Effects of mussel shell aggregates on hygric behaviour of air lime mortar at different ages

Mussel shells, composed of calcium carbonate (>95%) and organic matter, are suitable alternatives to conventional sand in mortar. In addition, the use of lime instead of cement as a binder has also been considered for sustainable construction materials as well as in restorative applications. This study aims to contribute to the knowledge of air lime mortar through the analysis of the water transport properties of air lime mortar produced with mussel shell aggregates at different ages. Four mortar groups were obtained from the reference mortar by replacing limestone sand with mussel shell sand at substitution rates of 25%, 50%, and 75%. Water absorption, capillary uptake, weight variation, and drying from the fresh state up till one and two years were determined. The organic matter content and flaky seashell shape are responsible for the main differences observed between the mussel mortars and reference mortar. These two characteristics promote transport tortuosity paths and hydrophobic behaviour leading to reduced capillary uptake and increased drying resistance index. Furthermore, they enhance water retention, which increases the carbonation rate. (C) 2020 Elsevier Ltd. All rights reserved.