Influence of the spruce strands hygroscopic behaviour on the performances of wood-cement composites

Abstract

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Investigation of local degradation in wood stands and its effect on cement wood composites

“…The popularity of this building material is mainly related to the increasing concerns about sustainability in the building industry [3]: Natural fibres are not expensive and have lightweight, nontoxic and biodegradable properties which lead to many applications as replacement of synthetic fibres [4]. One commonly used composite is the wood wool cement board (also called Excelsior board, WWCB), produced using Spruce (Picea Abis) wood wool strands, white cement and chemical additives and characterized by a high wood/cement ratio (0.4-0.6) [1,5,6]. Having a thickness between 50 and 150 mm, WWCBs are mainly applied as ceiling tiles for acoustic insulation, but they also have good acoustic properties and durability against fungi thanks to the fibre mineralization [1,2,7].…”

Reinforcing Mechanisms of Coir Fibers in Light-Weight Aggregate Concrete

“…This is caused by the heterogeneity of fibers and cement resulting in weak ITZs, which are in favor of cracks propagating. Another explanation can be the desiccation shrinkage of fibers since fibers are saturated with water which may be taken up by cement for further hydration [ 25 , 61 ]. However, the ITZs formed with the pretreated fibers are much denser and less cracked, and a better solid bonding can be seen.…”

“…Primarily, some constituents of coir fibers such as hemicellulose can be easily decomposed into various sugars under the alkaline environment in cement, which can affect the cement hydration kinetics [ 22 , 23 ]. Secondly, coir fibers are hydrophilic and thus their high moisture absorption can cause competitive water absorption with cement, thereby affecting the available water amount for cement hydration [ 24 , 25 ]. Saturated fibers can be used to take advantage of this feature, thus, extra water can be entrained in the cement system for internal curing [ 26 ].…”

Aditivos químicos em compósitos de gesso-madeira pré-tratados ou não com suspensão de hidróxido de cálcio

“…A partir da análise estatística realizada, observouse que, ao considerar o pré-tratamento utilizado, os compósitos produzidos com a suspensão de cal apresentaram redução significativa da resistência à tração na flexão. Isto pode ter ocorrido pelo fato de que a maior disponibilidade de água proporcionada pelo prétratamento contribui para o aumento da porosidade e, consequentemente, para a diminuição do desempenho mecânico (KUMAR, BHATTACHARJEE, 2003;CAPRAI et al, 2018). Outros pesquisadores sugerem, ainda, que partículas amolecidas tendem a enfraquecer sua ligação com a matriz (ONUAGULUCHI, BANTHIA, 2016).…”

“…Assim como explicada anteriormente, a diminuição da resistência observada para os compósitos produzidos com a serragem pré-tratada pode ter sido influenciada pela maior disponibilidade de água que contribuiu para o aumento da porosidade e para a diminuição do desempenho mecânico (KUMAR, BHATTACHARJEE, 2003;CAPRAI et al, 2018;USMAN et al, 2018). Considera-se, ainda, que além das partículas amolecidas propiciarem o enfraquecimento da ligação com a matriz (ONUAGULUCHI, BANTHIA, 2016), os diferentes processos de hidratação dos dois aglomerantes presentes nos compósitos podem influenciar no desempenho (AIGBOMIAN, FAN, 2013).…”