Is hemp lime concrete a mix of hemp and lime?

Abstract

Hemp lime concrete is a mix of hemp shiv glued in a mineral binder. Such concrete is characterized by low thermal conductivity and interesting hygric properties. The aims of this study realized in the frame of ISOBIO Project is to understand which is the contribution of each component of the hemp lime concrete to the thermo-hygric properties of the mix. The study focuses on the case of a commercial hemp shiv (Biofibat®, CAVAC France) and a lime based binder (ThermO®, BCB). The measurement of thermal conductivity and Moisture Buffer Value are performed on some conventional hemp lime concrete formulations. On the other hand, the same measurements are performed on hemp shiv alone (at different density) for several grading showing that thermal Conductivity and MBV evolves according to the density. The last measurements are realized on samples realized with ThermO® lime matrix foamed to achieve sufficiently low densities ranging from 500 kg/m3 to 1100 kg/m3. The comparison of results obtained on each component and on mixes for the same range of density is full of interest to evaluate occurrence of a synergetic effect, or not. The data are used to adjust a model useful for the optimization of the mix proportioning.