Impact of Bio-Aggregates Properties on the Chemical Interactions with Mineral Binder, Application to Vegetal Concrete

Plant concretes were developed and are currently used as filling material in a timber frame. Their properties are strongly related to the bio-aggregates characteristics. In addition, since hemp shiv, the reference bio-based aggregate, has a limited availability, it is necessary to consider alternative bio-aggregates largely and locally available. Thus, this paper focused on identifying and understanding mechanisms of interaction between different bio-aggregates and mineral binders. To address this issue, the first objective was to determine the properties of five hemp shives and two alternative bioaggregates for vegetal lightweight concrete: corn and sunflower bark particles. The study of the chemical interactions between bio-aggregates and a pozzolanic binder was conducted on model pastes mixed with filtered solutions containing bio-aggregates extractives. The mechanical properties of the paste, as well as their hydration and their mineralogical evolution were studied. In the last part, the mechanical behavior of vegetal concretes was assessed. The results highlight a strong relation between the mechanical behavior of pastes and concretes and the extractive content of the different tested bio-aggregates. Finally, pastes appeared as a relatively good model to predict the behavior of concretes by following their early age performances: setting delay and 3-day mechanical strength