Directors : N. Roussel, M. Bornert

During automated 3D printing of concrete structures, since the fresh material is deposited and shaped without formworks, the protection of these formworks against the environment before they are stripped or removed does not exist anymore. Outdoor, the material will be therefore exposed critically to heat, humidity and wind, able to damage the final printed element. How transfer indoor technologies to outdoor real construction site ?

X-ray Computed Tomography study at the filaments interface in additive manufacturing

This project aims at investigating the physical origin of the mechanical weakness at the interface between extruded layers in a dry environment. The deformation and micro-cracking of cement-based materials with various stiffness and permeability are assessed using X-ray Computed Tomography. 2D and 3D digital image correlation methods are used as an aid to characterize the microstructure evolution of the materials and improve either the process and/or the material.

Interaction between binder and powders for powder-bed 3D printing

The high resolution and geometrical conformity of a printed element depends both on grains size and binder penetration in the case of powder-bed 3D printing techniques. This project aims at studying the capillary driven penetration of a liquid binder in a powder bed such as water in cement, water in clay or sodium silicate in metakaolin. The penetration depth of the binder over time for various binder viscosities, powder packing densities and binder/powder reactivity is studied. Penetration of binder droplets into powder bed is also assessed. The role of organic thickeners as shape control agents is explored.

Study of printability and deformation of earth-based materials

This project aims at understanding the influence of the printing parameters (e.g. extrusion speed, displacement speed, and printing height) on the printability and drying deformation (i.e. shrinkage) of earth-based materials. The deformations of printed earth are digitally imaged and the drying kinetics are analyzed for various layer geometries over time.

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