Conformity Assessment of Concrete Compressive Strength According to Ukrainian and European Standards

The issues of assessing the compliance of concretecompressive strength according to national and Europeanstandards are considered. It is shown that the concretestrength grade, which was used in the territory of theformer USSR, did not guarantee the correspondingstrength of concrete in products produced at theenterprise, since it did not take into account the actualuniformity of properties and therefore the transitionfrom grades to classes of compressive strength shouldbe considered as a progressive step that allows you toincrease the homogeneity of concrete and the stabilityof its performance.According to EN 206-1, DSTU EN 206:2018and DBN V.2.6-98, the class of concrete in terms ofcompressive strength is determined by the characteristicstrength indicator, which is guaranteed with a 95 %probability, thus, out of 100 tests, the indicators of 95tests exceed the value of the characteristic strengthof concrete. From this further calculations are basedboth in the design of construction projects and in theirtechnological implementation, namely: the requiredstrength of concrete, average strength, determiningwhether the strength of concrete meets the compliancecriteria.The main methods for assessing the compliance ofthe strength of concrete at a joint with a given classaccording to national and European standards arepresented. An analysis of statistical requirements forthe strength properties of concrete was carried out inaccordance with national and European regulatorydocuments. It was found that their implementationensures the production of the required quality.It is shown that the value of the standard deviationcharacterizes the absolute variability of the parameterbeing studied, and the coefficient of variation, equalto the ratio of the standard deviation to the arithmeticmean value of the parameter (for example, strength),characterizes the relative variability. That is, the useof the coefficient of variation makes it possible toevaluate the stability of work (the quality of productionorganization) on different technological lines for theproduction of concrete mixtures, comparing theuniformity of strength of concrete of different classes.According to European requirements, thedetermination of the minimum strength of concreteduring continuous production to obtain the requiredclass is carried out according to two criteria: criterion 1:fcm ≥ fck+1,48σ, and criterion 2: fcm.≥ fck – 4.Calculations were carried out to determine thecompliance of concrete with a given class according toEuropean and Ukrainian standards at different valuesof the standard deviation, and, accordingly, differentcoefficients of variation. The results obtained are similarand have minor differences, which means that thetransition to European standards for assessing thequality of concrete should not cause any problems.Thus, taking into account the gradual transition ofthe regulatory framework of Ukraine to the Europeanone, it is advisable to revise DSTU B V.2.7-224 with theintroduction of the requirements of EN 206-1.