Influence of compaction direction on selected thermal and moisture properties of a lightweight composite based on magnesium binder and organic filler

Abstract

An alternative binder in thermal insulation composites based on hemp shives is magnesium cement. It provides higher mechanical strength of the composite in comparison to the lime binder. Thanks to this, it is possible to reduce the amount of binder in relation to the shives, and as a result, obtain a lower density and better thermal insulation parameters. The process of compacting the composite mixture determines many of its properties. The longitudinal shape of the shives causes that during compaction they are arranged mainly perpendicular to the direction of compaction. The unidirectional course of the fibers in the shives determines the anisotropic nature of both the shives and the composite. The article presents the results of tests of thermal conductivity and capillary rise of the compacted composite in the direction perpendicular and parallel to the heat flux and moisture transport. A composite with a low binder content, characterized by a density of about 250 kg/m3, was tested. The direction of the mix compaction had an impact on the differences in the obtained results. This phenomenon can be used, for example, in the production of blocks or other prefabricated elements, using the appropriate direction of compaction depending on the expected properties and applications of the composite.