1. BASICS OF CIVIL ENGINEERING

2. CIVIL ENGINEERING MATERIALS
TIMBER
IRON
STEEL

3. TIMBER Oldest form of materials used in construction
Also used for other needs of human beings
Timber is obtained from trees

4. World timber is derived from the English world timbrian which means to build
Timber means wood that is good for building or carpentary which is having a circumference of 600mm
Converted timber means timber which is sawn into suitable commercial sizes
Rough timber means timber obtained after felling a tree
Standing timber means timber contained in a living tree

5. CHARACTERISTICS OF GOOD TIMBER
Uniform colour
A Freshly Cut Surface should give a sweet smell
Regular annual rings
Straight and close fibers
Heavy in weight.
Durable
Possesses the property of elasticity
Fire resistant
Hard
Should be strong for working as a structural member

6. Uses of timber
Used in the form of piles, posts, beams, lintels, door window frames
Used for flooring, ceiling, paneling, and construction of partition walls
Used for formwork of concrete, centering for arch work, scaffolding, transmission pole and fencing
Wagon and coach building, marine installations and bridges

7. The power of tree It precipitates rainfall and lowers temperature
It prevents depletion of ozone layer
It prevents soil erosion
It purifies the air by producing oxygen . It is estimated that a hectare of tree will produce about 10 tonnes of oxygen per day which is sufficient for 45 persons to live for one year

8. Classification of tree

9. Trees are classified as above
Exogenous trees grow outwards and increase in bulk by forming concentric rings from the Centre. Outside rings are called annual rings as it grows per year
Exogenous trees are again classified into conifers and deciduous
Conifers are evergreen trees the leaves of which do not fall till a new ones are grown
They produce cone shaped fruits they are called conifers
They show distinct annual rings

10. Deciduous trees- leaves fall in autumn and new ones appear in spring season
Timber for engineering derive these type of trees
These trees yield hard wood
They do not show distinct annual rings example ,teak, jackwood, rosewood etc
Endogenous trees grows inward and fibrous mass is seen in their longitudinal section
Very limited engineering use example bamboo,cane,palm

11. Cross- section of Exogenous tree

12. Parts of a tree
Pith- innermost central portion of the tree is called pith. It contains cellular tissues and nourishes the plant in its younger age and when the plant becomes aged it dies
Heart wood –inner angular rings surrounding the pith constitutes the heart wood , usually dark in colour, it indicates dead portion of the tree and does not take part any role in the growth of tree
Sap wood –outer annual rings surrounding the pith constitutes the sap wood , it is light in colour and weight, it indicates recent growth , it takes active part in the growth of tree

13. 4. Cambium layer-thin layer of sap between sap wood and inner bark are known as cambium layer. It indicates sap which are not converted into sap wood 5. Inner bark –inner layer covering the cambium layer is known as inner bark 6. Outer bark-outer cover of the tree is known as outer bark 7. Medullary layer- thin radial fibers extending from the pith to cambium layer is known as medullary rays

14. Processing of Timber Felling of tree Seasoning of timber
Conversion of timber
Preservation of Timber

15. Seasoning of timber
When a tree is cut , it contains about 50 % more of its weight as water . removal of this water is known as seasoning
The timber is to be dried for attaining this
Seasoned timber should be kept away from moisture content and from humidity

16. Objectives of seasoning
To allow the timber to burn if used as a fuel
To decrease the weight
To impart hardness ,stiffness, strength and better electrical resistance
To increase the resistance power of timber
To maintain shape and size
To make it easily workable and to facilitate operations during conversion
To make it fit for receiving treatment
To make it safe against attack of fungi
To make it easy for gluing
To reduce the tendency of timber to crack, shrink and warp

17. Methods of Seasoning of timber Natural seasoning Artificial seasoning

18. Natural seasoning(air)
Timber is cut into planks or scantling
They are stacked horizontally or vertically
The ground for stack is to be leveled
Brick support is constructed and over which it is to be kept
The timber logs are arranged in layers on above the other as shown in figure. The timber of equal size should be kept in each stack

19. Each layer should be separated by spacers
Each layer should be separated by spacers . Size of spacers should be 35mm*25mm to 50mm*35mm
The distance between the spacers depends on the size of the wood
The length of stack depends on the length of timber pieces
Stack to be protected from fast flowing wind, rain , extreme heat or sun . So it should be covered

20. Natural seasoning

22. advantages
The moisture content of wood can be brought down to about 10 to 20%.
It does not require skilled supervision
For thicker sections, artifical seasoning is uneconomical where natural seasoning can be adopted.
Cheap and simple

23. disadvantages Less control over air
The drying of different surfaces will not be even or uniform
Chance of attack by fungi and insects during seasoning.

24. Artificial seasoning
To make the drying more uniform and even, by controlled conditions, artificial seasoning is adopted
It reduces the time for seasoning shrinkage, cracking and warping are minimized in artificial seasoning.
The wood with desired moisture content may be obtained by this.

