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2013WinShotcreteEMag

2012 Honorable Mention hydrodemolition and Shotcrete for rehabilitating a Reservoir Spillway By Kyong-Ku Yun, Sung-Yong Choi, and Yong-Gon Kim tplished by hydrodemolition and shotcrete with to break up concrete and is a popular alternativehallengescHydrodemolition uses high-pressure water jetsydrodemolitionh-he rehabilitation of a multi-curved reservoirspillway in Korea was successfully accom careful consideration of the construction material to jackhammering. Water is supplied to the robotic specifications, the importance of curing, and careful machine from a 20,000 psi (137.9 MPa) high- sequencing of the field work. Hydrodemolition was pressure pump with flows of 40 gpm (150 L/m). adopted to selectively remove damaged concrete A hydrodemolition system consists of a high- and the prepared surfaces were cleaned by com- pressure water pump(s), a robotic cutting head, pressed air jets and vacuum cleaners. Then, a high- and a support vehicle or trailer. The trailer carries performance wet-mix shotcrete offered the the: 1) pump; 2) cutting equipment and vehicle; advantages of lower rebound, higher strength, better 3) spare parts and tools; and 4) fuel and water bonding, and improved durability. tanks. The hydrodemolition cutting depth is dependent on the length of time that the water jet the Scope of Work is directed at the concrete surface. The contact The scope of work included a curved spillway exposure time is controlled at the robotic cutter. and a vertical wall. The multi-curved spillway was There are five parameters that determine the qual- 148 ft (45 m) long and 25.6 ft (7.8 m) high and the ity and depth of removal: repaired vertical wall was 32.8 ft (10 m) long and • Rotation speed of the nozzle; 9.8 ft (3 m) high. Figure 1 shows the deteriorated • Angle of the nozzle to the surface; spillway and vertical wall. The project started on • Height of the nozzle above the surface; May 29, 2010, and was completed on June 18, 2010. • Traverse speed; and The project owner was Korea Rural Commu- • Advance distance. nity Corporation, which is a part of the Korean Hydrodemolition was required by project government. The high-performance wet-mix planners who had experienced its significant shotcrete was developed by Professor Yun, work- advantages over traditional impact methods—that ing at Kangwon National University and accord- is, jackhammers and roto-millers—in past work. ing to the requirements of the project owner. The There are many advantages of using hydro- shotcrete contractor was Daesang E&C, who also demolition over traditional removal methods, operated the hydrodemolition works. including: (a) (b) Fig. 1: Deterioration before rehabilitation: (a) spillway; and (b) wall 48 Shotcrete • Winter 2013


2013WinShotcreteEMag
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