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

Abstract

The aim of this study is to investigate the suitability of spruce and larch bark for the production of cement-bonded composites. At the beginning of this research, the curing behaviour of the admixtures was quantified with temperature profiles when testing spruce, larch, pine and poplar bark, to determine the compatibility between the components of the bio-aggregates, to analyse the cement curing and to establish which bark species should be successfully included in cement bonded composites. Considering the results, it was observed that the average densities of 600–700 kg/m3 of bio-aggregates are 40–55% lower than that of established products on the market, although spruce and larch bark are in a similar range. The situation is different for the compressive strength, as larch bark showed up to 30% higher values than spruce bark. This study revealed also different hardening characteristics of the two cement types used as binders for spruce and larch bark. The results of this study demonstrated that tree bark of Picea abies and Larix decidua Mill. can be successfully utilized for the production of a cement-bonded composite material.

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

“…IB is strongly related to particle distribution, bonding and compaction inside the panels [ 14 ], but can also be caused by incorrect or incomplete curing of the cement [ 45 ]. In case of specimens with spruce bark, the low IB can be attributed to incomplete curing of the cement, in some cases the specimens failed even without the application of force during the test preparation ( Figure 5 right).…”

“…The test specimens were porous, this resulted in an inhomogeneous bond between the bark fractions and the cement [ 47 ], which is also reflected in the low IB, especially of samples from TG2-L HP. The pressing method could also have a significant influence, the samples compacted with HP showed lower values compared to the compaction using SC [ 14 ]. It is possible that too much pressure during pressing is not necessary and reduces the panel properties.…”

“…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 ].…”

“…As a by-product of wood processing industry, tree bark has an enormous potential in applications as adhesive filler to reduce formaldehyde emissions [ 18 ], thermal [ 19 , 20 ] and acoustic insulations [ 21 ], as raw materials for MDF [ 22 ], particleboard [ 23 ], pellets [ 24 ] or for medicinal purposes [ 25 ]. The combination between tree bark and cement results in lightweight concrete composites with densities around 800 kg/m 3 [ 14 ]. Wood and tree bark, due to hemicelluloses, starches, sugars, phenols and acids, tend to hinder cement hydration in composite, resulting in longer setting time and a limitation in the strength of material, as a consequence of micro-fracturing of the matrix during cement hydration [ 26 , 27 ].…”

“…It was found that the addition of magnesium chloride and sodium silicate significantly improved the hydration behavior of materials and, in some cases, of the compressive strength. Urstöger et al [ 14 ] examined the compressive strength and hydration behavior of composites with spruce and larch bark bounded with cement for lightweight composites and emphasized the larch bark influence on composite properties, especially in cold pressing system. This research is a follow-up of [ 14 ] and deals with the flammability analysis of cement bound larch and spruce bark composite panels, besides recycled material from previous experimental trials.…”