Use of Unbonded Caps in Determination of Compressive Strength of Hardened Concrete Cylinders

콘크리트 원주형 공시체의 압축강도 시험을 위한 Unbonded Cap의 사용

To save efforts for capping in the compressive strength tests of concrete, unbonded capping system has been standardized by ASTM C 1231 and AS 1012.9, respectively. These standards, however, do not sufficiently give a full detail of accessories such as steel retaining cap and rubber pad, especially hardness of rubber. Hence, without testing for sizes of steel retaining cap and rubber pad, tests for the quality control of rubber pads were conducted in detail according to Japanese studies. Based on tests, the range of hardness for rubber pad by the compressive strength(200~ 400kgf/$\textrm{cm}^2$) of concrete has been proposed and the guideline of reuses of a rubber pad is described.