Effect of wood moisture content on rate of fixation and leachability of CCA-treated red pine

Wood freshly treated with chromated copper arsenate (CCA-C) was freeze dried and re-equilibrated to low moisture contents (MC) without allowing chromium reduction (fixation) so the effect of wood MC per se on rate and quality of fixation could be evaluated at different fixation temperatures. While chromium reduction occurred at all wood MCs, including approximately ovendry conditions, the rate of chromium fixation was greatly reduced with decreasing MC below the fiber saturation point. As has been observed with wood fixed under high MC conditions, the rate of chromium reduction was accelerated greatly with increasing temperature. There was significantly higher leaching of all components, and especially arsenic, for samples fixed at all temperatures if the wood MC was lower than the fiber saturation point MC during fixation. The lower the wood MC, the slower the rate of chromium reduction and the higher the leaching of all CCA components. High temperature (90 degrees C) fixation under non-drying conditions resulted in the best leach resistance of the conditions tested.