Title: PRESERVATION IMPACT: CHROMATED COPPER ARSENATE TREATMENT AND ITS INFLUENCE ON FLEXURAL AND SHEAR PROPERTIES OF GLUE LAMINATED EUCALYPTUS GRANDIS
Authors: Ahamada Zziwa, Allen Kyolaba Nabacwa, Simon Kizito and Agatha Syofuna
Abstract: This study examined the impact of Chromated Copper Arsenate (CCA) preservative treatment on specific mechanical properties of glue-laminated Eucalyptus grandis wood. Prior to glulam specimen preparation, wood with moisture content (MC) below fiber saturation (25±5%) underwent CCA pressure impregnation using the full Cell method. During impregnation, timber ends were sealed with PVC gel to restrict end penetration. Post-treatment, timbers were air-dried for a week, then kiln-dried to 10±3% MC, yielding an average preservative penetration and retention of 17.5±2 mm (62%­78%) and 181±11 kgm-3, respectively. Test specimens were prepared and evaluated for Modulus of Elasticity [MOE], Modulus of Rupture [MOR], and shear strength following ASTM D198 and BS373 using a Universal Testing Machine at the Department of Forestry Biodiversity and Tourism Wood Testing laboratory. Delamination percentage was assessed using the soaking delamination test. Each test employed 20 replicates, with untreated samples serving as controls. Levene’s test was used to analyze flexural properties (MOE and MOR), and one-way ANOVA was used to assess shear properties at a 95% significance level. Results indicated a 19.1% and 13.3% decrease in MOE and MOR, respectively, for treated glulam samples. Shear strength properties also declined by 3.3%. However, no delamination occurred in any glulams. Treated wood glulams exhibited lower MOE, MOR, and shear strength compared to untreated glulams, with no significant differences in strength properties observed. It is recommended that glulams from CCA-treated Eucalyptus grandis be avoided for high structural applications but could be suitable for lightweight construction projects.
Keywords: Eucalyptus Grandis, CCA preservation, Glulams, strength properties, MOE, MOR, Shear strength
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