Formulations de composites à base de liants basse température type géopolymère à base d'argilite et de différents renforts : réalisation d'une pièce par fabrication additive

This work is part of the Cigéo project (geological industrial disposal for radioactive wastes) and focuses on studying alternative materials for the elaboration of the lining of the high-level radioactive waste storage cells. Composites materials with inorganic matrix and reinforcements are one of the innovations being considered as an alternative to replace metallic materials in the lining. The use of geopolymers reinforced with inorganic elements could meet the desired specifications. The insertion of wollastonite and glass fibers to a geopolymer matrix allowed to control viscosity suitable for shaping by casting and additive manufacturing while ensuring the mechanical strength of the consolidated material. This allows obtaining flexural and compressive strengths going up to 101 MPa and 20 MPa, respectively. To shape the extruded solution at a half scale, a 3D printing system was then developed. A specific extrusion head has been designed and integrated into a 6-axis robotic cell. The control and identification of printing and materials parameters make it possible to control the process and to print geopolymer composite structures at half scale (ɸ = 35 cm).Ce travail s’inscrit dans le cadre du projet Cigéo (Centre industriel de stockage géologique de déchets radioactifs) et étudie des voies d’optimisation pour les chemisages des alvéoles de stockage des déchets radioactifs de haute activité (HA). Des matériaux composites à matrice et renforts inorganiques sont une des voies d’innovation envisagées en alternative aux matériaux métalliques pour la réalisation du chemisage. L’utilisation de matériaux de type géopolymères renforcés par des éléments non organiques pourrait répondre aux critères souhaités. L’ajout de wollastonite et de fibres de verre à une matrice géopolymère a tout d’abord permis de contrôler la viscosité et de l’adapter à une mise en forme par coulage ou par fabrication additive tout en assurant une tenue mécanique satisfaisante du matériau consolidé. Des résistances mécaniques en compression et en flexion allant respectivement jusqu’à 101 MPa et 20 MPa ont pu être obtenues. Pour tester la solution extrudée à l’échelle ½, un système d’impression 3D a ensuite été développé. Une tête d’extrusion spécifique a été conçue et intégrée à une cellule robotique 6 axes. Le contrôle et l’identification des paramètres d’impression et des paramètres matériaux ont finalement permis la maitrise du pilotage du procédé et l’impression de structures en composite géopolymère à l’échelle ½ (ɸ = 35 cm)

Formulation of composites based on low temperature binder, geopolymer type, based on argilite and different fillers : realisation of a peice by additive manufacturing

Ce travail s’inscrit dans le cadre du projet Cigéo (Centre industriel de stockage géologique de déchets radioactifs) et étudie des voies d’optimisation pour les chemisages des alvéoles de stockage des déchets radioactifs de haute activité (HA). Des matériaux composites à matrice et renforts inorganiques sont une des voies d’innovation envisagées en alternative aux matériaux métalliques pour la réalisation du chemisage. L’utilisation de matériaux de type géopolymères renforcés par des éléments non organiques pourrait répondre aux critères souhaités. L’ajout de wollastonite et de fibres de verre à une matrice géopolymère a tout d’abord permis de contrôler la viscosité et de l’adapter à une mise en forme par coulage ou par fabrication additive tout en assurant une tenue mécanique satisfaisante du matériau consolidé. Des résistances mécaniques en compression et en flexion allant respectivement jusqu’à 101 MPa et 20 MPa ont pu être obtenues. Pour tester la solution extrudée à l’échelle ½, un système d’impression 3D a ensuite été développé. Une tête d’extrusion spécifique a été conçue et intégrée à une cellule robotique 6 axes. Le contrôle et l’identification des paramètres d’impression et des paramètres matériaux ont finalement permis la maitrise du pilotage du procédé et l’impression de structures en composite géopolymère à l’échelle ½ (ɸ = 35 cm).This work is part of the Cigéo project (geological industrial disposal for radioactive wastes) and focuses on studying alternative materials for the elaboration of the lining of the high-level radioactive waste storage cells. Composites materials with inorganic matrix and reinforcements are one of the innovations being considered as an alternative to replace metallic materials in the lining. The use of geopolymers reinforced with inorganic elements could meet the desired specifications. The insertion of wollastonite and glass fibers to a geopolymer matrix allowed to control viscosity suitable for shaping by casting and additive manufacturing while ensuring the mechanical strength of the consolidated material. This allows obtaining flexural and compressive strengths going up to 101 MPa and 20 MPa, respectively. To shape the extruded solution at a half scale, a 3D printing system was then developed. A specific extrusion head has been designed and integrated into a 6-axis robotic cell. The control and identification of printing and materials parameters make it possible to control the process and to print geopolymer composite structures at half scale (ɸ = 35 cm)

