Pore structure and carbonation of hydrated lime mortar with mussel shell aggregate

Abstract

Galician “Rias” conditions enable the cultivation of excellent quality mussels, as well as extension. This leads Spain to be the third producer country on the world, just after China. The 35% of this production means 25,000 tons of mussel shell waste per year. Hence, it is necessary to find a sustainable use for this material.

The bioconstruction has been recovering the use of air lime mortars for coatings in recent years. Lime is a quite easy available material in most places and its hardening process involves the uptake of CO2 from the atmosphere. Besides the aesthetics of its finishes, the compatibility for its use in the conservation of historic buildings and its proven durability have led to increase the scientific studies with this material.

The purpose of this work is to verify pore structure and carbonation changes of air lime coating mortar when limestone sand is replaced by mussel shell sand. Hydrated commercial lime powder have been used for blended lime pastes. Reference mortar and mortars with mussel shell aggregate as a substitute for limestone aggregate at different rates: 25%, 50% and 75% have been tested. Studies show that mussel shells aggregates increase the pore volume of air lime mortar mixtures, and change their pore size distribution. A low water exchange capacity between the interior of the paste is observed. The use of mussel shell aggregate increase the presence of large pores which guarantees the entry of higher volume of CO2, positively affecting the carbonation degree at one-year age.