Influence of depoisoning strategies on mechanical properties of wood-cement composites.

VICTORIO MARZOCHI; ANALIA QUIROGA; ALFREDO MARCIPAR; IGNACIO RINTOUL

Buenos Aires, Argentina

Congreso; 9 Congreso Internacional SAM-CONAMET; 2009

Departamento Materiales CAC-CNEA e Instituto Sabato CNEA-UNSAM

Selected for oral presentation. Wood-cement composites are promising materials for structural and isolation purposes. Durability, toughness, high dimensional stability, resistance to environmental and biological degradation and economic factors are features that can be exploited in a variety of construction and housing applications. However, the wood cement incompatibility due to the poisoning effect of wood-sugars on cement setting and the lack of knowledge about this effect in national woods and cements impairs the adoption of these composites at industrial scale. Several technological strategies have been developed for wood depoisoning: extraction, degradation and retention of poisons. In general, those treatments permit correct cement setting on wood surfaces but diminishing the mechanical properties of resulting materials. This work evaluates the depoisoning efficiency of the extraction in water method, poison degradation by alkaline hydrolysis and poison retention by several surface treatments. Tensile properties of individual wood particles and cement bonded wood particles and compression properties of wood-cement boards were studied. Microscopy of treated and fractured wood and wood-cement surfaces are also included. Caroline Poplar harvested in the Argentinean Litoral coming from residues of local wood industry and commercially available Portland cement were selected as case materials. Data analysis was performed using experimental designs based on response surface methods. The most effective depoisoning treatment resulted alkaline hydrolysis followed by the retention and extraction methods. Retention method resulted in an increment of the tensile properties of individual wood particles and decrease of cement bonded particles. Extended degradation of wood sugars and short chain length polysaccharides by alkaline hydrolysis is proposed as explanation. Inhomogeneities of the surface treatment in a very irregular surface such as wood surface and partial extraction of polysaccharides which afterwards decompose in individual sugar molecules during cement setting are proposed as explanation for less efficient depoisoning of the retention and extraction methods.