Support fluid can remain stable enough for excavation while becoming too contaminated for final construction. The practical decision is whether the fluid can be recovered or should be replaced.

Identify the contaminant

High density + high sand indicates coarse solids. High density + low sand points toward fine silt, clay or rock fines. Cement contamination is a separate chemical event that can also change pH and rheology.

Desanding

Use mechanical separation for coarse solids and verify improvement from before/after density and sand measurements. If sand falls but density remains high, fines still dominate.

Replacement is a normal control action

Partial or full replacement becomes logical when fine solids cannot be removed economically, viscosity remains uncontrollable, cement contamination is significant or pre-concrete criteria repeatedly fail.

Do not confuse slurry and bottom cleanliness

Clean slurry does not prove a clean pile base, and a cleaned base does not prove the slurry is acceptable. Both require separate verification.

Frequently asked questions

Does replacing slurry mean the product failed?

No. Replacement can be the correct solids-management decision.

Can dilution clean contaminated slurry?

Dilution can lower the measured density but does not physically remove the existing solids.

Should polymer be added to dirty polymer slurry?

Only if a genuine formulation deficit is demonstrated; it does not remove existing contamination.