Treatability of refractory species with amine and amine/ammoniacal formulations of ACQ

This work was designed to quantify differences in preservative penetration of western U.S./Canadian species when treating with amine copper quat type D (ACQ-D) and a hybrid amine/ammoniacal copper quat formulation (ACQ-D), at both ambient and heated temperatures. These results were compared to that obtained with chromated copper arsenate (CCA). Kiln-dried western white spruce (nominal 2 by 4), air-dried Douglas-fir (nominal 2 by 4), selected for maximum heartwood, and air-dried western hemlock and Pacific silver fir (95 by 95 mm) were cut into end-matched sub-samples. End-matched replicates of each species were treated with CCA, ACQ-D, and ACQ-D at ambient temperature, and ACQ-D and ACQ-D at 60?C. Core borings were removed for penetration and retention analysis from the center of the heartwood face between incisions. Both ACQ formulations allowed for improved penetration and retention of treated wood beyond that obtainable with conventional CCA treatments, either through the addition of ammonia, the use of heat, or both. The heated ACQ formulations and ACQ-D at ambient proved to be more effective than ambient temperature CCA at penetrating all four species. The heated ACQ-D formulation gave the best results, with both Pacific silver fir and western hemlock meeting the American Wood Preservers’ Association standard for ground contact. White spruce and Douglas-fir treated with ACQ-D met the penetration requirement of the Canadian Standards Association decking standard (CSA 080.32). It should be noted that, in commercial practice, compliance with these standards should be better than that observed here as sapwood faces would be included in the proportion present in the charge, whereas this work was done entirely on heartwood faces.

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