Improving PEG confinement in smart aggregates for lime-based mortars

The implementation of polymer-based Phase Change Materials (PCMs) as functional sustainable aggregates in lime-based mortars has proven to be a viable solution to give a higher thermal performance to historical buildings in the Mediterranean region. To this purpose, PEG-1000 has been selected and used for the impregnation of porous Lecce stone aggregates. However, the inclusion of such impregnated aggregates leads to a drastic reduction of the mechanical properties of the lime-based mortars. The reason behind this reduction may be related both to a lack of compatibility among impregnated aggregates and binder, and to a pour confinement of PEG-1000. These aspects are investigated in the present work, showing that a poor confinement of the PEG- 1000 within the aggregates results into its dispersion and mixture with the binder. To prevent this, a simple coating methodology of the functional aggregate particles is proposed, based on the coverage with compatible materials. Five different types of mineral covers were tested: calcium hydroxide, milk of lime, natural hydraulic lime, cocciopesto and pozzolana. Both coated functional aggregates and derived lime mortars were analyzed with a multi-analytical approach. The overall assessment allowed to conclude that the aggregates coated with calcium hydroxide are the best performing and promising ones to confine the PEG-1000 inside the aggregates and potentially increment the mechanical properties of the mortar.