Evaluation of the potential of corn and sunflower bark particles as bio-aggregates for lightweight concrete

Biomaterials are an alternative to non-renewable materials. Hemp shives allowed developing an industrial sector favorable to sustainable development. Hence, hemp concrete is currently used as filling material in a timber frame (cast onsite, sprayed or precast). Nevertheless, hemp shiv, the reference biobased aggregate, has a limited availability. It is thus necessary to consider other bio-aggregates largely and locally available. Sunflower and corn stalks were selected for their large availability in south-west of France. The objective of this paper is to evaluate the potential of these two agricultural by-products as alternative bio-aggregates for vegetal lightweight concrete throw the determination of aggregate properties and the study of chemical interactions between plant particles water-soluble compounds and a pozzolanic binder. The results revealed a strong deleterious effect of corn water-soluble compounds on the setting and the hardening mechanisms of the pozzolanic binder. A 24 hours long setting delay was not only observed but an almost complete inhibition of the hardening was also highlighted by the mineralogical analysis and the evolution of the mechanical performances. Sunflower particles could be a good candidate for hemp shives substitution, since their characteristics are similar and their impact on the binder setting and hardening is moderate