This standard outlines the procedures for assessing the inherent durability of timber and the effectiveness of wood preservative treatments against marine borer infestations. It is applicable to commercially used timber species in marine environments, providing guidance on evaluating timber resistance and preservative performance under tropical seawater conditions.
Overview
This standard outlines the procedures for assessing the inherent durability of timber and the effectiveness of wood preservative treatments against marine borer infestations. It is applicable to commercially used timber species in marine environments, providing guidance on evaluating timber resistance and preservative performance under tropical seawater conditions.
Audience
Contents
Structure
This section defines the focus of the standard on the methodology for exposing timber blocks treated with preservatives in marine conditions. It details the arrangement of test specimens on rafts, including positioning treated and untreated blocks at specified intervals and depths below the low water mark to ensure uniform marine exposure.
Describes the selection of heartwood from commercial timber species suitable for marine exposure, specifying minimum tree sampling requirements and guidelines for obtaining specimens from multiple growth regions when variability exists. Details the number and preparation of treated and untreated specimens per tree, including preservative types and absorption levels.
Specifies specimen block size and quantity per tree species, describing the types of preservatives used, their absorption levels, and the number of replicates required to achieve statistical validity. Also outlines the overall test setup including specimen numbers and sets.
Explains the positioning of treated and untreated specimens on rafts suspended vertically at fixed intervals and immersion depths. Describes raft construction, capacity, and layout for consistent exposure, as well as adherence to statistical design principles for reliable test outcomes.
Addresses selection criteria for test locations based on marine fauna diversity and borer attack intensity. Recommends deploying tests at multiple sites to capture variable environmental conditions, ensuring comprehensive evaluation of timber durability.
Outlines procedures for counting borer holes on all specimen surfaces, estimating affected surface areas, calculating percentage damage, and criteria for specimen rejection based on damage extent. Includes optional correlation with mechanical strength data when available.
Details testing protocols for two types of preservatives at specified absorption levels applied to selected non-durable timber species. Describes the preparation of treated and untreated specimens, statistical analysis of results, and reference to related preservation standards.
Provides guidance on the experimental design, inclusion of standard control species, and application of statistical methods such as variance analysis and significance testing to interpret durability and preservative efficacy data. Emphasizes consistent rounding of numerical data as per relevant standards.
Specifies the types of preservatives and their treatment levels used in testing, referencing established codes of practice for timber preservation. Outlines specimen preparation requirements and the use of replicates to ensure statistical relevance.
Lists associated standards applicable for rounding off numerical values, timber preservation practices, and laboratory testing methods. Highlights the importance of international coordination and data contributions from forestry research institutions.
Frequently Asked
The standard recommends using at least two non-durable timber species for preservative efficacy evaluation: a hardwood species such as Mangifera indica (Mango) and a softwood species like Pinus roxburghii (Chir pine). Additionally, standard species—one hardwood and one softwood—treated with defined preservatives are used as control benchmarks to maintain consistency across different test durations.
Specimens must be derived from the heartwood of commercial timber species suitable for seawater exposure. For each species, samples should come from at least two trees, including multiple growth regions if applicable. Each tree should yield one untreated specimen and four treated ones (two preservatives at two absorption levels each). Specimens are typically sized at 30 cm length by 5 cm width and thickness, with three replicate sets per absorption level to support statistical reliability.
Timber specimens are exposed by suspending them vertically on specially designed rectangular rafts in marine tidal or subtidal zones, ensuring natural exposure to marine borers. Specimens are tied at 5 cm intervals starting 0.35 meters below the low water mark, allowing marine organisms to attack untreated and treated wood under realistic environmental conditions.
The standard assesses two main preservative types: oil-based (creosote or creosote-fuel oil mixture at 1:1 ratio) and water-soluble (copper-chrome-arsenic composition). Each preservative is applied at two absorption levels—160 and 320 kg/m³ for creosote, and 16 and 32 kg/m³ (dry salt basis) for CCA—to test their efficacy against marine borer damage.
Damage assessment involves counting the number of borer holes on six surfaces of each specimen (four longitudinal and two end surfaces), estimating the approximate area affected on each, and calculating the total percentage of surface area compromised by borer activity. Specimens with 50% or more surface area affected are considered unacceptable. When available, mechanical strength data may be recorded to correlate physical degradation with borer damage.
The standard advises employing an appropriate experimental design based on the number of species tested, incorporating control species for temporal comparisons. Statistical analyses such as mean calculation, standard deviation, coefficient of variation, ANOVA, and regression may be used to evaluate differences between treated and untreated specimens and to correlate damage with strength loss, ensuring robust and interpretable results.
To account for variability in marine borer fauna and attack intensity, the standard recommends conducting tests at multiple sites with diverse biological communities. Selecting numerous test locations enhances representativeness and reliability of durability assessments by encompassing a range of environmental conditions and borer species.
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