This work physically, mechanically, and chemically characterized the composites produced from Portland CP II-E32 cement and fresh Indian cedar wood particles previously treated by immersion in hot and cold water. Density values for wood particulate composites were around 50% lower compared with the wood-free control treatment, from 0.88 to 1.78 g/cm³. A larger swelling was observed for the composite material. The results of compressive strength and stiffness indicated that there is no need for particle treatment for composite production. Hot and cold water immersion treatments reduced the total Indian cedar wood extractives by 33% and 42%, respectively. Optical microscopy analysis was used to identify adhesion failures between the cement/wood interface of the composite produced with fresh particles, which presented a higher percentage of extractives. This result indicated that the greater concentration of total extractives partially inhibits the matrix-matrix interaction reinforcement. Despite the reduction in total extractives caused by the treatments, this process is not necessary for the composite production because there is no statistical difference between the treatments. The values obtained for the composite indicate the possibility of application in sealing blocks in light construction systems.
Cement-based composites with lignocellulosic residues (e.g. wheat straw, rice husk, and bagasse) as fillers have reduced density and cost. Pretreatments have been applied in these raw materials to improve their compatibility with cement. This work aimed to characterize composites made from cement and wheat straw particles that had been chemically treated (2% NaOH solution) at two different temperatures (30 °C and 60 °C). Values of bulk density (209 kg·m-3) and specific density (679 kg·m-3) were determined for wheat straw at 12% moisture content. Straw yield was 71.9% and the particle size distribution showed large concentrations of wheat straw particulate material between 5- to 10-mesh. Composites made with wheat straw particles, in comparison to the control treatment, showed half the density, i.e., from 1800 to 900 kg·m-3. Also, the stress x strain curve presented a higher deformation before failure. NaOH pretreatment did not affect the mechanical properties of wheat straw composites.
The glued laminated timber industries in Brazil have been looking for alternatives that improve the quality of their products, by choosing the correct wood used in the composition of the structural elements, type of adhesive, as well as by monitoring the quality of the material's manufacturing process. This study evaluated the percentage of delamination and shear strength of glue lines in glulam beams constructed with Brazilian reforestation woods (pine and eucalyptus) and structural adhesives (Cascophen RS 216M and Polyurethane Jowat 686.60). For that, the Brazilian test method [1] based on the [2] was used. To qualify the percentage of failure in the gluing areas, the ImageJ software was used. Complementary microscopy analyzes were used to evaluate the gluing areas. As a result, it was observed that the best bonding quality results were obtained for pine and eucalyptus woods bonded with Cascophen RS 216M adhesive. There were no statistically significant differences between the shear strengths of the glue lines of the cross sections of the tested beams. The wood density and the adhesive viscosity had an influence on the bonding quality of glulam beams. The microscopic analyzes indicated that pine woods have an anatomical structure that allows better bonding quality.
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