Exploring the potential of soft calcite: innovative solutions for sustainable engineering

The sustainable use of resources is a key issue in a global trend where the demand for them increases exponentially to support ongoing economic and social growth. This requires new strategies that must focus on transforming waste into recycled products for other applications. Inspired by the circular economy concept, this approach can be extended to different fields, including the management and reuse of marine wastes like sediments, periodically dredged in port areas (in Europe about 100-200 million m3/year), or seafood industry wastes (reached a production record of 214 million tonnes in 2020) [1]. Europe is the second worldwide bivalve producer and discarded shells represent more than half of the fish-product mass, with high disposal costs and considerable environmental impacts. A proper valorization of its residues would decrease the ocean contamination and improve the sustainable management of marine resources. In line with these concepts, we are exploring the potential of mussel shells waste as a valuable raw material to be biorefined and added to marine sediments, to find out novel eco-friendly solutions that can be used in construction for a sustainable engineering. Improving an existing protocol [2], this contribution explores the intriguing properties of a peculiar form of calcium carbonate, known as “soft calcite”, obtained from Mediterranean mussel shells by controlled dissolution of the aragonite component. This material proved to possess a high specific surface, as shown by morphological analyses, resulting in interesting adsorption capability and can be used as a substitute for other high impact and non-renewable materials, for example in building materials. Heat treated mussel shells reduced into fine powder are already used as partial substitute for binders to mechanically and/or chemically stabilize fine grained marine sediments [3]. Here we propose the mixing of the dredged sediments in their natural state with different amounts of hydraulic binders and soft calcite powder, that partially replaces the binder in the mixture, to obtain new building materials with good mechanical properties. [1] FAO. The State of World Fisheries and Aquaculture 2022. Towards Blue Transformation. Rome, (2022) [2] J. N. Murphy, C. M. Schneider, K. Hawboldt and F. M. Kerton, Matter 3, 6 (2020) 2029-2041 [3] R. Petti, C. Vitone, M. I. Marchi, M. Plötze and A. Puzrin, Géotechnique (2024) 1-20