Development of sustainable gypsum biocomposites upcycling mussel shells: an ecological alternative for green construction

Abstract

In recent years, the increasing focus on environmental sustainability resulted in the adoption of strategies increasingly geared towards reducing the environmental impact of building materials, in line with the European Green Deal, Agenda 2030, and the principles of the circular economy. In this context, construction is one of the main areas for action, as it is responsible for a high consumption of natural resources and the production of a considerable amount of waste. In response to these challenges, European and national regulations promote the reuse of waste materials and the adoption of Minimum Environmental Criteria (MEC), which incentivise the use of sustainable and low environmental impact materials in the construction sector. To mitigate climate change and boost green innovation in construction this study discusses the development of innovative and environmentally friendly gypsum mortars, in which the traditional sand aggregate is completely replaced by mussel shells, a by-product of the fishing and canning industry. The proposed solution offers a dual opportunity: on the one hand, it contributes to the reduction of the environmental impact linked to the disposal of this waste, which is often destined for landfills and potentially dangerous for its organic charge; on the other hand, it allows for a reduction in the harvesting of natural sand, an increasingly scarce resource that is subject to restrictions for sustainable use. The experimental activity was divided into three main phases. Initially, a physic-chemical characterisation of the mussel shells was performed to assess their compatibility with the gypsum-based binder and evaluate their potential. Subsequently, four mortar mixtures were prepared: two containing mussel shells with grain sizes of 0.00-1.00 mm and 0.00-4.00 mm and two reference mixtures with sand having the same grain size distribution. Production was carried out under standard environmental conditions (20 °C, 65% RH), which can be easily replicated on an industrial scale for practical applications. Finally, workability tests, mechanical tests of flexural and compressive strength, and thermal conductivity measurements were performed to assess the engineering performance of the mortars. Preliminary results suggest that mussel shells can be reused as a valid alternative to traditional (commercial) aggregate and can offer competitive performance with respect to traditional mortars, with advantages in terms of lightness and thermal insulation, as well as lower environmental impact. Furthermore, the reuse of waste from the food industry perfectly aligns with the principles of the circular economy, promoting the valorisation of waste materials in new production cycles and reducing dependence on virgin raw materials. The integration of secondary materials in construction represents a concrete strategy to achieve the SDGs and MEC compliance, favouring the use of products with a lower environmental impact and improving resource efficiency. In particular, the use of these gypsum mortars with alternative natural aggregates can be an efficient solution for the production of environmentally friendly plasters, contributing to the transition towards more sustainable and responsible building.