What is Core Test?
Core test is a well established method, generally performed in the area of concrete industry to assess whether the suspect hardened concrete complies with strength-based acceptance criteria or not; and sometimes it becomes the unique tool for safety assessment of existing concrete structures.
In this test, concrete cores from the hardened concrete are extracted using the core cutting machine and after the preparation of specimens, their compressive strength are determined.
Why is it necessary to conduct a core test?
The core test is critically required when the results of Concrete cubes are not giving satisfactory results or shows some uncertain results.
In case of doubt regarding the grade of concrete used, either due to poor workmanship or based on results of cube strength test, compressive strength tests of concrete core may generally be carried out.
In addition, it is used to determine concrete strengths in an existing structure for the evaluation of structural capacity or safety assessment of existing structure or to assess its capacity in case some additional lading is proposed to be put.
For the rehabilitation of the existing structure, testing of the concrete element is of great importance and core testing is one of the primary methods to evaluate the strength of the existing structure.
What is Capping and its role in the results?
The extracted cores from the structure do not have smooth/even surfaces. In order to have a uniformly distributed load on the entire core specimen, the ends of the specimen should have a smooth, parallel, uniform bearing surface and shouldn’t depart from a plane by more than 0.05 mm. To get the same, both ends of the core may either be cut/ground to have plane surface not departed by more than 0.05 mm and tested without end caps; or the ends of the specimen are treated/coated with a thin layer called ‘capping’ before testing.In this test, concrete cores from the hardened concrete are extracted using the core cutting machine and after the preparation of specimens, their compressive strength are determined.
