Blue planet: Hybrid solutions for underwater structures with seashell concrete and biorock technology

Abstract

Global sea levels are predicted to rise by up to 2 meters by 2100 due to the high rates of carbon emissions, which lead to frequent flooding, eventually making coastal cities uninhabitable (NOAA, 2022). This thesis explores how seashell waste, in combination with the process of biorock technology (mineral accretion), can be turned into a hybrid material system Furthermore, it investigates how this hybrid material be utilized for load-bearing underwater structures. Seashell concrete, derived from recycled seashell waste, is ground and calcined to replace traditional aggregates and Portland cement , reducing carbon emissions by 50% compared to traditional concrete(Crook, L., 2024). Biorock technology - a process of mineral accretion, meanwhile, uses seawater electrolysis to grow limestone, creating a material around three times stronger than traditional concrete while promoting coral reef restoration (Goreau, T.J., 2012). The material experiments test the properties of each material and the potential of hybrid material compositions. While seashell concrete alone lacks the compressive strength of traditional concrete, reinforcing it with biorock technology compensates for this weakness, potentially meeting the load-bearing requirement for underwater construction. The design proposal transforms the Montipora coral’s layered and radial form into a modular underwater experimental building prototype at Dhangethi Jetty, Maldives. Computation tools shaped the geometry and created the structure, which has helped explore coral-like forms and simulate how limestone grows through mineral accretion. This coral-inspired structure, combined with biorock technology, creates a habitat for coral polyps and transforms the building itself into a living reef. By merging this hybrid material innovation with coral reef restoration, the project offers a blueprint for future coastal cities. It demonstrates how architecture can adapt to sea level rise, reduce reliance on carbonintensive concrete, and actively rebuild ecosystems - proving that human habitats can work with and even foster marine life.