A comparison between low-clinker cement and geopolymer mortars for their application in 3 D printing is discussed in this paper. The mortars are composed of materials with low environmental impact, such as cements with low clinker content, by-products of the industry and recycled aggregates. The developed mortars were both mechanically and rheologically characterized. The environmental impact was studied by LCA. To select the most suitable dosages, MCDM analysis was applied based on cost of materials, printability and LCA. Compressive strength was considered as a normalizing parameter for both the LCA and cost. The mortars showed good printability and suitable mechanical strength, being higher in the cement mortars. The LCA showed that the geopolymer mortars have a higher environmental impact due to the use of sodium hydroxide. Likewise, MCDM revealed that low-clinker cement mortars are at the top of the ranking, due to a lower environmental impact and lower cost of materials.

This paper deals with the evolution monitoring of biomass colonization and mechanical properties of 3D printed eco-materials/mortars immersed in the sea. Measurements of tensile strength, compressive strength, and Young’s modulus were determined on samples deployed along the Atlantic coast of Europe, in France, United Kingdom, Spain, and Portugal. The samples were manufactured using 3D printing, where six mix designs with a low environmental impact binder were used. These mortars were based on geopolymer and cementitious binders (Cement CEM III), in which sand is replaced by three types of recycled sand, including glass, seashell, and limestone by 30%, 50%, and 100% respectively. The colonization of concrete samples by micro/macro-organisms and their durability were also evaluated after 1, 3, 6, 12, and 24 months of immersion. The results showed that both biomass colonization and mechanical properties were better with CEM III compared to geopolymer-based compositions. Therefore, the mixed design optimized according to mechanical properties show that the use of CEM III should be preferred over these geopolymer binders in 3D printed concrete for artificial reef applications.