|The following is for those who want to know more about Robinia hardwood with special attributes.
Have fun reading and we will gladly assist you with additional info : firstname.lastname@example.org
See also info from Institute of Technology (Wood in ground contact) Knowledge About Wood
See here data sheet on standard warehouse of robinia wood fra SkovTrup.
As spring news offers SkovTrup robinia seeds for planting - fun to have a tree that has produced the materials used for your patio, raised beds, pergola, etc.. - standing in your own garden!!
Left image shows a Hungarian Robinia plantation in operation - Right image shows a sawn squid stick.
|The following is from the Technological Institute's website.
Physical and mechanical properties of Robinia hardwood & other types of wood:
Physical and mechanical properties are the moisture content of 12%, unless otherwise indicated.
Density at 12% moisture content -> 580-704-760-862-900 kg/m3
Density, 0% moisture content -> 540-668-720-819-870 kg/m3
Flexural strength -> 103-134-169 MPa
Modulus of elasticity (sagging) -> 10.100-14.100-17.800 MPa
Compressive strength in fiber direction -> 62-72-81 MPa
Shear Strength -> 11-12,8-17,1 MPa
Hardness, [Brinell] End wood -> 6,7-7,8-8,8 MPa
Hardness, [Brinell] Tree -> 2,8-3,4-4,7 MPa
Comparison between the following species:
Density kg/m3 at 12% moisture / / Hardness (Brinell) Tree kp/mm2 / / Compressive strength
along the fiber direction MPa / / Bending Strength
MPa / / Elasticity GPa
Robinia hardwood - Robinia pseudoacasia L.
Density kg/m3 at 12% moisture -> 580-760 - 900
Hardness (Brinell) Tree 3.4 kp/mm2
Compression strength along fibretning -> 62-81 MPa
Flexural Strength -> 103-169 MPa
Elasticity -> 10.1 to 17.8 GPa
Beech - Fagus sylvatica L.
Density 12% moisture -> 690-710-750 kg/m3
Hardness (Brinell) Tree 2.8 kp/mm2
Compression strength along fibretning -> 52-56 MPa
Flexural Strength -> 105-118 MPa
Elasticity -> 10-16 GPa
EG - Quercus robur L.
Densitet kg/m3 ved 12% fugt -> 670-710-760
Hårdhed (Brinell) Sidetræ kp/mm2 3,4
Trykstyrke langs fibretning MPa -> 53-65
Bøjestyrke MPa -> 90-100
Elasticitet GPa -> 10-13
Scotch Pine - Pinus sylvestris L.
Density 12% moisture -> 500-520-540 kg/m3
Hardness (Brinell) Tree 1.6 kp/mm2
Compression strength along fibretning -> 45-47 MPa
Flexural Strength -> 83-89-100 MPa
Elasticity -> 10-12 GPa
|Wood in soil - Understanding Wood 5/2004
One must think, when timber is used in ground contact. Not all wood species can be used unprotected. Some must be impregnated to hold, while others can do without additional wood for over 20 years. The choice depends on the requirements for the durability, the structure, effect and the ability to maintain the wood. In this edition of Understanding Wood looks at the wood's natural durability in ground contact, and how it can be protected.
|In recent years there have been considerable attention to impregnation and chemical preservatives. A growing environmental awareness has meant that the requirements for proofing on the environment and health have been strengthened. Recently with the introduction of Biocidal Products Directive.
As a result of the strong focus on environmental impacts of impregnating agents are many alternatives to treated wood appeared. Often one sees explained that thuja, larch and Douglas had to be as durable as impregnated wood - or to a surface treatment is sufficient to give the tree the desired resistance.
But there are so many factors influencing the durability of wood when it has contact with the ground, we too often find that these reservations are not enough to achieve a satisfactory result.
|Figure 1. Guiding lifetimes for the wooden parts used in ground contact. Factors such as wood quality, size and local soil conditions play a crucial role in sustainability. Priming Oil is good, but unfortunately not enough to protect wood in ground contact.
Ground contact and durability. By the term ground contact is meant that the wood is in contact with ground or fresh water, and thus have a permanent moisture content of more than 20%. This makes the tree susceptible to attack by wood-degrading fungi. By contact is also believed those parts of the structure that is above ground such as fence posts that can be attacked by such drilling beetles. It is in the range between ground and air that have a high wood moisture, and a significant air exchange. Therefore, it is often in this zone that is optimal conditions for the wood-degrading fungi.
In Danish, two concepts of natural durability of wood: 'duration', which merely refers to the time and 'durability', as well as duration is also used for mechanical strength. In the following, used the term durability, which is also used in the standards cited in the fact box on page 4.
Wood duration of ground contact
Use of wood is often driven by the power of example. Means that we - wisely - use the tree on the way we've seen the success of others. As for the wood resistance to decay, it often happens after simple proven rules of thumb. This means in some cases, we do not exploit the tree's durability to the fullest. With a more detailed knowledge of the wood and construction types, providing a good durability under the desired conditions, we can use the tree for several purposes without making mistakes.
