Thermal properties of natural hydraulic lime-based renders with expanded perlite.

Historical buildings with highly decorated facades are common part of world heritage monuments. On the other hand, increasing demand for reduction of heating and cooling energy leads to an effort to find new thermal insulation materials compatible with the old ones. The way is to find materials with similar binder composition as those of original structures with better thermal insulation properties. In this context, the presented research is aimed at lightweight expanded perlite as a partial or full replacement of natural silica sand aggregate in rendering mixtures to improve thermal properties of final material. Basic structural, mechanical, and thermal properties of 28 days hardened renders were assessed in dependence on various volumetric substitution of silica sand. Moreover, thermal parameters were also tested in dependence on moisture content. The performed experiments proved decreased thermal conductivity and volumetric heat capacity of tested materials with expanded perlite aggregate that also significantly helped to decrease bulk density of final renders. [ABSTRACT FROM AUTHOR]