Ecological, thermal and acoustical insulating composite from hemp shives and sapropel binder

• Sapropel is suitable binder for composite with hemp shives (HS) aggregate.
• Sapropel-HS composite has good thermal insulating-acoustical properties.
• Granulometry of HS has low impact on thermal insulating-acoustical properties.
• HS composites with 40% compaction level only have good acoustical properties.
• Regression equations to predict the thermal conductivity and compressive stress are derived.

The technological parameters for the production of hemp shives (HS) composite with organic sapropel binder and reinforcement additive – paper production waste (PPW) is developed and properties of this composite are investigated in this paper. The amount of sapropel in composite was 5% of HS mass by the amount of dry materials. Thermal processing with highest temperature of 190 °C was used for hardening of the composite. The thermal conductivity and sound absorption coefficients, compressive stress, short-term water absorption, water vapor diffusion resistance factor of composite were investigated. The impact of various factors on the properties of composite was evaluated. The greatest impact has the compaction level of composite, also PPW additive. The impact of HS particles size ranging from 2.5 mm to 20 mm is much smaller. The regression equations enable prediction of thermal conductivity and compressive stress of composite depending on density and HS particles size were derived. The impact of surface hydrophobization on short-term water absorption was evaluated. Compared to HS-lime composite, better thermal and acoustic properties of HS-sapropel composite were obtained.