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The present research investigated bio-based construction material based on hemp shives and gypsum. Low-density material was developed with densities of 200, 300, and 400 kg/m3. Simple yet robust production technology was used. For the first time, a binder for biocomposites obtained from phosphogypsum was used and properties were compared to commercial gypsum. CO2 negative building material was developed with up to 92 kg CO2 ekv./m3 entrapped. Both physical and mechanical properties were studied. Thermal conductivity was in the range from 0.058 to 0.101 W/(m·K) and compressive strength from 0.10 to 0.57 MPa. Biodeterioration test results showed that the pH of 5.60–6.55 for biocomposites promoted a rapid mold growth. Mold growth was slightly lower for composites with higher gypsum content, while phosphogypsum induced more rapid mold growth. Cladosporium, Rhizopus, Chaetomium, and other molds were observed on samples even at an early stage of testing giving a serious concern about only limited application in dry conditions for such gypsum-based biocomposite. [ABSTRACT FROM AUTHOR]

This study investigated the effect of phenol-formaldehyde (PF) resin treatment on the dimensional stability of birch solid wood and plywood. Therefore, three different low molecular weight PF resins with average molecular weights (Mw) of 292, 528, and 884 g/mol were synthesized and used for silver birch (Betula pendula) solid wood (20 × 20 × 20 mm3) and veneer (100 × 100 × 1.4 and 300 × 300 × 1.4 mm3) impregnation to produce plywood. The weight percent gain (WPG) and bulking after curing of resin treated wood specimens were determined. The leaching was performed to evaluate the PF resin fixation stability. All tested resins at all concentrations were similarly fixed in wood blocks after the leaching (1.5–2.0% WPG loss). The dimensional stability of birch wood after treatment with all tested PF resins was significantly improved. The anti-swelling efficiency (ASE) of birch wood blocks treated with PF resins after seven water soaking-drying cycles was in the range of 39–53%, 46–65% and 49–65% using 10, 15 and 20% solution concentrations, respectively. Whereas, the ASE of plywood obtained from veneers treated with 10% of PF solution was improved by 6–20%. The equilibrium moisture content (EMC) and volumetric swelling (VS) of PF treated plywood at 98% of relative humidity (RH) decreased significantly. All PF resin treated plywood surfaces were more hydrophobic compared to untreated plywood. [ABSTRACT FROM AUTHOR]