Estimation of the characteristic compressive strength value of concrete based on the current code recommendations

The use of cores is an integral part of the assessment of existing structures that are modernized, redesigned or have been damaged. Evaluation of the test results and the estimation of characteristic values of compressive strength can be performed according to the statistical method proposed by the Annex D of the PN-EN 1990 [1] standard, and  also according to the PN-EN 13791 [2]. The procedures recommended in these both documents are different which can lead to various assessments of the characteristic values. The author has been verified whether the empirical relationships, defined in PN-EN 13791 [2], lead to obtaining larger values of characteristic strength and, consequently, to  estimation at the unsafe region. The characteristic compressive strength was of determined in accordance with the recommendations of  the PN-EN 13791 code [2] and the PN-EN 1990 - Annex D [1].