Quality Assessment of Air-dried Teakwood Boards Using Moisture Content Gradients

ABSTRACT The determination of moisture content gradients is one of the most important steps for assessing the quality of wood drying. The general aim of this work was to study the quality of air-dried teakwood boards according to the gradients of moisture content in thickness and length. Six representative boards (40 × 180 × 2,300 mm) were sampled from a stack air-dried under shelter, divided into 30 equal parts in length and measured with a resistance moisture meter, resulting in four treatments: two depths (1/4 and 1/2 thickness) and two surfaces (inner and outer) of measurement. As main results, we can conclude that the air-drying quality can be considered good, mainly for two reasons: i) the average moisture content gradients in thickness were comparable to those reported in literature for kiln-drying of less thick boards; ii) the range of average moisture content among boards (2.5 p.p.) was satisfactory for a drying process carried out without environment control. Length moisture content gradient was completely different from that reported in literature, in which no board tops had smaller moisture content than the parts comprehended in between the tops.

摘要：含水率梯度（moisture content gradients）的测定是评估木材干燥质量的关键环节之一。本研究的核心目标为基于厚度与长度方向的含水率梯度，评估气干柚木板材（air-dried teakwood boards）的干燥质量。
本研究从棚下气干的堆垛板材中抽取6块代表性试样（规格为40×180×2300 mm），沿长度方向将每块板材均分为30段，采用电阻式含水率测定仪（resistance moisture meter）开展测试，共设置四种测试方案：两种测试深度（板厚的1/4与1/2处）以及两种测试面（内层与外层）。
主要研究结果表明，本次气干（air-drying）工艺的干燥质量可评定为优良，主要依据如下两点：其一，厚度方向的平均含水率梯度与现有文献中较薄板材窑干（kiln-drying）的相关研究结果相当；其二，各试样间的平均含水率极差为2.5个百分点（p.p.），对于无环境控制的干燥工艺而言，该指标表现令人满意。
但长度方向的含水率梯度则与现有文献报道存在显著差异：本研究中未出现板材端部含水率低于两端端部之间区段的情况。