Nowadays concrete core test is a famous and well-established method for the assessment of the compressive strength of the hardened concrete.
Comparison of Core and Cube Compressive Strength of Hardened Concrete by IJBSTR Publication - Issuu
Non-destructive Concrete Tests (NDT) for Structure Strength
Test on Hardened Concrete - Strength, Compression & Durability - Concrete Network
How to Get the Best Results from Concrete Core Testing
Concrete core testing Concrete coring.(Property inspection)
Compressive Strength - an overview
Test on Hardened Concrete - Strength, Compression & Durability - Concrete Network
Non-destructive Concrete Tests (NDT) for Structure Strength
Hardened Concrete Core Test for Compressive Strength