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Low-strength, “plastic” concrete mixtures were proportioned to construct a cut-off wall through permeable features in the foundation of Meeks Cabin Dam, Wyoming. Low strength concrete was required to match the deformation properties of the concrete with the embankment materials in the dam. The mixtures were proportioned with zero (control mixture), 10, 15, and 20 % bentonite by mass of cement plus bentonite. The bentonite reduces compressive strength and elastic properties when compared to conventional concrete. Mixtures were proportioned to meet the desired fresh and hardened concrete properties. All mixtures met the 8 in. (200 mm) slump required for tremie placing. The design compressive strength is 200 lb/in.2 (1,380 kPa) at 7 days and 400 lb/in.2 (2,760 kPa) at 28 days. The 15 % bentonite mixture met the strength requirements and was chosen for more detailed testing. Additional tests evaluated the triaxial shear strength, flow-pump permeability, and erodibility of the low-strength, hardened concrete, and determined the effect of adding a retarding admixture on setting time and slump loss of fresh concrete.
Concrete Cutoff Walls, Controlled Low-Strength Materials, Plastic Concrete, Earth Dams, Rehabilitation
Research Civil Engineer, U. S. Bureau of Reclamation, Denver, CO
Materials Engineering Technician (Retired), U.S. Bureau of Reclamation, Lakewood, CO