Characterization, Grading and Flexural Modelling of Rubberwood (Hevea brasiliensis); for the Local and International Construction Industry

Abstract

Rubberwood, hitherto solely employed as fuel wood has found fairly suitable use in the Nigerian construction industry. This paper investigated the engineering properties of this low cost, alternative, timber material, produced from Rubber trees (Hevea brasiliensis); often employed within two weeks of felling, for the construction of formworks and related wood works. No real attempt has been made to formally grade or coordinate the properties of rubber wood as employed in the Nigerian construction industry. The research was aimed to achieve the determination of the physical and mechanical properties of naturally seasoned rubber wood obtained from the Niger Delta region of Nigeria, and assigned to it a strength/grade class. Specific properties required for grading were determined using suitable standard methods. The structural and mechanical properties of the timber wood were determined using the three point bending test in accordance with standards presented by BS EN 408 and ASTM D193, but with an aspect ratio of 12. Characteristic values for the wood properties (at the tested moisture content “MC”) were determined in accordance with BS EN 384. Adjustments were made to the characteristic values for the mechanical properties, and the density of the timber species at the test MC; to conform with the international reference MC condition of 12% (as specified by BS EN 338), and also 18% MC, to suit standards required for the Nigerian environmental condition (NCP 2). Grading was carried out in accordance with BS EN 338. The characteristic values for the mechanical properties (at 12% and 18% MC) evaluated from test results are as follows; characteristic values for MOR and MOE were 20.191 N/mm2 and 19.283 N/mm2, and 2285.784 N/mm2 and 2195.606 N/mm2 respectively. Mean values for densities (at 12% and 18% MC) were 406.169 Kg/m3 and 431.058 Kg/m3, while the characteristic values for the related densities were 338.474 Kg/m3 and 359.215 Kg/m3. Furthermore, the mean green density and characteristic green density for the rubberwood were 988.148 Kg/m3 and 900.352 Kg/m3 respectively. From the results obtained, rubberwood procured from the Niger Delta region was categorized as a grade D30 and D35 timber material at 18% MC and 12% MC respectively. Rubberwood from the Niger Delta can be conveniently employed as an alternative material to conventional timber, in both the furniture and the construction industry, but with special considerations.