Considerations for selecting design properties for RCC dams and dam rehabilitation projects

While roller-compacted concrete (RCC) has become accepted throughout the United States for new gravity dam construction and rehabilitation of both embankment and concrete dams, universally accepted standards for design have been adopted at a slow pace. Several agencies and organizations, such as the Corps of Engineers, the Bureau of Reclamation, Portland Cement Association, and ACI International have actively participated in developing design guidelines. Numerous other agencies, organizations and individuals have also contributed to the industry's knowledge base. However, RCC technology is rapidly changing and, in some instances, available sources of information are conflicting, making the decision process difficult for both the designer and dam safety agency review staff.

Key unhardened RCC design properties include workability, air content, set time, and wet density. Of these properties, workability and set time tend to have the greatest impact on project success and can significantly affect the hardened properties of the RCC. Key hardened RCC design properties include density; compressive, tensile, and shear strength; static and sustained elastic modulus; permeability; durability; and adiabatic temperature rise, coefficient of thermal expansion, specific heat, diffusivity, and conductivity. Certainly many small projects can be successfully designed without determination or understanding of all of these properties. However, there are certain properties that must be known or estimated even for very small projects. In addition to understanding the properties of the parent RCC material, the strength and permeability of lift joints must be understood, particularly for design of a new dam.

This paper summarizes the key RCC material properties required for design of both large and small new dams and rehabilitation projects, and identifies considerations, method and applicable test procedures for determining design properties. Unhardened (fresh) and hardened properties of RCC will be discussed. Each key RCC property required for design and the corresponding accepted test method is discussed. 12 pp.