Assessment of the effect of board density and species on dimensional stability of exatic hardwood-based cement-bonded flake boards

Abstract

Homogenous cement-bonded flake-boards were made from exotic plantation hardwood species (Gmelina arborea and Leucaena leucocephala) and the combination of the two species at equal weight ratio. Flake-boards were produced from each of the raw materials at three density levels of 1000 kg/m3, 1100 kg/m3 and 1200 kg/m3, one level of cement-wood mixing ratio of 2.0:1.0 and CaCl2 additive concentration of 1.5%. The variation in wood density, board density and the combination of the two species affected the dimensional stability of the boards. Flake-boards from the combination of the two species were more stable in thickness than other boards from the individual wood species. On the whole, boards made from Gmelina absorbed less water than other boards. However, the two wood species were found to be suitable for flake-boards production when combined with cement. The cement content, wood density, board density actually controlled the moisture responses of the boards. As the board density increased, the boards produced are dimensionally stable even at prolonged immersion in water. The thickness swelling obtained for Gmelina-board (G-board) after 24 hours soaking ranged between 4.55% and 5.17%, while the values for Leucaena- board (L-board) ranged between 4.47% and 5.84%. The value for board made from the mixture of Gmelina and Leucaena-board (G + L - board) was between 3.13% and 4.01%. The swelling after 48 hours immersion ranged between 5.25% and 6.69% for G-board, 6.04% and 7.25% for L-board and for the G + L board, the values range from 4.03% to 4.53%. The water absorption after 24 hours immersion ranged from 21.88% to 28.31% for G-board; 24.77% to 28.73% for L-board and 23.55% to 28.47% for G + L board. The values after 48 hours immersion in water were 24.90% to 32.14%, 26.26% to 32.55% and 25.61% to 32.31% respectively for the boards..

Keywords: Board Density, Flake-board, Dimensional Stability, Cement-bonded, Hardwood Species

Ghana Journal of Forestry Vol. 17 &1 81 2005: pp. 36-43