Rotary Bored Piling Specialists

Concrete Bleed

Gravity causes the denser aggregate particles to sink in the column of concrete, forcing the free water to rise, if the surrounding ground is unstable to absorb water. The upward movement of the water may concentrate to form a flow path at the edge of the piles or on the reinforcing bars. This concentrated upward flow may erode cementitious material and fine aggregate causing pile integrity problems

Primary Reason
Too much free water in concrete mix and impermeable ground unable to absorb water.
Possible Causes

Concrete mixed with too much water

External ground water pressure is greater than concrete head pressure causing water to enter the concrete column

Pile concrete is placed through standing water at the base of the pile without Tremie technique. Even 400mm of standing water may have a significant effect on the concrete.

Water filled voids in ground cause mixing of concrete with additional water

Larger aggregates settle in concrete mix causing grout and free water to rise

Likely Scenarios
Possible Causes
Concrete mixed with too much water
Likely Scenario
  • Incorrect concrete batching
  • Additional water added
Possible Causes
External ground water pressure is greater than concrete head pressure causing water to enter the concrete column
Likely Scenario
  • Artesian water pressure
  • Delays in concrete placing causes external ground water to have higher head pressure than concrete column
Possible Causes
Pile concrete is placed through standing water at the base of the pile without Tremie technique. Even 400mm of standing water may have a significant effect on the concrete.
Likely Scenario
  • Delay in concreting operation offer completion of pile bore, with water ingress collecting at base of pile
  • How much is too much standing water
Possible Causes
Water filled voids in ground cause mixing of concrete with additional water
Likely Scenario
  • Unknown services e.g. disused pipework containing water
  • Poor pile construction technique of boring “out of casing” in unstable ground
  • Water-bearing unstable granular strata between stable concrete layers
Possible Causes
Larger aggregates settle in concrete mix causing grout and free water to rise
Likely Scenario
  • Poorly graded concrete mix
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