Setting and Drying of Bio-Based Building Materials

Abstract

Bio-based materials become successful in the field of building construction because of their sustainability and environmental benefit. In the present chapter, we focus on one of them: Hemp Concrete. This material is made out of hemp shivs mixed with a pre-formulated lime based binder and water, and can be manufactured through three classical processes: spraying, moulding or mechanical mixing and tamping. Similarly to classical concrete, setting and drying are important stages since it influences the mechanical and hygrothermal properties. Here, setting and drying stages are investigated through different experiments performed on several instrumented blocks and on a large-scale wall during the curing time. The instrumentation (thermocouples, humidity sensors, weight-scales) allows investigating the drying kinetics and apprehending the hygrothermal behaviour of the material. It is observed that manufacturing process influences the initial water content whereas the hygrothermal behaviour depends on the material formulation. In addition, a model of multi-physics knowledge taking into account the various couplings is developed to predict desorption kinetics. Particular attention is paid in the experimental determination of hygrothermal properties. A roughly good agreement was found between simulations and experiments for different conditions.