the truck for the correct dosage, we used the silica fume in all parts of the pool except the floor, where we felt it wasn’t necessary. Due to the problems on the previous structure, there was a great deal of scrutiny on the project. We were asked to provide several test panels— one for each day of our shoot to be indicative of the project and material placement. Our test panels proved an added benefit to the structure from the use of the silica fume, which was additional strength. We were already shooting our engineered mixture design that averages over 5000 psi (35 MPa), but these breaks came back as high as 8440 psi (58 MPa). We cured the test panels in the same way we cured the pool, which was through soaker hoses left to flood the structure. Once the pool structure was shot, we flooded it and let it cure for a month. The test panels were pulled out after 7 days and tested at 7, 14, and 28 days. After a month of curing in a flooded state, there were no signs of efflorescing anywhere in the project and no walls showed moisture on the exterior surfaces. We succeeded in providing a watertight, efflorescence-free project with high compressive strengths. Being a glass tile pool, the glass tile manufacturers have specific requirements for the surface preparation. This pool was sprayed with Aquron CPSP and was also coated with Flexcrete after all surface preparations and before the tile application. 26 Shotcrete • Winter 2016


2016WinterShotcreteEMag
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