# What Is a Cone in Construction?
**In construction, a cone refers to a cone-shaped recess or element. Most commonly, it describes the tapered plastic or metal spacer used in concrete formwork systems that leaves a conical hole in the finished concrete surface when the formwork is removed. It can also refer to the tapered tip of a driven pile.**
## Cones in Concrete Formwork
When building concrete walls, two parallel formwork panels are held together by tie rods that pass through the wet concrete. At each end of the tie rod, a cone-shaped spacer sits against the formwork panel. This cone serves two purposes:
– **Spacing** — it maintains the correct distance between formwork panels
– **Sealing** — it prevents concrete from leaking out around the tie rod
After the concrete cures and formwork is stripped, the cones are removed, leaving characteristic conical recesses in the concrete surface. These holes are then filled with mortar or left exposed as a design feature in architectural concrete (fair-faced concrete).
## Cone Tips on Piles
In foundation engineering, a cone also describes the pointed or tapered tip of a driven pile. The cone shape helps the pile penetrate the ground more easily during driving. Steel or concrete piles often have a prefabricated cone tip welded or cast onto the bottom.
## Cone Penetration Test (CPT)
A related use of the term is in geotechnical investigation. The cone penetration test pushes a standardized cone-tipped probe into the ground to measure soil resistance, helping engineers determine soil bearing capacity before designing foundations.
## Filling Cone Holes
For watertight or finished concrete, cone holes must be properly sealed. This is done with tapered plugs, specialized mortar, or expanding fillers that match the cone shape exactly.
## Related Terms
– Formwork
– Tie rod
– Fair-faced concrete
– Pile driving
– Cone penetration test
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