Compatibility of four eastern canadian woods with gypsum and gypsum-cement binders by isothermal calorimetry

Abstract

In order to determine the feasibility of manufacturing wood-gypsum and wood-gypsum-cement particleboards, the hydration reactions of four Eastern Canadian wood species with gypsum and Portland cement were studied. The compatibility of hot water extracted and raw wood particles with both gypsum and a gypsum-Portland cement mixture were determined for jack pine, balsam fir, aspen and white birch by isothermal calorimetry. The four species were found to be compatible and suitable for the manufacturing of inorganic-bonded wood composite boards on the basis of the compatibility factor. The hot water extractive content was low in the four species and did not have a consistent impact on the compatibility factor. Nevertheless, hot water soluble extractives did have an impact on the time required to reach the maximum heat flux, delaying it to undesirable levels particularly in the case of balsam fir mixed with neat gypsum. However, the effect of balsam fir on neat gypsum hydration was markedly reduced by the addition of 30% Portland cement. Hot water extraction of the wood particles and the addition of Portland cement to the wood-gypsum mixture significantly reduced the time required to reach the maximum heat flux. The gypsum-cement mixture was less sensitive to the inhibitory effect of wood than neat gypsum.