Timber as a construction material: Preservation methods|Fire resistance treatment|Tests on Timber
Preservation methods of timber:
Timber is one of the most use construction material, because it posses
great characteristics and cheap in price as compare to other materials. But
it gets defect easily, so preservation of it is require.
Chemical technique with which we get increase durability,strength and less
vulnerable to attack by white ant and other microbe is known as preservation
of Timber.
It can sort in seven different class.
Ascu treatment:
Ascu is powdery form preserver, which is made up of Hydrated Arsenic
pentoxide (1 part),Blue Vitrol or Copper sulphate(3 parts),Potassium di chromate(4 parts).
6 part of Ascu powder and 100 part of water is mix together to make
solution. This solution is sprayed on the timber.
This treatment protect timber against white ant.
Chemical salt:
In this method solution is made up of water,natural salt,Copper sulphate,
Mercury Chloride, Sodium Fluoride and Zinc Chloride is applied on timber.
This solution penetrates deep inside a timber, which result in instant
increase in weight of timber.
Coal tar
Coal-tar:
This method is also known as tarring method, because in this hot coal-tar
is applied in timber with brush.
This method is suitable for rough use timber work like door,window and it's
frame. It is also very good for part embedded inside ground.
Creosote oil method:
Creosote oil is produce by distillation of tar. Creosote is sprayed on
timber at high pressure and temperature till 2 hour. This spraying
process is known as creosoting.
This process increase a resistance against fungus attack, so life of timber
is increase. This method is good option for railway sleeper,pile and poles.
It should not adopted on interior of building.
Charring method:
Poled are inlay in ground, so it's lower end is vulnerable to insect and
fungus attack. In this case its lower end is extinguish into water after
charred with water. This preservation process is known as charring
method.
Oil paint
Oil paint method:
Oil paint is most commonly use and most easy preservation method for the
timber. In it two to three coat of oil paint is applied on the surface of
the timber. This surface resist the penetration of water inside a timber
body and make it durable.
Solignum method:
It is toxic liquid. In this method, this hot liquid is applied on the
timber with brush. As this liquid is toxic in nature, it protect timber
from attack of white ant.
Fire resistant treatment for timber.
One of the major disadvantage of timber is poor fire resistant property
as compare to other major building material. Specially non-refractory
wood. Now question come in your mind, what is non-refractory
wood.
According to fire catching property wood can be divided into two
way
Refractory wood:
which hardly vulnerable be catch fire easily.
Eg:sal and teak wood
Non-refractory wood:
obviously which can catch fire easily.
Eg:chir,deodar,fir(because it contain more oil)
Now, lets come on over point about fire resistant treatment. There are
two method for it.
By use of chemicals:
In this treatment chemical call borax or sodium arsenate use. This
chemical is apply on timber, which increase the fire resistant of timber
and it burn slowly.
This chemicals are known as "Fire Protection
Compounds" or "Anti pyrines".
Sir Abel's process:
This is a most uses process for fire resistant. It adopted in three
phase
In first phase, dilutes sodium silicate's coat is apply
In second stage, slaked fat lime is applied.
In third and last stage concentrate sodium silicate is applied.
Different tests on Timber:
There are vareity of timber. Opt out of it is headache. To over come it,
there are different kind of test on timber, which decide different
characteristics of timber. So out of it we can decide best suitable one
for us.
Specific gravity:
Specific gravity of timber should be 1.54. To decide it test should be
conducted on 50mm×50mm×150mm timber plank. It's volume,weight and moisture
content should be measured.after putting values in following equation, we
will get specific gravity of timber.
G= ( W×V)
×(100/(100+M))
Where,
G= specific gravity
W =weight
V= volume
M= moisture content
Volumetric shrinkage:
Shrinkage of timber should be least, to make sure it this test is
conducted.
Timber's initial volume and weight is measured. Then it is heated in oven
around 1030°C tempreture until it reach at constant weight.
Then to decide volumetric shrinkage and moisture content percentage, values put in following equations.
Volumetric shrinkage=(Vi - Vf) / Vi
And
Moisture content =(Wi - Wf) / Wi
Where,
Vi= initial volume
Vf= final volume
Wi= initial weight
Wf= final weight
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Bending test:
If timber is used as a beam of a structure, then it will face extreme
tension at center of it, to make sure bending capacity of beam this test is
conducted.
To conduct this test 50mm×50mm×100mm timber section consist fiber parallel
along it's length is use.
Three point load is applied at two third length of beam at 3mm per minute
till the appearance of crack in it. It is calculate based on simple bending
equation.
Bending strength of timber should be 40 to 100 Mpa.
Tension test:
In timber beam tension derive at lower section of beam. To determine
suitability of timber as beam tension test is conducted.
Test specimen of 10mm×10mm is fitted in UTM (universal testing machine).
Tension applied at 2.5mm per minute until occurrence failure.
Tension test is calculated by ratio of maximum tension and cross section of
test specimen.
Minimum tension of timber should be 80 to 190 Mpa.
Compression test:
Timber column is loaded under compression. To determine it's capacity,
compression test is adopted.
In it sample logged of size
50mm×50mm×200mm sized is fitted in UTM( universal testing machine). Timber
grain must be perpendicular to compression. Initially 2.5KN compression is
applied. Deformation at center length gauge is measured. According to it
compression is measured.
Compression of column should be 30 to 80 Mpa at 15% moisture content.
Note:
From all observation we show that moisture content greatly affect on
performance of timber. Following are some require moisture content for
different purpose.
Timber use in structure of building should have moisture content 10% to
20%
Flooring timber should have 7% to 12% moisture content.
Timber of building frame contain 13% to 20% moisture.
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Timber as construction material-types, structure of wood, defect of
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