Tree bark utilization in insulating bio‐aggregates: a review

Abstract

This review gives an overview of recent advances in research on the role of tree bark material in bark-cement bio-composites, and their potential as building insulation materials. Suberin and other bark extractives seem to be of great importance for the insulation properties of such composites. Bark is a readily available, biological raw material with unique properties and it has revealed promising results as a bio-insulation material, either alone or in mixtures with different matrices (cement, lime, resins, polymers, etc.). The thermal, mechanical, acoustic, and hygroscopic properties of these bark-insulating composites depend on several factors, primarily the type of tree bark, the density and mechanical strength of the bark, the density of the boards produced, and the ratio of bark material to the binder material used in the board production (cement, lime, resins, polymers, etc.). The size of granules and the thickness of the board produced seem to be factors with a lower impact on the properties of the bark-cement composites. A low proportion of bark fibers or particles (0.5-1%) in bark-cement composites has proven highly beneficial to their mechanical and thermal properties and ensures higher workability of the mixture. Different modification treatments of bark material should be investigated, with the aim of decreasing the bark extractives content, to improving the cement setting, decreasing the unstable hemicellulose components and their hygroscopic nature, improving the bark particles' durability in alkaline environments, and upgrading their adherence properties. As the demand for alternative, sustainable structural materials keeps rising, the cement-bark composites will undoubtedly keep attracting the attention of the scientific and industrial world.

Fire Retardancy of Cementitious Panels with Larch and Spruce Bark as Bio-Admixtures

“…A number of results are clearly above the average. However, the IB of the specimens is generally very low, but represents a characteristic of mineral-bonded bio-aggregates [ 13 , 15 ].…”

“…There is no correlation (R 2 = 0.06) between the density and the fire resistance duration ( Figure 13 ). The assumption is that panels with higher densities have a higher cement content (>40%) and therefore more fire-retardant material is available [ 15 ].…”

“…Flame-retardant additives have been extensively investigated for construction materials [ 10 , 11 ] as substances that impede the fire propagation in a material [ 12 ]. The adjoining of clay [ 13 ] and cement [ 14 , 15 ] in lignocellulosic composites can contribute to the fireproof properties due to the effects of reducing heat transfer and catalyzing the char development from cellulose due to the metal ions included in the chemical composition of these materials [ 5 ]. Cement bound wood-wool panels have been on the construction market since the beginning of 20th century [ 16 ].…”

Chemical Composition and Related Properties of Lime (Tilia cordata Mill.) Bark and Wood as Affected by Tree Growth Conditions

“…Bark is a valuable raw material for the pharmaceutical and cosmetics industries, as a source of fuel, or in horticulture as a substrate for composting [ 9 ]. The role of bark as a biocomposite in the production of insulation materials was extensively discussed in a review paper by Gianntos et al [ 10 ]. The applicability of bark in biomonitoring was indicated by Kosiorek et al [ 11 ], Krutul et al [ 12 ] and Pavlović et al [ 13 ].…”

Selected Properties of Cement Bound Spruce and Larch Bark Bio-Aggregates

“…Bark is a by-product of the wood industry and is widely available [19] at a low cost. Bark is the external protective tissue that surrounds the vascular cambium zone of trees and possesses various functions [20]. Among them can be count protection of plant stems, aeration of stems in some species, water storage, sap transport, and mechanical support for tree stems [21].…”