Effect of Aqueous Extraction of Wood-wool on the Properties of Wood-wool Cement Board Manufactured from Teak (Tectona grandis)

摘要

Extractives in teak (Tectona grandis) inhibit the setting of cement and reduce its suitability for the manufacture of wood-cement composites. Wood-wool was pre-treated by soaking it in cold water for 1, 2 and 3 d or soaking it in hot water for 1, 2 and 3 h. Pre-treated and untreated wood-wool were used to manufacture wood-wool cement boards. Portland cement was used as a binder (175% of the weight of wood-wool) and 2% CaCl_2 was used as a cement setting accelerator. The extractive content of teak decreased from 2.75% to 1.34% after soaking in cold water for 3 d. Hot water extraction for 1,2 and 3 h was not as effective as prolonged cold water extraction in removing extractives from teak and after 3 h hot water extraction the extractive content of teak was 1.5%. Hot water extraction was more effective at increasing the compatibility of wood-wool with cement and increasing its suitability for the manufacture of wood-wool cement boards. For example, after 3 d soaking in cold water the hydration temperature of wood-cement mixtures increased by 4.5% whereas after 3 h soaking in hot water it increased by 9.0%. Similarly the bending strength of wood-wool cement boards increased by 10.66 kg cm~(-2) after 3 d soaking in cold water whereas it increased by 17.58 kg cm~(-2) after 3 h soaking in hot water. Cold and hot water extraction had similar effects on reduction of thickness due to compression of 3 kg cm~(-2). Irrespective of the differences in the properties of boards made from wood-wool subjected to the different pre-treatments, all boards made from pre-treated wood-wool met the F DIN 110 standard requirements for wood-wool cement board. It can therefore be concluded that aqueous extraction of wood-wool is a highly effective method of increasing the suitability of teak for the manufacture of wood-wool cement board.