Determination of concrete quality in a structure by combination of destructive and non-destructive methods

The paper describes a mathematical model for determination of parameters for concrete compressive strength based on indirect measuring of values (ultrasonic pulse velocity, rebound hammer index, etc.) which are easier to measure and which are, in a way (linear regression), related to the concrete compressive strength. A relationship has been determined between random sample values for direct and indirect measuring yields equally good statistical estimations of mathematical expectations and dispersion.