Investigating the unseen flow of concrete in deep foundation construction-Paper

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The study uses computational fluid dynamics (CFD) to investigate how tremie-concrete consistency and reinforcement cover-zone size affect concrete flow and defect risk in bored piles. OpenFOAM simulations model concrete as a non-Newtonian Bingham fluid, alongside support fluid and air, in a representative reinforced pile geometry. Twenty configurations combine slump-flow values of 350–590 mm with cover zones of 25–250 mm.<br /><br />Simulations show that concrete exits the tremie, turns upward within the reinforcement cage, and then flows laterally into the cover zone. Flow can slow sharply there, leaving concrete largely undisturbed once placed. The results reproduce mattressing—layered, uneven filling observed in exposed piles—and indicate that its angle changes with the dominant flow direction as the pile fills.<br /><br />Both lower-consistency concrete and smaller cover zones restrict flow, increasing mattressing, the slope of concrete within the cover zone, and the level difference between concrete inside and outside the reinforcement cage. These features can trap debris or support fluid, create voids, and leave reinforcement inadequately covered. Cover-zone size has a strong influence on mattressing: larger zones reduce its severity, while very small zones can produce mattressing even with high-consistency concrete. Concrete consistency more strongly affects the concrete-level difference. The greatest risk occurs when low-consistency concrete is combined with a small cover zone.<br /><br />The authors recommend avoiding small cover zones where possible and using high-consistency concrete when design constraints make them necessary. The findings indicate general trends rather than definitive acceptance limits: the model treats concrete as homogeneous and does not capture aggregate-related blockage, and the predicted defect patterns have not been fully validated through equivalent physical parametric tests.

Keywords

computational fluid dynamics

CFD

OpenFOAM

tremie concrete

bored piles

Bingham fluid

reinforcement cover zone

slump flow

mattressing

concrete defects