Roller compacted concrete and stepped spillways

The use of roller compacted concrete (RCC) for new dam construction and for rehabilitation of existing darns has gained wide acceptance throughout the world. RCC is a zero slump concrete that is transported, spread and compacted using traditional earth moving equipment. The placement of horizontal to near-horizontal lifts typical of RCC construction lends itself to the forming of steps into the downstream edge of each lift. Recognition of the benefits of steps, coupled with ease of construction, has led to numerous downstream facing alternatives. A variety of alternative step treatments and approaches to forming have been developed to address a wide range of issues such as durability, aesthetics, constructability and cost. Facing alternatives include formed and unformed steps of exposed RCC, grout-enriched RCC, cast-in-place concrete, and precast concrete. Each of these alternative treatments brings with it its own unique benefits, limitations and design detailing. The development of RCC technology and the evolution of RCC materials science have indirectly led to a rebirth in the use of stepped spillways.