PINE

Physical and mechanical properties of pine

Pine tree is one of the most widespread types of trees not only in Russia, but also in the entire world. In Russia it makes up around ⅙ of total forests. The height of a pine tree ranges from 20 to 40 metres. A tree lives for 300-500 years on average. It is a fast growing type of trees. Its annual height growth under favourable conditions amounts to 0.8-1m.

Pinewood exhibits distinct growth rings in all sections; there is a core and resinous canals. The texture is even. Pinewood has a relatively low average density due to vast differences in structure of early and late wood. The density of early wood is 2-3 times lower than the density of late wood in an annual growth zone. An average content of late wood in a growth zone is 27%. An average number of growth rings in 1 cm of pinewood on the territory of Russia ranges from 4 to 14. A larger number of growth rings is representative of trees from the northern regions of the country.

Physical properties of pine

Moisture content

An average moisture content in a growing tree amounts to 112% in sapwood and 33% in heartwood. The moisture content of sapwood increases along the height of the tree, while the moisture content in the tree core remains relatively the same. Daily and seasonal fluctuations of moisture content occur. The highest moisture content (20-30% above average) is evident in the mornings, by the end of the day it decreases to a minimum (30-35% below average) and in the evenings, it starts to increase again. The moisture content of a freshly cut pine tree is 85% on average (sapwood — 100-120%, heartwood — 30-40%, bark — 120%).

Drying process

Wood is usually dried before usage. Pinewood (with 12% moisture content) on average shrinks 6.7% for early wood and 7.5% for late wood in the tangential direction. Nevertheless, if the air humidity increases, it causes moisture absorption. The processes of drying and moisture absorption can virtually be seen as mutually inverse. For this reason, in order to describe and evaluate size changes of wood under conditions of changing humidity a wood swelling factor is used (the ratio of % size changes to % moisture content).

Average value of a wood swelling factor for a regular pine:

  • radial — 0.18;
  • tangential — 0.31;
  • volumetric — 0.50.

Pinewood is less inclined to corrode during drying than broad-leaved hardwood trees. Choosing the right method of drying and the correct arrangement of wood in the drying room can substantially decrease the number of defects.

Density

Like other softwood, pinewood exhibits relatively low-density levels. An average estimate of pinewood density with 12% moisture content is 505 kg/m³, while density of absolutely dry pinewood comes to 480 kg/m³.

Permeability to gases and liquids

Pinewood possesses high levels of air and moisture permeability. With an excessive pressure of 0.1 MPa (on one side of a wood exemplar), the value of air permeability in the radial direction amounts to 56.2 mm³/cm²/s for sapwood and 2.6 mm³/cm²/s for heartwood.

For comparison, the value of air permeability of oakwood under the same pressure comes to 0.13 mm³/cm²/s. High levels of moisture permeability allow an extensive and successful usage of protective liquids and substances. Judged by the way they absorb protective liquids, pine sapwood belongs to light absorption woods, pine heartwood — to medium absorption woods, while spruce and larch belong to hard absorption woods.

Thermal properties

Heat conductivity increases with higher density. Heat expansion of pinewood is hard to detect as it often overshadows by the processes of drying and moisture absorption. With heat insulation, pinewood exhibits properties, which substantially surpass properties of such materials as aluminum (used for manufacturing windows) and are slightly superior to those of PVC.

Light permeability

Light-sensitive equipment can detect light radiation through pinewood that is up to 35mm thick. X-radiation shows virtually no effect on the structure of wood and its hardness; for that reason, it is used to detect flaws in wood assortment.

It has been established that pinewood can be effective for screening neutron radiation. Pinewood shields of 100mm can substitute polyethylene protective coating and guarantee heat resistance and durability.

Mechanical properties

Hardness

The highest hardness properties are exhibited by pinewood that is indigenous in the northern part of the European Russia. Only Caucasian fir surpasses it in this quality.

Breaking point:

  • static bending — 70-92 MPa;
  • stretching along the grain — 100-116 MPa;
  • compression along the grain — 40-49 MPa;
  • shearing along the tangential plane — 6.6-8.1 MPa;
  • elasticity coefficient during stating bending — 8.0-13.1 GPa.

Technical and functional properties

Impact elasticity — 28-51 kJ/m².

Hardness:

  • face plate — 28-33 N/mm²;
  • radial — 21-25 N/mm²;
  • tangential — 16-23 N/mm².

Pinewood belongs to softwoods — up to 40 N/mm² (hardwood — 41-80 N/mm², extremely hard wood — more than 80 N/mm²).

Due to its softness, pinewood easily yields to cutting tools.

It is excellently susceptible to polishing — the size of micro asperities amounts to 8-60 micrometres, while for ash and maple trees it is up to 200 micrometres (due to particular qualities of their structural asperities).

Pinewood is also highly resistant to biological effects such as fungal infections.

Trees are the eldest companions of humans; they have always been our source of heat and energy and a reliable and matchless building material.

Wood contains cellulose, lignin, ash-forming mineral and organic elements, variability of qualities and their combinations that along with differences in cellular structure makes different types of wood light or heavy, rigid or flexible, hard or soft. For this reason wood of different types and properties becomes an excellent and primary choice among raw materials.

One of the main characteristics of wood is a diversity of types, sizes, shapes and properties of wooden materials. It meets all possible requirements for construction and manufacturing. Wood possesses high impact elasticity, high levels of endurance, hardness, and excellent exploitation qualities, which play a significant role in building and construction. Dry wood exhibits great heat, sound and electric insulation properties. Under suitable conditions of employment, wood absorbs and disperses sound vibrations, which make it a perfect material for musical instruments.

On account of its unparalleled texture and colour, wood is also an aesthetically pleasant material, and its appearance can be further enhanced by different types of finishing. Wood is easily processed by mechanical means, it can be glued together, secured by nails, screws, bolts and other fastening elements. Defective parts of wood in constructions can be easily replaced, while the constructions themselves can be simply rebuilt. Besides, wood is resistant to oxidation, corrosion and various acidic solutions. Wood can withstand numerous strong impacts and cope with heavy loads; it easily absorbs antiseptics and fire retardants, which also increase its value. It is simple to combine wood with other materials in order to attain desired functionality or aesthetic effect.

Fireproof tree (information from Johanna Paungger and Thomas Poppe’s book)

If you have visited the village of Kramsach in Tirol at least once, with its open air museum of houses, barns, utensils and work tools that are hundreds of years old, you must have paid attention to wooden stove benches, boards, oven forks, trenchers and fireplaces. Incredibly, almost no one asks how all these semicircular oven forks, which were used to take red-hot pots, jugs and frying pans out of the stove, have become so long lasting and existed for centuries without any damage incurred. Another curious thing is the fact that the wood right in the middle of fire (in wooden stoves and fireplaces) in fact did not burn. Of course, it was completely black, but never burning or smouldering. It can be explained in this way: on certain days, the phases of the moon “take care” of fireproof trees.

A tree that was felled on March 1, especially after sunset, will be resistant to burning, regardless of the moon phase and the sign, in which it is positioned at that moment. It is a very rare but effective rule: those who have tried can confirm it. In the past, many of the home utensils, yard buildings, barns, log cabins and alpine huts were made of such wood in order to protect them from fire.

We are open to dialog and you can always count on our warm attitude. Please, visit us, we certainly have something to be proud of and what to offer to your attention.

We are waiting for you at our construction sites daily from 9 a.m. To 6 p.m.
Oktyabrskaya naberezhnaya 112, Saint-Petersburg, Russia
tel: 8 (812) 438-07-67 (additional: *1 in tone mode)
(Construction site) +7 (921) 412-76-82