Low adhesion of the cementitious matrix on the vegetal particles, as well as poor hydration of the cement are the main causes of the poor mechanical performances of vegetal concretes, which limits a large-scale
production of plant-based composites. In fact, vegetal particles have a high capacity to absorb water limiting the hydration of cement. In addition, vegetal particles have the ability to fix ions, like calcium,
avoiding the formation of cement hydrates. To limit these phenomena, it is possible to treat the vegetal particles, by mechanical or thermal actions, in order to modify their surface and reduce their capture
capacity (FNDT, EDTA, NaOH), or to change the cementitious matrix (from Portland cement to plaster or ettringite binder). The assessment of the better compatibility between a binder and a plant with a
simple and reliable experimental test remains an issue.
The research project focuses on the experiment evaluation of the Interaction Transition Zone (ITZ) between the cement and vegetal for different couple cement/ vegetal particles. The protocol consists in studying the surrounding area of the vegetal particles poured in a cement matrix by visual observations (image analysis, microscopy) and microstructural characterization (X-Ray Diffraction, Fourier Transform Infrared Spectroscopy…).
This project will therefore be carried out in these following stages:
- Literature review on cement, plant particles, ITZ (Master thesis, publication),
- Experimental tests with different binders (Prompt cement, pozzolanic cement CEM IV/A (P), LC3 based on a blend of limestone and clay calcined and cement CEM II/C (Q-LL), a sulfo-aluminate cement) and vegetal particles (hemp, rapeseed, miscanthus, bamboo)
- Microstructural (XRD, FTIR, infrared microscopy) and chemical characterisations of ITZ (image analysis, micromechanical characterizations).
- Impact of the couple binder/ vegetal particles on hydration process at the interface.