Influence of Hemp Shives Size on Hygro-Thermal and Mechanical Properties of a Hemp-Lime Composite

Abstract

Different fractions of hemp shives are used in the mixtures of the hemp–lime composite. The market offers shives of different granulation. It depends on the type of industrial hemp and on the capabilities of decortication machines. The aim of the research presented in the article is to check differences in the mechanical and hygro-thermal properties of composites with different shives fractions. The research part of the paper presents the preparation method and investigation on hemp–lime composites. Apparent density, total porosity, thermal conductivity, capillary uptake, vapor permeability, specific heat, mass absorptivity, flexural and compressive strength were examined. The results confirm that the shives fraction influences the individual properties of the composites. Hemp–lime composites with fine shives are characterized by higher water absorption, thermal conductivity, mechanical strength, vapor permeability as well as lower capillary-lifting capacity and specific heat than composites with thick shives.

Influence of the Direction of Mixture Compaction on the Selected Properties of a Hemp-Lime Composite

“…The article presents research on the hemp-lime composites prepared according to two recipes differing in the type (size) of hemp shives. The difference in the basic properties of these composites was demonstrated in another own work [ 16 ], while this paper presents the influence of the direction of the mixture compaction on selected parameters of composites, such as thermal conductivity, capillary rise, as well as flexural and compressive strengths. Additionally, a simulation of temperature distribution in various variants of external walls constructed using these composites was performed in the THERM 7.4 program.…”

“…The shives used are shown in Figure 1 . The average length of the shives is 2.7 mm and 8.4 mm; the maximum length for a representative sample of shives is 11.8 mm (FHS—composite containing fine shives) and 47.4 mm (THS—composite containing thick shives) [ 16 ]. The described recipes ( Table 1 ) were also used in another own research [ 16 ].…”

“…Hemp shives constitute the aggregate used in the composite. Different sizes of shives are used, for example a thickness of 0.063–8 mm and a length of 2.33–7.42 mm [ 12 , 13 ]; length 0–5 mm and 0–20 mm [ 14 ]; length 2.5–5.0 mm [ 15 ], as well as 2.7 mm and 8.4 mm [ 16 ]. The size of the shives affects the properties of the composite.…”

“…The size of the shives affects the properties of the composite. Fine fractions cause a greater demand for a binder, which results in increases in density, strength, and thermal conductivity [ 12 , 13 , 16 ]. Longer shives, in turn, have a positive effect on the flexural strength of the composite [ 16 ].…”

“…Fine fractions cause a greater demand for a binder, which results in increases in density, strength, and thermal conductivity [ 12 , 13 , 16 ]. Longer shives, in turn, have a positive effect on the flexural strength of the composite [ 16 ]. The finer the shives fractions, the easier and faster the hemp-lime mixture is homogenized during mixing.…”