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Industrial Crops and Products 34 (2011) 1146–1149

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Industrial Crops and Products

jo ur nal homep age: www.elsevier.com/locate/indcrop Wood–wool cement board using mixture of eucalypt and poplarAlireza Ashori a, ∗ , Taghi Tabarsa b , Khadijeh Azizi c , Reza Mirzabeygi ba Department of Chemical Technologies, Iranian Research Organization for Science and Technology (IROST), Tehran, Iranb Department of Wood and Paper Technology, Gorgan University of Agricultural Sciences & Natural Resources (GUASNR), Gorgan, Iran

c Department of Wood and Paper Science and Technology, Islamic Azad University, Karaj Branch, Karaj, Iran

a r t i c l e i n f o

a b s t r a c t

Article history:Received 21 February 2011Received in revised form 28 March 2011Accepted 29 March 2011

Available online 13 May 2011Keywords: Wood–wool Cement EucalyptBuilding material

Bending strength

This study was carried out to explore the possibility of making cement-bonded wood–wool composite building products using eucalypt (Eucalyptus camaldulensis) and poplar (Populus deltoides). The experi- mental design consisted of three treatments – ratio of wood–wool mixture, percentage concentration of cement, and calcium chloride (CaCl 2 ). The mechanical properties in terms of modulus of rupture (MOR), modulus of elasticity (MOE) and internal bond (IB) strength were investigated. The ratios of wood–wool to cement were 40:60 and 60:40 by weight. The addition of the woody material to cement clearly reduced the maximum hydration temperature and increased the time to maximum temperature. Eucalypt was generally less compatible with cement than poplar wood. Test results showed that boards made with poplar wood–wools had superior properties compared to the eucalypt and mixed wood–wools. The pres- ence of eucalypt in mixture of woody materials typically resulted in decrease in mechanical properties. It has been noted that a dose of 5% of CaCl2 by weight of cement can enhance the effect of cement. Application of Duncan’s Multiple Range Test for the mean values of the results showed that the effects of all variables and their interactions on the mechanical properties in terms of MOR, MOE and IB were highly significant (p ≤ 0.01%). The mechanical properties of most produced boards were found to satisfy the minimum requirements of ISO standard.

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1. IntroductionWood–cement composites have been used in the fabrication of construction materials for more than 60 years. They have the poten- tial to provide a wide range of products for building applications by using different forms of wood-based materials. The develop- ment and application of wood–cement composites attest to their attraction as building materials ( Okino et al., 2004).Wood–wool cement board (WWCB) is a new generation of wood–cement composites, made from wood–wool (ribbonlike par- ticle called “excelsior”), Portland cement and small amounts of additives. Wood–wool is the reinforcing agent, cement is the binder, and additives are the catalyst. These ribbons are coated with cement and pressed into panels that have densities in the

range of300–500 kg m−3 . The wood–wool/cement ratios vary from 0.4 to

0.6 by weight. WWCBs were developed primarily as substitutes for asbestos–cement, and have been promoted mostly in the last 25 years. Wood–wool is attractive for use as noncombustible sound- absorbing ceiling, thermal insulations and wall panels ( Wolfe and Gjinolli, 1996). ∗ Corresponding author. Tel.: +98 228 2276629; fax: +98 228 2276629.

E-mail address: ashori@irost.org (A. Ashori).

The use of wood particles to cement has accelerated rapidly over the past decade, primarily because of improvements in process technology and economic factors. Further development of these applications of bio-renewable materials for use by the cement industry could provide attractive new value-added markets for forest products or agricultural residuals, while simultaneously replacing the asbestos-based cement products. The primary advan- tages of using lignocellulosic materials as reinforcement in cement are their low densities, low cost, nonabrasive natures, the possibil- ity of high filling levels, high specific properties, biodegradability, availability of wide varieties of fibers throughout the world, and the generation of an agricultural economy ( Karade, 2010; Tabarsa et al., 2011).

The wood to cement compatibility is still a problem in the development of WWCBs. It has been found that organic materials inhibit cement setting and reduce cement strength. As described by Hachmi and Moslemi (1989), wood–cement compatibility gen- erally decreases as the extractive content increases. Extractives are generally composed of terpenes, fatty acids, tannins, carbohydrates, and inorganic materials ( Ashori et al., 2011). It has been reported that the water-soluble extractives of wood retard and sometimes inhibit the normal setting and strength development properties of cement during the production of wood–cement composites. Stud- ies have shown that hemicelluloses, starch, sugar, tannins, certain

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