Stochastic identity of test result series of the compressive strength of concrete in industrial production conditions

The article provides the scientific basis of interval identity of the compressive strength of concrete, as well as includes calculation examples concerning the application of concrete apron paving with the use of concrete pavers. It was found that in order to control the compressive strength of concrete formed in a continuous, cyclically repetitive mode, standard statistical assessment of concrete strength is not sufficient since, in the case of deviations in the studied characteristics of concrete from the project assumptions, it is not possible either to implement corrections in the concrete manufacturing process or to change the location of the concrete structure with decreased strength parameters. Due to this, the analysis of the qualitative and quantitative production of concrete mix and its application at the construction site required the use of appropriate calculation procedures, allowing to extract subsets of the results of the compressive strength of concrete projecting technological disturbances and assign to them time intervals, in which the disturbances occurred. This is a completely different approach to the issue of determining the compressive strength properties of tested concrete volume than presented in the construction standards. For this reason, to present the real picture of the compressive strength variability, the division of tests results was made by grouping the data belonging to one population with probabilistically stabilized strength parameters forming a family of concrete. In order to do this it was necessary to use appropriate calculation procedures based on verification of statistical hypotheses. The authors proposed three independent methods based on statistical tests: Pearson χ2 test, t-Student's test and Mann–Whitney's U test. The results series were divided into families of concretes and were given different sensitivity of each method. However, the breakdown of the whole series achieved by the three methods is comparable and occurred in the areas of high variability of strength.