Evaluation of physical and mechanical parameters in commercial NHL-based green plaster for the preservation of historical buildings.

The need to develop products for the conservation of the architectural heritage, in particular binders for plasters, is increased nowadays and those products are required to be in line with green production system and materials in full compliance with current environmental sustainability criteria. It has already been established that Natural Hydraulic Lime (NHL) is a good material for restoration; it is compatible with ancient materials and respect the environmental requirements. The use of green technologies often involves the partial use of environmental low impact materials that do not always find practical use in restoration. The starting point of the research is the selection and study of NHL-based commercial plasters used for the conservation of historic masonries and their optimization through additives cement-free in order to create green products for applications in the conservative restoration of historical heritage. The six different types of formulations chosen for this work has been evaluated and analyzed from a physical and mechanical point of view, through dynamic elastic module, compression and flexion tests, porosity and density analysis. During the execution of the research, the focus was on the effect of microstructural features of porous material, investigated in laboratory with porosimetry test as they are fundamental parameters for studying compatibility with pre-existing materials and durability over time.