Plastic Concrete for Cut-Off Walls: a review on material behaviourÂ-Paper

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The paper reviews the material behaviour of plastic concrete used in cut-off walls to control seepage through earthen dams. Unlike conventional concrete, plastic concrete combines low cement content and a high water–cement ratio with bentonite or other water-binding additions. These additions stabilize the mix, while fine-to-medium aggregates and retarding admixtures support placement by tremie.<br /><br />Plastic concrete is a low-strength, low-stiffness material with greater deformation capacity than ordinary concrete. Its 28-day compressive strength is typically about 0.5–2.5 MPa, and strength generally decreases as the water–cement ratio rises. Strength continues developing beyond 28 days, so testing at later ages may be appropriate. Reported elastic moduli vary substantially with testing method, with concrete and geotechnical standards producing different values. The material also exhibits pronounced creep and stress relaxation, which may help limit stress peaks and cracking.<br /><br />Hydraulic conductivity generally increases with higher water–cement ratios and lower strength, but may decrease over time as hydration and consolidation progress. Typical reported permeability is approximately 10⁻⁹–10⁻⁸ m/s. Because testing methods and procedures strongly affect measured properties, careful specification of loading rates, deformation measurement and test ages is essential.<br /><br />The review concludes that current designs often oversimplify plastic concrete as linear elastic, despite its ductile, time-dependent behaviour. Further research is needed on its mechanical and hydraulic properties, especially creep, relaxation, constituent interactions and testing methods, to support more realistic cut-off-wall design.

Keywords

plastic concrete

cut-off walls

seepage control

earthen dams

water-cement ratio

bentonite

compressive strength

elastic modulus

creep

hydraulic conductivity