Influence of the geopolymer formulation on the endogeneous shrinkage

International audienc

Development of geopolymer composites for the lining of high level radioactive waste

National audienc

Formulation of a geopolymer composite with mineral fillers: modification of the geopolymer viscosity and mechanical properties

International audienc

Shaping of geopolymer composites by 3D printing

International audienceThis work aims to shape a hollow cylinder with a geopolymer and an additive manufacturing process (3D printing) without organic additives. The formulation of a geopolymer composite using only mineral parts is proposed and the parameters of the 3D printing process were optimized. The mechanical properties, the microstructure, and the adhesion of the layers of the printing material were analysed and compared with the literature. The results showed that the geopolymer composite could be printed with the addition of small ratios of wollastonite, glass fibers, or non-reactive aluminosilicate and by modifying the printing speed. The stacking layers exhibited a good adhesion between them, avoiding the socalled "cold joints" effect, and the fibers are flow-oriented during the process. Some hollow cylinders are successfully printed with a flexural strength of 15 MPa

INFLUENCE OF THE WOLLASTONITE AND GLASS FIBERS ON GEOPOLYMER COMPOSITES WORKABILITY AND MECHANICAL PROPERTIES

International audienceThis work aims to synthetize geopolymer composites and study the influence of the aluminum concentration, wollastonite and glass fibers on the properties of the fresh and hardened material. To this end, different metakaolin, wollastonite and glass fibers contents were used to synthesize geopolymer composites. The effect of reinforcement elements on the geopolymerization reaction has then been studied with FTIR spectroscopy and thermal analysis (DTA-TGA). Moreover, the viscosity and the setting time of the reactive mixture, as well as the compressive strength of the hardened material, have been measured for the different compositions. The results showed that the nature of the reinforcement added induces different polycondensation reactions. The wollastonite improves the viscosity and the mechanical properties by ensuring a better dissolution of the metakaolin, whereas the glass fibers act as an anchoring site during the geopolymerization reaction, leading to a ductile failure of the material. Finally, the aluminum concentration enables to monitor the viscosity and setting time of the reactive mixture and has a significant influence on the microstructure and the compressive strength. Thus, the initial formulation of the geopolymer composites allows controlling the properties of the fresh and hardened geopolymer composites

Adaptation of the geopolymer composite formulation binder to the shaping process

International audienceThis work aims to adapt a formulation of a geopolymer composite to elaborate complex shapes. Here a hollow cylinder is chosen to investigate different possible solutions: building process according to the formulation. To this end, different content of metakaolin, wollastonite, and glass fibers was used to identify the feasibility of shaping of the geopolymer composites. Hollow cylinder shape was elaborated from different formulations by casting and additive manufacturing (robocasting or Direct Ink Writing) regarding their feasibility. The mechanical properties of the formulations were then analyzed with thermal analysis, compressive and flexural tests, and compared with their way of shaping. The results showed that the viscosity can be mainly controlled by the wollastonite content. The formulations adapted to the robocasting present an optimal mechanical resistance due to a higher amount of reinforcement elements. A formulation that can be cast and robocast has been obtained and presents a compressive strength of 89 MPa and bending strength of 15 MPa. Thus, here some keys are 2 given to design a formulation of geopolymer composite adapted to a shaping process by modifying the metakaolin, wollastonite, and glass fiber content