A surrounding encasement of an element such as a pier column or pile, made of concrete or fabric, is called what?

• A. Sheath
• B. Casing
• C. Jacket
• D. Coating

Answer: (C)

A jacket is an external protective shell that surrounds a structural member like a pier column or pile. It serves to confinement, protection, and strength: wrapping the existing element with concrete or fabric (such as FRP) increases its cross‑section, stiffness, and durability, and can restore or enhance load capacity after deterioration or damage. Concrete jackets are common for retrofits, while fabric jackets provide a lighter, often easier-to-apply form of reinforcement.

Coating is only a surface layer and doesn’t form a full enclosing shell around the member, so it doesn’t provide the same level of reinforcement. A casing is typically a tubular enclosure used for things like pipes or boreholes, not the standard retrofit term for reinforcing a pile or column. A sheath is a general protective cover but is less specific to the structural retrofit context. Hence, the term that fits a surrounding encasement made of concrete or fabric is jacket.