SCOPE AND FIELD OF APPLICATION
This NORDTEST method is intended for the determination of the force that is needed to break off a concrete cylinder from a completed object of the measures stated in Fig. 1. This force is here defined as the breaking force.
The cylinder may be taken out either after the concrete is cured or, by sampling from a horizontal surface, be formed with the aid of a sleeve inserted in the fresh concrete after the preparation of the surface has been completed.
The method may be used for the evaluation of the compressive strength in completed object with the condition that the values obtained according to the method have been calibrated for concrete with a known compressive strength and of the same composition as the concrete whose compressive strength one intends to evaluate.
The relationship between the force and the tensile strength of the concrete may then usually be expressed in a linear function.
The method may also be used for the determination of a bond or an adhesion in joints. Then the height of the test specimen, and if a break has occured in the joints should always be stated in the test report.
The core bending test may also be used to determine if the strength of the object has achieved a sufficient level in relation to, e.g. - prestressed concrete (for pre-tensioned and post-tensioned concrete)
- form stripping
- protection against freezing that may cause damages
- termination of curing
The method can not be used when the temperature of the concrete is lower than 0 ºC.
The number of test points and the age of the concrete at the time of testing are not considered in the method.