Thermo-physical, mechanical and microstructural properties of cementless lightweight mortar

In this work, an eco-friendly lightweight cementless mortar has been prepared primarily from natural resources and industrial solid wastes. Lime–silica fume (lime–SF) paste (1 : 1 wt) was used as a green binder in lieu of cement. The binder was combined with expanded perlite (EP) aggregate with various aggregate volume contents of 25, 50 and 75%. The compressive strength, indirect tensile strength, bulk density, thermal conductivity, thermal diffusivity and solar reflectivity of the hardened mortars were determined at 28 d of curing. Thermogravimetric analysis (TGA) was used to assess the phase composition. The durability of the developed mortars was estimated with an accelerated aging test. The results showed that the newly developed mortar possesses reasonable mechanical performance, reduced thermal conductivity and enhanced solar reflectivity. The increased porosity of EP-blended mortar facilitates water migration within the hardened structure, leading to remarkable enhancement in resistance to wetting/drying aging conditions and hence improved durability. TGA patterns revealed a phase composition similar to that of the hydrated cement. Scanning electron microscopy showed that good bonding exists between the hardened lime–pozzolan matrix and EP aggregate. The lightweight mortar developed can be highly recommended for plastering and rendering applications in sustainable and energy-efficient buildings.