Core extraction and testing of concrete covers obtaining, preparing, and testing cores drilled from concrete for compressive strength test of casted concrete structures.
Reference Standard codes:
- ASTM code C 42
- IS 516
- IS 1199
General Tips of Core Extraction:
- Concrete strength is affected by location of the concrete in structural element, with concrete at the bottom tending to be stronger than the concrete at the top.
- Core strength is also affected by core orientation relative to the horizontal plane of the concrete as placed, with strength tending to be lower when measured parallel to the horizontal plane.
- The strength of concrete measured by test of cores and beams is affected by the amount and distribution of moisture in the specimen at the time of test.
- These factors shall be considered in planning the locations for obtaining concrete samples and in comparing strength test results.
Apparatus for Core Extraction of concrete:
- Core drill, for obtaining cylindrical core specimens with diamond impregnated bits attached to the core barrel.
- Saw for trimming the ends of the core. The saw shall have a diamond or silicon carbide cutting edge and shall be capable of cutting specimens that confirm to the prescribed dimensions without excessive heating or shock.
Samples for core testing:
- Samples of hardened concrete for use in the preparation of strength test specimens shall not be taken until the concrete is strong enough to permit sample removal without disturbing the bond between the mortar and the coarse aggregates.
- Also samples that have been damaged during removal shall not be used unless the damaged portions are removed and the resulting test specimen is having the required length.
- Samples containing embedded reinforcement cannot be used for the test
Core drilling :
- Core specimen shall be drilled perpendicular to the surface and not the formed joints or edges.
- Record and report the approximate angle between the longitudinal axis of the core drilled and horizontal plane of the concrete as placed.
- A specimen drilled perpendicular to a vertical surface, or perpendicular to a surface with a batter, shall be taken from near the middle of a unit of deposit when possible.
Slab removal: remove a slab sufficiently large to secure the desired test specimen to without inclusion of any concrete that has been cracked, spalled, undercut or otherwise damaged.