Assessing variability of hemp concrete properties during experimental tests: a focus to specimens' number

Abstract

Several parameters influence the mechanical properties of hemp concrete. Some are due to the nature of its constituents such as the aggregate size, the type of binders, and other parameters are due to manufacturing method, such as the compaction energy and the molding method as well as the methods used for its properties characterizations. This paper is interested in the study of the variability of hemp concrete properties taking into account the number of specimens used during experimental investigations. The hemp concrete properties considered are: the maximum compressive stress and apparent modulus.  A methodology with the goal to evidence how the increase in number of specimens may improve the accuracy for obtained results has been used. The mean, minimum and maximum values, with also standard deviation and the confidence interval have been analysed. Beyond, a comparative analysis between the theoretical distribution and the observed experimental distribution in each set by Q-Q plots allowed a better appreciation of the accuracy in obtained results. With this study, it has been highlighted that at least a set of six specimens is necessary and recommended for accurate results during experimental investigations.