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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]

In this study, mould and blue stain susceptibility, capillary water uptake (CWU) and microstructural properties of two thermo-hydro-treated (THT) birch plywood products A and B were investigated. Plywood A represented a THT industrial plywood glued with a phenol formaldehyde (PF) adhesive. Plywood B represented panels from THT veneers glued with a PF film. The THT regimes were (temperature, °C/time, min): 150/10, 150/50, 160/10 and 160/50. Both THT plywood products and untreated samples were resistant to mould and blue stain growth in 1 month of exposure in laboratory and outdoor conditions. A statistically significant correlation between fungal growth in laboratory and outdoor conditions for plywood products A and B was not found (P > .05). Artificial weathering of both plywood products provided adverse fungal growth results compared to the natural weathering test outdoors. The fungal growth on plywood A and B samples mutually strongly correlated (P < .05) only in the outdoor test. Plywood B samples demonstrated a much lower CWU than plywood A, obviously because of microstructural changes, including densification, and type of glue used. Lower CWU of THT plywood in comparison with untreated samples did not provide clear evidence on inhibition of fungal growth. [ABSTRACT FROM AUTHOR]

A study of self-binding fibreboards pressed without synthetic adhesives is reported. The board samples of steam-exploded grey alder (Alnus incanaL. Moench) particles hot-pressed under a variety of conditions including moisture content of the mat (8% and 12%), temperature (150°C, 160°C, 170°C and 180°C) and pressure (0.2–8 MPa) are tested for moisture resistance (standard EN 1087-1), decay resistance (standard ENV 12038) and reaction to fire performance (ISO 5660-1). The moisture resistance of the board samples is found to satisfy the standard EN 622-5 for load-bearing medium-density fibreboard for use in humid conditions (MDF.HLS). The tested board samples are not fully resistant to theTrametes versicolorfungus, the mass loss of specimens exceeding 3%. Reaction to fire performance of the self-binding board evaluated by the average rate of heat emission being by about 25% higher is worse compared with MDF.HLS. [ABSTRACT FROM AUTHOR]