Influence of the sample size and evaluation method on the component‐specific coefficient of variation of concrete compression strength

Abstract It is well‐established that concrete's compressive strength is not a constant, but rather a variable. Smaller variation in these variables can lead to the utilization of more favorable material properties, reducing uncertainties. The research results from about 50 years ago on the variability of these characteristics were subsequently incorporated into both national and international standards. This paper looks at several recent bridge construction projects in southern Germany. Through a statistical analysis of nearly 600 compressive strength test results, it is revealed that the level of variability is lower for a component‐specific variation analysis compared to a structure‐specific or concrete strength class‐specific classification. This approach is initiated by the notion that, for the evaluation of an existing component, only the variation within that component is relevant. When evaluating a specific component in the context of assessing an existing structure, the primary focus should be on the variability within that component, rather than within many other construction projects. Within the individual components, the coefficient of variation is found to be smaller than currently assumed based on the conducted study. Finally, potential explanations for these findings are given.