(1) This document: - gives methods and procedures for the estimation of the in situ compressive strength and characteristic in situ compressive strength of concrete in structures and precast concrete components using direct methods (core testing) and indirect methods, e.g. ultra-sonic pulse velocity, rebound number; NOTE To align with the design standard EN 1992-1-1, where the compressive strength is based on 2:1 cylinders, the in situ compressive strength is based in 2:1 cores of diameter ≥ 75 mm. - provides principles and guidance for establishing the relationships between test results from indirect test methods and the in situ compressive strength; - provides procedures and guidance for assessing the conformity with the compressive strength class of concrete supplied to structures under construction where standard tests indicate doubt or where the quality of execution is in doubt. (2) This document provides requirements for determining the in situ strength at test locations and the characteristic strength of test regions, but how this information is to be applied needs to be considered in the light of the specific situation and engineering judgement applied to the specific case. (3) This document does not include the assessment of the quality of concrete for properties other than compressive strength, e.g. durability-related properties. (4) This document is not for the assessment of conformity of concrete compressive strength in accordance with EN 206 or EN 13369, except as indicated in EN 206:2013+A1:2016, 5.5.1.2 or 8.4. (5) This document does not cover the procedures or criteria for the routine conformity control of precast concrete components using either direct or indirect measurements of the in situ strength. (3) This document does not include the assessment of the quality of concrete for properties other than compressive strength, e.g. durability-related properties. (4) This document is not for the assessment of conformity of concrete compressive strength in accordance with EN 206 or EN 13369, except as indicated in EN 206:2013+A1:2016, 5.5.1.2 or 8.4. (5) This document does not cover the procedures or criteria for the routine conformity control of precast concrete components using either direct or indirect measurements of the in-situ strength.