Effect of moisture and active ingredient concentration on CCA-C retention

The strategy of wood preservative treatment companies is to control the factors that influence retention, such as the concentration of the preservative solution and wood moisture, to reach values higher and closer to the standard minimum. The objective of this study was to reduce the consumption of Chromated Copper Arsenate type C (CCA-C) without affecting the quality of the treatment by determining the most efficient wood moisture interval for two genotypes of Eucalyptus sp. at different concentrations of active ingredients. A total of 54 fence posts of the species E. cloeziana and the hybrid E. camaldulensis x E. urophylla were treated. The pieces were randomly selected from three drying piles with different storage times in the yard (long, intermediate, and short). The active ingredient concentrations tested were 1.2, 1.4, and 1.6%. Retention analysis was performed to evaluate the quality of the preservative treatment. For both analyzed materials, the lowest and highest average retention values were observed in short and long storage piles and concentrations of 1.2% and 1.6% A.I. CCA-C, respectively. For E. cloeziana, only posts with a long storage time and treated with 1.6% of CCA-C were considered suitable for use in contact with the soil, according to the Brazilian standard, while for the clonal hybrid, posts with intermediate and long storage times, treated with 1.6% of CCA-C were considered suitable for use in contact with the soil. It was observed that CCA-C retention in the studied fence posts was directly influenced by the concentration of active ingredient in the preservative solution and by the storage time of the materials in the yard.