Performance of Self-Compacting Mortars Using Ground Seashells as Recycled Sand

The findings highlight the potential for broadening the use of shell aggregates in construction applications. This research investigated the viability of incorporating milled Acanthocardia tuberculata seashells as fine sand replacements for natural calcareous sand in the production of self-compacting mortar. These results highlight a promising avenue for coastal industries to reduce waste while enhancing the durability of construction materials. Mortar mixtures containing recycled seashell aggregates exhibit superior overall performance compared with those using natural sand in terms of durability, although there is a slight reduction in workability and mechanical strength. Three replacement levels of natural limestone sand (0%, 50%, and 100%) with seashell-based fine aggregates were studied, along with three different powdered/sand ratios. The fresh properties of the mixtures were assessed for workability, whereas the hardened specimens were analyzed using an X-ray technique, thermogravimetry, and differential thermal analysis. Key performance and durability properties, including compressive and flexural strengths, bulk density, porosity, water absorption, dimensional stability, and mercury intrusion porosimetry at 28 days of hardening, were also evaluated. Overall, the incorporation of Acanthocardia tuberculata seashells into cementitious materials supports the principles of the circular economy, providing both environmental and performance advantages.