Bored Pile Slurry Testing: Density, Marsh Viscosity, pH and Sand Content
Bored-pile slurry QC should interpret density, Marsh funnel, pH and sand content together. A single number rarely identifies the cause of a field problem.
Density
Density is one of the best contamination indicators. High density + high sand points toward coarse solids; high density + low sand points toward silt/clay fines.
Marsh funnel
Marsh time is a quick field flow index, not complete rheology. High Marsh can result from product concentration or solids contamination. Low Marsh can result from dilution, poor hydration or polymer/soil interaction.
pH
pH is a chemical warning signal. Use it to track make-up-water conditioning, formation chemistry and possible cement contamination. Do not dose SODA ASH solely to chase a pH number.
Sand content
The test describes the coarse fraction retained by the specified screen. Low sand does not rule out fine-solids contamination.
Sample stage and depth matter
Fresh, working and pre-concrete samples answer different questions. Surface and bottom samples can differ substantially. Always record time, sample location, depth and formation.
Diagnostic matrix
| Pattern | First direction |
|---|---|
| High Marsh + normal density | Concentration/rheology |
| High Marsh + high density | Solids contamination |
| Low Marsh + normal density | Dilution/under-treatment/preparation |
| High density + low sand | Fine solids |
| Sudden high pH after concrete | Cement contamination |
Use the high-density troubleshooting guide for deeper diagnosis.
Frequently asked questions
Is one universal QC table valid for bentonite and polymer?
No. Use product/project-specific limits.
Does passing Marsh mean the slurry is clean?
No. Density and solids can still be unacceptable.
Should the surface sample be used for final concrete acceptance?
Use the representative sampling locations required by the project procedure.