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2015WinterShotcreteEMag

of approximately 60 yd3 (46 m3). The mixture design included 750 lb (340 kg) of cement with 50 lb (23 kg) of fly ash and 8% batched entrained air, with a water-cementitious material ratio (w/cm) of 0.45. No additional water was added to the delivered concrete out- side of or beyond the total allotted mix water from the plant. Equipment included an Allentown PC 20 shotcrete pump with 4 in. (100 mm) pump dis- charge; an Ingersoll Rand 375 air compressor; 4 x 3 in. (100 x 75 mm) reducing bushing to 3 in. Fig. 7: Curing process for maximum strength gain (75 mm) steel slick line run to pools edge; 3 x 2 in. (75 x 50 mm) reducing bushing at pool edge connected to rubber 2 in. (50 mm) hose connected to 2 in. (50 mm) nozzle body; and miscellaneous shotcrete tools and aids. The placed material was rough-screeded with finishing tools, allowing crews to keep uniform lines and still maintain an excellent bond plain for future plaster finish (Fig. 7). The weather at the time of sprayed applications fell below 32°F (0°C) at night, so heat- retaining blankets were used to protect newly placed material from freeze damage during the hydration and strength-gain process. The shotcrete process made this project both achievable and sustainable. The free-flowing pool design was a key feature for the client and was facilitated through the one-sided, non- restricted forming and installation inherent to the shotcrete process. They were able to install Fig. 8: Finished structure suited to surrounding landscape 6000 psi (40 MPa) watertight concrete to every angle and curve in the pool, with relatively low levels of labor and materials. By contrast, cast-in-place methodology would have required three sides of forming, considering the interior slot overflow/gutter design of the pool. The amount of materials, labor, and energy needed to complete the concrete installation via cast-in- place would have doubled in comparison to the shotcrete process. Final Details The edge detail was created with Roxbury Granite Stone, which is also used on the sur- rounding deck (refer to Fig. 8 and 9). Our masons did a great job of carefully honing the pieces, which range in length from approximately 1 to 4 ft (0.3 to 1.2 m), to create a precise edge with less than 1/8 in. (3.2 mm) tolerance. Each stone was selected, shaped, and marked to indicate its location. It was precision work using material that was a challenge to simply lift into place. Inside the pool, the returns are all wall- mounted. To some, flow returns make the bottom of a pool look like it has a case of the measles. Fig. 9: Tight tolerances and advanced design features facilitated There are five 12 x 12 in. (300 x 300 mm) Pentair by the shotcrete process drain boxes in the floor. Three are for the organic 28 Shotcrete • Winter 2015


2015WinterShotcreteEMag
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