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2017WinterShotcreteEMag

Rebar team and a few SSG employees to provide equipment support for Merkel and some supervision. With a Memorial Day completion date, SSG did not have the luxury of waiting for good weather to be able to start the shotcrete process. Shotcrete work took place from February 22 through March 4, 2016—a cold time of year in New York. The shotcrete portion of the project was estimated to require approximately 550 yd3 (420 m3) of shotcrete because both the floor and walls were to be shotcreted. The 7700 ft2 (715 m3) floor had many different breaks and shapes in the floor, so it was decided that shotcrete would be the best way to create a monolithic floor. It would have been very difficult to cast over 300 yd3 (230 m3) of concrete with all the contours of the floor in one continuous pour. SSG decided to mobilize their on-site batching equipment for the job. The on-site batching is the first choice for SSG because it allows us to stop and start as needed without worrying about concrete trucks backing up. It also makes it a lot easier to shoot large amounts of material in regular working days without the downtime of concrete trucks switching out or being late. When SSG is shooting pool walls along with pool floors, there is a strict rule of no stepping in the concrete once placed. Once concrete has been placed, it should be allowed to reach final set without any excessive vibration. Additionally, at SSG, cuttings or rebound are never allowed to fall to an area that has exposed reinforcement. To shoot this pool, they began shooting 4 ft (1.2 m) wide strips approximately 3 ft (0.9 m) off of the walls. They then placed more 4 ft (1.2 m) wide strips approximately 10 ft (3 m) apart from one another. These 4 ft (1.2 m) wide strips are easy to finish by hand, along with allowing them to roughen the edge surface to create good joints. The open 10 ft (3 m) wide strips are then filled in later in the process. With the use of a spinning screed, it typically only takes three to four workers to shoot and finish these areas. The simplicity of the spinning screed allows relatively inexperienced laborers to work with the nozzlemen and place a good section of floor while the more experienced finishers are finishing the section of wall that was just shot. After shooting the 4 ft (1.2 m) wide strips, they then shot the coves and up the walls, essentially jumping back and forth between the floors, cove, and walls based on which sections were ready for more material. The pool floor ranged from 10 to 24 in. (250 to 610 mm) thick and the walls were all approximately 14 in. (350 mm) thick. SSG had two wet-mix ACI Certified Nozzlemen and two dry-mix certified nozzlemen on site. The wet-mix process was chosen because of the overall quantity and section thickness of shotcrete required. SSG chooses wet-mix for most commercial pool applications because it allows faster material placement than the dry-mix process. While the dry-mix certified nozzlemen are less familiar with the details of wet-mix placement, they were still helpful to have on the team. With the amount of reinforcing bar in this pool, the ACI Certified Nozzlemens’ knowledge was truly tested. Shooting through two mats of No. 7 (No. 22M) bar certainly requires the skill of a highly trained nozzlemen with classroom education and field experience as well as requiring a highly skilled blow pipe operator. With the quantity and sizes of the reinforcing bar, SSG chose to use non-contact lap splices in the reinforcement on this project. The team used a broom finish on the floor and a cut finish on the walls that would later accept a combination of tile and marcite plaster finishes. Because the business is located in the Northeast, SSG is very familiar with handling cold weather shotcrete projects and was fully equipped for this one. Part of the mobilization Fig. 3: Shotcrete installation—4 ft (1.2 m) wide strips being installed and the 10 ft (3 m) wide openings to be filled in later Fig. 4: Covering with thermal blankets to protect from freezing 34 Shotcrete | Winter 2017 www.shotcrete.org


2017WinterShotcreteEMag
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