RRT3: statistical analysis of hemp concrete mechanical properties variability

Abstract

The study has been carried out in the context of a working group within the RILEM Technical Commitee 236-BBM 'Bio-aggregate-based building Materials'. It focusses on statistical analysis of hemp concrete properties. The objective is to determine statistically the variability for material density, compressive strength and Young’s modulus. The considered parameters are: the testing laboratory equipment, the hemp shiv type, the batch and the specimen size. Two types of hemp shiv have been used with two batches for each one. Two specimen sizes were used: 11x22 cm and 16x32 cm. Specimens were manufactured in one laboratory in order to ensure the homogeneity of studied material. After 90 days of drying under the same conditions, they were transported to ten different laboratories for compressive testing. A drying protocol during 48 hours was applied by all laboratories. Then, a unique protocol for compressive testing has been applied by each laboratory. Finally, data have been collected together for statistical analysis. The obtained results show an accurate repeatability for the compressive strength and the dry density; however, the Young's modulus results show a large variability.