École Supérieure d'Ingénieurs des Travaux de la Construction de Metz

International audience

The field of 3D printing is in rapid evolution. The 3D printing technology applied to civil engineering is a promising advancement. From equipment and mixture design to testing methods, new developments are popping up to respond to specific demands either for the fresh or hardened state. Standardizing methods are still at an early age. For this reason, there is a multitude of 3D printers with different capabilities to print cementitious materials. In addition, norms are not applicable in 3D printing material science. Advances are being made to create new methods of testing. The key parameters of this new 3D printing process based on stratification, multiple uses of binders, and measurement at fresh and hardened states are being perfected to achieve an industrial application. This article gives an overview of how 3D-printed structures are made along with critical parameters that influence their performances. Our review suggests that the quality of the 3D prints is determined by the printing method, key printing parameters, and the mix design. We list different tests to help characterize these 3D-printed cementitious materials at the fresh state and to assess their performances at the hardened state. We aim throughout this work to give a state-of-the-art of recent advances in 3D printing technology. This could help for a better understanding of cementitious materials 3D printing for current and future related research work.

The recovery of degraded marine coasts and the improvement of natural habitats are current issues of vital importance for the development of life, both marine and terrestrial. In this sense, the immersion of artificial reefs (ARs) in the marine environment is a way to stimulate the recovery of these damaged ecosystems. But it is necessary to have a multidisciplinary approach that analyses the materials, designs and construction process of artificial reefs in order to understand their true impact on the environment. For this reason, this paper presents the manufacture of artificial reefs by 3D printing, proposing designs with a combination of prismatic and random shapes, with different external overhangs as well as inner holes. For the definition of the artificial reef designs, criteria provided by marine biologists and the results obtained from a numerical simulation with ANSYS were taken into account, with which the stability of the artificial reefs on the seabed was analysed. Three dosages of cement mortars and three dosages of geopolymer mortars were studied as impression materials. The studies included determination of the rheological properties of the mortars, to define the printability, determination of the cost of the materials used, and determination of the mechanical strength and biological receptivity in prismatic specimens that were immersed in the sea for 3 months. To evaluate the environmental impact of the materials used in the production of the mortars, a Life Cycle Assessment (LCA) was carried out. In order to choose the mortars that encompassed the best properties studied, Multi-Criteria Decision Making (MCDM) was applied and the two best mortars were used for the manufacture of the artificial reefs. Finally, the advantages and disadvantages of the 3D printing process used were analysed. The results of the studies carried out in this research show that cement mortars have better characteristics for artificial reef applications using 3D printing, and that the technique applied for the manufacture of the artificial reefs allowed the digital models to be faithfully reproduced.