Computational Design of Biocompatible Mortar for Ericaria Amentacea Habitat Restoration: Enhancing the Ecological Value of Coastal Structures

On the Ligurian coast (Italy), 3D-printed concrete units were deployed to promote the attachment and growth of Ericaria amentacea, a habitat-forming macroalga essential for biodiversity and carbon sequestration. Although these structures were succesfully colonized in both laboratory and field settings, their mechanical resistance proved insufficient under marine loading conditions, limiting their long-term applicability. In this context, the study developed alternative mortars using conventional fabrication methods, incorporating crushed seashells as a partial replacement for natural fine aggregate. The results show that shell-based mixtures maintain flexural strength while exhibiting lower air permeability and reduced capillary absorption coefficients—properties favorable for durability in marine environments. A computational design stage was also introduced to optimize the geometry of the units with respect to linear-elastic stiffness, while enforcing the biologically inspired surface inclination for algal settlement. This approach integrates biological and mechanical criteria and points toward more resilient designs under marine stresses, offering a scalable pathway for restoring E. amentacea habitats in the Mediterranean.