Physico-chemical characterisation of plant particles with potential to produce biobased building materials

A physico-chemical characterisation of flax shiv (Linum usitatissimum), hemp shiv (Cannabis sativa L.), maize bark (Zea mays L.), miscanthus (Miscanthus), reed (Phragmites australis), rice husk (Oryza sativa), sunflower (Helianthus annuus) bark and pith and wheat (Triticum) by means of chemical composition, particle size, density and water behaviour was carried out in order to facilitate their comparison. Particle size distribution, water sorption isotherms and water absorption kinetics of the plant particles were modelled using respectively the log-normal distribution, GAB and Nagy and Vas models. Results of chemical composition (soluble compounds 6.0-38.6 g/100 g dry material (% d.b.), hemicellulose: 5.0-34.8 % d.b., cellulose: 23.3-49.0 % d.b., lignin: 3.3-41.7 % d.b., ashes: 2.4-13.7 % d.b.) highlight the heterogeneity of the studied materials. Sunflower bark showed the largest mean values for length (10.7 mm) and width (3.9 mm) hemp shiv being the smallest studied particle with 4.5 mm of length and 1.2 mm of width. The range of values of bulk density for the studied samples varied from 21 kg/m3 (sunflower pith) up to 157 kg/m3 (sunflower bark). A slight linear relationship (R2<0.87) was found between porosity and bulk density of plant particles. Water absorption kinetics were consistent with the plant chemical composition and the open porosity which highlight a fair understanding of inter-dependence of particles physical properties.