We have a reasonable knowledge of the lifetimes of untreated heartwood in soil (DS / EN 350-2). Shatter-tree lifespan in soil is usually less than 2 years. Pressure impregnated sapwood, achieves a more durable than the heartwood. It is widely known that oak has a high natural durability. Less known is that the robinia actually have an even better durability than oak, see figure 1.
The figure shows the recommended service life of wooden parts used in ground contact. Factors such as wood quality, cross-sectional dimensions, construction design and local conditions will affect the current lifetime. Therefore it is also a very large spread in the lifetime of the individual tree species. The figure applies only to untreated heartwood.
Sapwood of all tree species are classified as 'not sustainable'. The lifetimes has based on long-term English studies The biological kind Durability of timber in ground contact, GA: Smith & RJ Rosten, 1996, BRE, DS / EN 350-2 and experience matter.
"Self-impregnating" tree species
Some users do not want to use impregnated wood. As an alternative to this product, you see recommended the so-called self-impregnating wood species, which covers the species Thuja, larch and Douglas fir. The term is believed that these species has ingredients that reduce the biological degradation. This concept can be misleading, as there has not been any tree species that are self-impregnating.
The term derives primarily from older sources and based on experiments with wood that is grown under conditions other than the wood that we can buy today. Recent evidence of the durability of these species are not available.
|Left image shows untreated larch-poles - after 4 years in ground contact it is strongly degraded. Picture middle impregnated poles in pine. Splintering wood has achieved a greater durability than heartwood. Picture to the right - long-term study of wood in the soil, which includes the new pressure impregnating agents tested.
It has been common to use larch in ground contact, for example, fence posts, sand boxes and play stands. But this tree species does not perform well in ground contact, if you expect a durability of more than 5 years cf. Figure 1
If it is also a construction in which there may be injuries at break, should the use of other tree species such as oak,robinia or other overseas timber species with proven durability.
Tests and experience show that the heartwood of larch has approximately the same durability as the heartwood of pine. The difference between the two species is that a pine trunk contains only about 50% heartwood, where a larch trunk contains approx. 80%. Obviously this is a better natural durability of larch topics, but this does not make it into a self-impregnating wood species.
Some places are used a surface treatment on the part of the wood to be in the ground. This coating may be priming products or tar-containing products.
Unfortunately, this has no great impact, because most of the biocidal products that are commercially degraded by soil contact. Moreover, there are currently no surface treatment products approved for use in ground contact. Boron-containing products disappear from the tree with water (diffuse out) and the copper-containing products will no longer penetrate into the wood than a few millimeters. Since it is often in cracks increase the biological decomposition starts, these coating products do not have any effect.
Furthermore, it should be noted that the biological activity in soil can vary greatly from location to location - even from meter to meter. So you risk that the wood in some places keeps significantly shorter time than expected.
Pressure Impregnated wood is not the same today as 20 years ago. Pressure proofing agents arsenic and chromium have been prohibited for use on impregnation plants in Denmark and it is no longer allowed to use organostannic funds for vacuum impregnation. Denmark has generally been the frontrunner to put environmental awareness and efficiency in focus on wood area. We have therefore developed in Denmark means that are more environmentally sound to use. But we must not prevent the importation of impregnated wood from other countries where less environmentally friendly materials are used.
When pressure-treated wood should be used in ground contact, use only wood that is labeled either according to current standards such as the Nordic NTR rules or the European standard EN 351st.
Wood used in ground contact must be impregnated to NTR impregnation class A. This corresponds to the penetration class P8 in EN 351-1 Risk Class 4 (ground contact). In this way it is ensured that the amount of biocides are matched to the application. Do not use wood impregnated with other classes. It's only wood species pine and spruce, which is approved for pressure impregnation of NTR in Class A.
According to EN 350-2 are both larch douglas fir and hard Impregnate. This means that the pressure impregnation fluid is difficult to penetrate into the sapwood. Larch douglas fir, and all have a very small splinter part, why pressure impregnation does not penetrate very far into the wood.
Today there are only few products that are approved for the impregnation of Class A, and all contain copper, triazoles and boron. One should also note that pressure treated wood according NTR well be cut or shortened if it gets finished.
However, there are P.T. no products on the market that are EPA approved for use in ground contact. It is therefore not recommended to cut or shorten the parts to be in contact with soil.
By using impregnated posts in ground contact one must be aware that sapwood achieves a more durable than the heartwood. This means that a breakdown of the wood will occur inside the stem and, therefore, will not always be to detect visually.
Security and lifetime assessment
Generally, you should think carefully about when wood is used in ground contact, and you should carefully consider the safety in relation to the structure used. There may be injuries at break, you should periodically review the tree's condition.
Basically, you should choose a tree species with a high density (hardwoods), large dimensions and ingredients from wood-degrading fungi.
The best solution is to avoid burying the wood in the ground, but instead to use such pole-shoes or similar constructive approach.
