CONFORMITY ASSESSMENT OF CONCRETE COMPRESSIVE STRENGTH ACCORDING TO UKRAINIAN AND EUROPEAN STANDARDS

Abstract

The issues of assessing the compliance of concrete
compressive strength according to national and European
standards are considered. It is shown that the concrete
strength grade, which was used in the territory of the
former USSR, did not guarantee the corresponding
strength of concrete in products produced at the
enterprise, since it did not take into account the actual
uniformity of properties and therefore the transition
from grades to classes of compressive strength should
be considered as a progressive step that allows you to
increase the homogeneity of concrete and the stability
of its performance.
According to EN 206-1, DSTU EN 206:2018
and DBN V.2.6-98, the class of concrete in terms of
compressive strength is determined by the characteristic
strength indicator, which is guaranteed with a 95 %
probability, thus, out of 100 tests, the indicators of 95
tests exceed the value of the characteristic strength
of concrete. From this further calculations are based
both in the design of construction projects and in their
technological implementation, namely: the required
strength of concrete, average strength, determining
whether the strength of concrete meets the compliance
criteria.
The main methods for assessing the compliance of
the strength of concrete at a joint with a given class
according to national and European standards are
presented. An analysis of statistical requirements for
the strength properties of concrete was carried out in
accordance with national and European regulatory
documents. It was found that their implementation
ensures the production of the required quality.
It is shown that the value of the standard deviation
characterizes the absolute variability of the parameter
being studied, and the coefficient of variation, equal
to the ratio of the standard deviation to the arithmetic
mean value of the parameter (for example, strength),
characterizes the relative variability. That is, the use
of the coefficient of variation makes it possible to
evaluate the stability of work (the quality of production
organization) on different technological lines for the
production of concrete mixtures, comparing the
uniformity of strength of concrete of different classes.
According to European requirements, the
determination of the minimum strength of concrete
during continuous production to obtain the required
class 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 the
compliance of concrete with a given class according to
European and Ukrainian standards at different values
of the standard deviation, and, accordingly, different
coefficients of variation. The results obtained are similar
and have minor differences, which means that the
transition to European standards for assessing the
quality of concrete should not cause any problems.
Thus, taking into account the gradual transition of
the regulatory framework of Ukraine to the European
one, it is advisable to revise DSTU B V.2.7-224 with the
introduction of the requirements of EN 206-1.