The core test provides the visual inspection of the interior of the concrete and direct measurement of the compressive strength. Other physical properties, such as, density, water absorption, indirect tensile strength and expansion due to alkali-aggregate reaction can also be measured. After strength testing, these can be used as samples for chemical analysis. The procedure has been standardized by BS, ASTM and ACI codes. IS-1199-1959 For Field Core Cutting and IS-516-5.5- 1959 for Lab compressive strength.
In core testing, the determination of core size and location is a crucial factor. The test should be taken at points where minimum strength and maximum stress are likely to coincide. But, at the same time, the core cutting causes some damage to the member and may impair the future performance of the member. Therefore, in slender members, the core should be taken away from the critical section. For compression testing, the diameter of the core should be at least three times the nominal maximum aggregate size. The accuracy of the test increases with the ratio of core diameter to the aggregate size. The generally recommended length to diameter ratio of the cores is between 1 to 2.
The core samples can be used for determination of unit weight, estimation of voids, and chemical analysis, a graphic analysis and analysis. Broken samples from the cores can be used to determine the pH value and the chloride content in the sample. These tests on cores and core samples will also provide information that can be used to assess the state of corrosion of reinforcing steel.