Determination of High Performance Concrete Strength by Means of Impact Hammer

Currently, in civil engineering, high performance concrete i.e. concretes whose minimum compression strength is equal or more than 65 MPa are increasingly used. Side effect of it is need for determination of their construction strength. In particular, recently built high performance structures suffer from sampling of drill cores. Therefore, noninvasive impact hammers – to be specific Schmitt impact hammer – were used for determination of structural concrete strength. However, efficiency of calibration correlation using impact hammer volume indicated in standards (e.g. EN 137914, CSN 731373) or by impact hammer manufacturers is disputable since these correlations were developed at the time such concretes were uncommon. This paper indicated calibration correlations as elaborated for high performance concretes class C 55/67 to C 80/95; 2 to 60 days old, for Schmidt impact hammer type N & L. Calibration correlations generated feature high degree of correlation and practical utility. Moreover, these calibration correlations here are compared with correlations given for concrete strength calculation as stated by technical standards, and impact hammer manufacturer; this implies that these correlations indicated in EN 13791, CSN 731373 and declared by impact hammer manufacturer are inapplicable for determination of high performance concrete strength by means of impact hammer.