ACI 207.5R-11 Report on Roller-Compacted Mass Concrete

ACI 207.5R-11 Report on Roller-Compacted Mass Concrete. 1.3.3 Lift configurations—Most RCC dams have horizontal level RCC lift surfaces. Several dams have a cross-fall slope in the upstream direction to increase the resistance to sliding. Miel II Dam used a 1 on 100 cross-fall slope (Marulanda et al. 1992), and Saluda Dam in Columbia, SC, completed in 2004, used a 1 on 30 cross-fall slope. Due to high rainfall at Ralco Dam, Chile, RCC lifts were placed at 1% downstream cross fall to improve drainage (Croquevielle et al. 2003). For the taller RCC dams being built in particularly high seismic regions, lift joint strength and impermeability are crucial design parameters. To maximize lift joint strength properties, successive RCC lifts should be placed before the initial set of the previous lift has occurred. If no retarder is used in the RCC mixture, most mixtures will have an initial set time of 1 to 3 hours; for large dams, it may take between 15 and 30 hours to cover one lift. The Ta Sang Dam in Myanmar will have 32.3 million yd 2 (2700 hectars) of total lift joint surface area, an average of over 70,000 yd 2 (5.8 hectars) per lift. With the normal horizontal lift construction method, it would take many hours to place one lift. The sloping layer placement method was developed in China as a method to improve lift quality, maximize strength properties, and minimize the use of bedding mortars. 1.3.4 Design sections—The vast majority of RCC gravity dams have vertical upstream faces and sloping downstream faces. The downstream slopes have ranged from 1H:1V to 0.8H:1V, with a few exceptions. Upper Stillwater Dam has a compound downstream slope. The lower two-thirds of the face was at a 0.6H:1V, and the upper section was at 0.32H:1V. At Olivenhain Dam, the slope was placed at a 0.8H:1V, but transitioned on a 232 ft (70 m) radius to near vertical on the upper quarter of the slope. The radius concept was used to reduce any stress concentrations at an abrupt change in section slope. Spain has more than 24 RCC dams, and all are straight gravity dams with the exception of one arch-gravity dam. Several of these dams have a sloping or battered upstream face to provide the necessary stability. Santa Eugenia Dam has a 0.05H to 1V upstream face, and Val Dam has a 0.2H to 1V upstream slope transitioning to...