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2015WinterShotcreteEMag

clean water and allowed to reach saturated surface- dry condition. A minimum of 1-1/2 in. (38 mm) of King Packaged Materials MS-W1 with poly fibers was applied to the wall surfaces and finished with steel trowel to provide a tight, level surface. All newly placed concrete was water cured for 7 days. Site Conditions The site provided many challenges during the life of the project. The existing tanks were con- structed with the finished floor elevation 8 ft (2.4 m) below grade. The water table in this loca- tion was higher than the existing floor elevation, causing groundwater to seep into the tank through floor sumps and at the floor-to-wall construction joint. A dewatering plan was implemented that included installing dewatering wells around the tank perimeter to draw down groundwater eleva- tion. This dewatering system was operated and monitored 24/7 to provide dry working conditions during shotcrete and protective lining operations. The only access available to each of the tanks was from the roof, through existing 42 x 42 in. (1.1 x 1.1 m) roof hatches. No additional openings were allowed, thus limiting the size of access equipment that could be used to complete the work. Electric scissor lifts were selected to access the walls. Due to the small roof openings, the lifts were disassembled and lowered into the structure in pieces and reassembled inside the tank. The smaller tanks and areas with limited work area required scaffolding to reach all repair areas. Fig. 2: Poorly consolidated concrete Fig. 3: Honeycomb at cold joint Shotcrete • Winter 2015 41


2015WinterShotcreteEMag
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