Test cylinder
A molded sample of fresh concrete cast on site, cured under controlled conditions, and later crushed to verify that the delivered mix met its specified strength.
What does test cylinder mean?
Cylinders are cast in sets so that specimens can be broken at different ages, typically an early age for information and a later age for acceptance. How they are handled during their first day on site determines whether the results mean anything, since a cylinder that froze, baked, or got jostled will break low regardless of the mix. Standard-cured and field-cured specimens answer different questions and are not interchangeable.
In practice
The row of plastic molds sitting in a cooler or a curing box beside a commercial pour is the paperwork trail for the whole placement.