Bentonite for Diaphragm Walls: Selecting Slurry for Mixing and Recycling

Diaphragm-wall construction connects excavation, slurry support, solids separation and concrete placement.

Bentonite selection should therefore consider the entire slurry circuit.A fresh mixture that performs well in a small laboratory container may require further evaluation before use in a recycling plant.

Understand the Slurry’s Functions
In cutter-based diaphragm-wall construction, bentonite suspension can support the excavation and transport excavated solids to a desanding plant. BAUER describes this relationship between the cutter, slurry circuit and separation equipment.

The slurry must meet the project’s support requirements while remaining manageable within the pumping and treatment system.

Evaluate More Than Initial Viscosity
Useful evaluation includes hydration behavior, density, viscosity, filtration characteristics and response to representative excavated material.

The objective is a balanced fluid. A higher viscosity reading alone does not establish better support or more efficient recycling.

Tests should reproduce the proposed water supply, mixing energy and preparation time.

Follow Changes During Recycling
Used slurry contains a changing mixture of bentonite and excavated particles.

Desanding removes selected solids, but fine particles can remain in circulation. Comparing fresh and recycled slurry helps identify changes that may require further treatment, adjustment or replacement.

Sample consistently at defined points in the circuit. Interpret the results together with separation-plant performance and the project’s acceptance criteria.

Adapt to the Project Environment
Where the water supply varies, establish procedures for checking new sources. Where mixing temperatures change seasonally, confirm hydration under the expected operating conditions.

These questions are relevant to projects in Africa, the Middle East, Russia and South America without assuming identical conditions across those markets.

Build a Practical Supply Specification
Buyers should request representative samples, batch identification and test results with methods. Acceptance should connect the supplied powder to slurry prepared under agreed conditions.

HERMANO supplies bentonite for construction-slurry evaluation. Share your excavation method, recycling equipment and required slurry properties to discuss candidate materials.