Proposing ultimate moisture buffering value (UMBV) for characterization of composite porous mortars

• Assessing method of the ultimate moisture buffering value is proposed.
• Classification of composite porous mortars based on UMBV is proposed.
• A series of experimental methods about adsorption of materials is set up.
• Performance comparison of WSE-based mortar with common mortar is presented.
• The relationship between thermal conductivity of WSE-based mortar and moisture content is analyzed.

This paper proposes the use of ultimate moisture buffering value (UMBV) for characterization of composite materials. The evaluation of mortars includes a series of experimental methods assessing the microstructure, adsorption/desorption performance, thermal conductivity, moisture buffering value (MBV), damp condensation on surfaces and the mouldy response of mortar. In this study, common cement mortar (CM) and WSE (wood fibre, sepiolite and expanded perlite)-based mortar (WM), are moulded as a set of contrastive specimens for these tests. The results show that the adsorption of mortar is related to the performance of raw materials and internal pore structure of mortar, thermal conductivity can be influenced by moisture content of the mortar, materials with high water adsorbing capacity is liable to damp and mildew, and 20 mm is the effective thickness to indoor plastering of mortar. Adsorption, moisture proofing and desorption capacity were tested separately to evaluate UMBV of specimens. According to the tested values of these indoor walling materials, the mortar materials were classified into five grades: Ideal, Friendly, Good (but easily infested with moulds), Moderate and Inoperative. UMBV provides a comprehensive hygroscopic characterization of mortars responses to environmental conditions in realistic indoor application of these materials in sub-tropics. The evaluation method of UMBV for porous mortars can play a guiding function in setting boundary conditions of indoor humidity environmental simulation.