Sufficient number of core samples and method to determine compressive strength of in-use and reclaimed concrete elements

Abstract

Reusing reclaimed concrete elements is not a widespread practice, although it could help to decrease the carbon footprint of new construction significantly. As reuse needs to be safe, the properties and reusability of the element intended for reuse need to be ensured reliably. When the current statistical method to evaluate characteristic compressive strength with a small number of samples is used, overestimation of the strength has occurred. Moreover, the issue has been considered by only a few studies. Therefore, this study considers the sufficient number of samples and the suitability of the statistical method for the evaluation of the characteristic compressive strength with core samples. With statistical analysis and representative cases, it finds that 12–15 samples should be sufficient for a reliable assessment of a population. However, the compressive strength must be determined on a case-to-case basis for each building and element type. The results also highlight that the statistical method for characteristic compressive strength can give significant overestimations from 1 up to 10 MPa. Some modifications are thus needed to the method. The paper presents correction factors for the statistical method to determine characteristic compressive strength.