Plastic Concrete

Unlike the conventional concrete with cement, fine aggregate, coarse aggregate and water plastic concrete is deformable, as the name indicates. Its is more impermeable than the ordinary concrete but comparatively the compressive strength is much less than structural concrete because of the addition of bentonite. Bentonite improves the impermeable characteristics of the plastic concrete. Plastic concrete is widely used for the construction of watertight elements of water bearing structures like dams and slurry walls. Slurry walls are normally excavated under bentonite suspension with specialized equipments. The use of bentonite stabilities the trench excavation and it facilitates the extraction of the excavated materials. This method can be adopted to construct very thin and deep, for example 600 millimetre wide and 50 metres deep watertight vertical wall.

Excavation of Trench with Grab	Concreting of the Trench
Measurement of flow	Measurement of temperature
Casting of samples for testing	Tests for Permeability in Triaxial Cell
Tests for Modulus of Elasticity	A sample after compressive strength test

The slurry walls of cut-off walls, the terms usually referred in hydraulic structures are excavated and concreted up to the bottom rock level or the impermeable strata or as per the design depth. Excavations are performed in alternate and then the intermediate panels.

Cement, bentonite, aggregates and water are the ingredients of plastic concrete. The aggregates are normally screened soil or clay with maximum particle size of 20 millimetres. The cement content usually ranges from 80-120 kg/m³ and bentonite content ranges from 20-40 kg/m³ of Concrete. The Modulus of Elasticity of plastic concrete is between 100 and 400 MPa and the Compressive strength at 28 days is about 1-2 MPa.

Typical Modulus of Elasticity Curve