When choosing wood for constructions, it must be considered and take into account:
Natural durability of wood species
Sapwood has no durability of in soil
The use and of nature influences
Possibility of injury by an unexpected breaking
Possibility of constructive wood protection, eg. pole-shoes
Thick dimensions lasts longer and better than thin
desired operating time
The key standards
Use of common, well-designed standards, provide professional wood-user an opportunity to survey the extensive knowledge about these things. Also gives standards a common European measurement scale for durability, impact on the tree, etc. This makes it easier to assess and describe the various wood products and their application across national borders.
DS / EN 335 Wood and wood-based materials durability - Definition of hazard classes of biological degradation.
DS / EN 350 Durability of wood and wood based products - Natural durability of solid wood.
DS / EN 351 Sampling of treated wood
DS / EN 460 Wood and wood products durability - Natural durability of solid wood. Guide to durability requirements for wood in relation to risk classes.
DS / EN 599 Biological testing of preservatives
ENV 807 Wood preservatives. Determination of the preventive efficacy against soft rot fungi, and microorganisms in soil
DS / EN 927-1 Wood preservatives and coating systems for exterior wood
NTR Document 1 Nordic wood preservation classes
NTR Document 2 Nordic rules for approval of funds for industrial wood preservation
NTR Document 3 Nordic rules for quality control and labeling of treated wood.
For more information contact
Telephone: +45 72 20 23 14
|Source - Frederikshavn Council's website
There are alternatives to impregnated wood!
Many people use impregnated wood when, for example to build carports, tool sheds and play equipment. But it is not necessary. Wood which is not impregnated, is often just as well. Tree species such as oak, teak, thuja and western red cedar has a good natural durability - even in contact with soil. If this you are building does not have ground contact, there is usually no need to use impregnated wood, here it may well be replaced with, for example. spruce, pine or larch.
Impregnation is a chemical treatment which increases the lifetime of the wood material. Impregnated wood, may contain a number of environmental contaminants such as chromium, copper, arsenic, tin, borates and creosote. Today, it is forbidden to sell and use wood that is impregnated with creosote and arsenic. Both creosote and arsenic is believed to be carcinogens, and arsenic can also cause acute and chronic poisoning. Chromium and creosote may not be produced in Denmark, but may still be imported and sold.
Use impregnated wood properly.
If you can not avoid using impregnated wood, you should look for the label. There must be NRT on the end of the timber. The Timber's own control system, which should guarantee that it does not include banned substances. Approval does not mean that the means used are harmless, but health and environmental risks are found acceptable. The use of impregnated wood does in any case a higher environmental impact than if we choose unimpregnated wood with a good natural durability.
Impregnated wood should only be used for such posts to be buried in soil and other vulnerable places in the building. And it's actually not as durable as we think. A pillar of impregnated wood in soil can only hold for 20 years, according to Timber Information. A stud in Robinia wood in soil lasts for 35-40 years - without impregnation. Common pine which have no ground contact can last 100 years! There is thus no reason to build a carport of impregnated wood.
In addition, EPA discourages the use of impregnated wood in playgrounds and play equipment. And remember that it is prohibited from burning impregnated wood itself.
Impregnated wood is environmentally hazardous waste and must be returned to recycle. Currently, it deposited impregnated wood, while working to develop new technologies for the treatment of wood, so the environmental impact will be less of destruction.
Use the wood's natural durability.
Wood has a natural durability, and various tree species can be with different lifetimes withstanding the effects of both land, water and air.
It is important to select heartwood - ie. the portion of the wood that comes from the innermost portion of the stem. It is much more durable than the sapwood, which originates from the outer part of the tree.
Expected durability of heartwood from selected tree species in contact with soil
Less than 5 years of life: Ash - Beech - Birch - El - Poppel.
5 to 10 years of life: Elm - spruce - Scots pine - Douglas.
10 to 15 years of life: Larch - Thuja - Cypres.
15 to 25 years of life: Oak - Western Red Cedar - Robinia (36 years)
Constructive wood preservation:
Constructive wood preservation means that to protect the structure against climate impacts and to use the various tree species correctly. Try to follow the following guidelines:
Try to avoid, the tree makes contact with soil and water. Carports, playhouses, tool shed, etc. can be built without soil contact by placing the bars on a pile shoes made ​​of steel or a concrete footing with embedded anchor. Be in this regard the additional stiffening of the structure.
Facades and fences kept free of soil and vegetation.
Keep the wood dry, protect it from rain and channel the water away - eg. with eaves or roof.
Protect end caps and upturned faces with cover planks, beveled cuts or face sealing with wood.
Ensure tight joints between the constructs, so dirt and water can not penetrate.
Ensure proper ventilation of the woodwork.
What to choose?
There is no doubt that the impregnated wood including is popular because it is a cheap and effective solution. The more environmentally friendly tree species with a good natural durability currently cost a little more, and there is currently a limited supply of them.
They are also slightly more difficult because they require more maintenance and frequent inspection of the structures. But in return we save ourselves and the environment for a range of harmful substances which are difficult to dispose of.
For more information on the topic by Green Guide Hanne Lauritsen
at telephone 96225441 or email: email@example.com
Source: "Handbook on impregnated wood and alternatives" of the Environmental Protection Agency and Timber Information.