25. The various methods used are, Boiling Chemical Seasoning
Artificial seasoning
The various methods used are,
Boiling
Chemical Seasoning
Electrical seasoning
Kiln seasoning
Water seasoning

26. 1. Boiling Immersed in water and then boiled for about 3 to 4 hours
Dried very slowly under a shed
The periods of seasoning and shrinkage are reduced
In place of boiling steam is also used but expensive

27. 2. Chemical seasoning(salt)
Immersed in solution of suitable salt
Taken out and seasoned in the ordinary way
The interior surface dries in advance the chances of formation of external cracks reduced

28. 3.Electrical seasoning High frequency AC current is used
The resistance increases as the wood becomes more and more dry
This is the most rapid method of seasoning
Initial maintenance cost is very high

29. 4. Kiln seasoning In this seasoning is carried out in a chamber
Timber is arranged inside the chamber with space for circulation of air
Air which is fully saturated with moisture at 350 C to 380C admitted in to the chamber by some arrangement
The forced air is allowed to circulate round the timber as air is fully saturated with moisture the evaporation from the surface is prevented and the heat gradually reaches inside the timber pieces
The relative humidity is gradually reduced
The temperature is then raised and maintained till the desired degree of moisture content is reached

30. Kiln seasoning

31. Water seasoning Timber is cut into small pieces
They are immersed in water , preferably in running water
Thicker end is pointing upstream
Timber is taken out after 2 to 4 weeks and allowed to become dry

32. advantages Handling and transportation cost of wood can be reduced
Improve the Engineering properties of wood
Dimensional stability of finished products can be maintained
Eases the workability of timber
Before the application of paints, varnishes, preservatives ,glues etc. seasoning of wood is a prerequistite.

33. Sl no
item
Natural seasoning
Artficial seasoning 1
Moisture content
Dificult to reduce below 15 to 18%
Can be reduced to any level 2
Nature
Simple and economical
Expensive and technical 3
Quality of timber
More liable to attack by insects and fungi
Kiln seasoned timber are less liable for attacks 4
space
Requires more space for stacking
Less space 5
Speed
slow
quick 6
strength
Stronger
weaker

34. Timber defects Defects due to conversion Defects due to fungi
Defects due to insects
Defects due to natural forces
Defects due to seasoning

35. Defects in timber Defects due to conversion
While converting in to commercial forms the following defects may occur
Chip mark- marking due to chips on the finished surface
Diagonal grain-due to improper sawing of timber, diagonal mark on the straight grain
Torn grain-This defect is caused when small depression is formed on the finished surface of the timber by falling a tool
wane – original rounded surface on the manufactured piece of timber

36. 2)Defects due to fungi
Fungi are minute microscopic plant they attack only when certain conditions are satisfied
Moisture content of the timber above 20%
There is presence of warmth and air for the growth of fungi
Rot – physically weak
Blue stain , brown rot, Dry rot, heart rot .
Sap stain ,wet rot ,white rot

37. 3. Defects due to insects
Beetles – insects having beating mouth, Due to this timber is converted into fine flour like powder.
Marine borers- insects that bore the wood, found in salt water, timber loses colour and strength due to this.
Termites- these are also white ants, live in colonies and eat way the timber in different ways.

38. 4)defects due to natural forces
Abnormal Growth
Rupture of Tissues
Most important is knot and shake

39. Defects due to natural forces
Knots , shakes and rind gall(abnormal swelling)
Classification of knots(branches which are broken or cutoff from tree)
Dead knot- connected with surrounding wood- not safe to use for engineering purposes
decayed knot – due to fungi
Live knot-sound knot- difficult to remove - ,makes sawing difficult, can be used for Engineering purposes
Loose knot-preliminary stage of dead knot

40. Round knot-shape is round
Tight knot-preliminary stage of live knot
2.Twisted fibers- happens due to twisting of young trees by fast blowing wind.
Fibres are twisted in one direction , not suitable for engineering purposes.
3.Shakes –cracks which are partly or completely separate the fibers of wood
cup shakes
heart shakes
Ring shakes
Star shakes
Radial shakes

41. 4.Water stain- wood is sometimes discoloured when it comes into contact with water, found in converted timber 5.Wind cracks- if wood is exposed into atmospheric agencies -its exterior surface shrinks, results into cracks. 6. Rind galls- these develop at places from where branches are improperly cut. -Swelling due to abnormal growth is the reason for this -Timber at this part is very weak.

42. Knot and rind gall

44. Shakes

48. Radial shake and twisted fibres

49. Cup shake and heart shake

50. Shakes

51. defects due to seasoning
1)bow- curvature formed in the direction of length
2)case hardening-exposed surface dries up speedily and the inside will be under tension
3)check-crack which separates fibers of wood
4)collapse-uneven shrinkage the wood sometimes flattens during drying.
5) cup- curvature is formed in the transverse direction
6)Honey combing-due to stresses developed during drying various radial and circular cracks develop in the interior portion of the timber

54. Preservation of Timber
Objective
 To increase the life
 To make it durable
 To protect the timber from attack of destroying agents such as fungi and insects

55. Types of preservatives
1) Ascu treatment
2) Chemical salts
3) Coal tar
4) Creosote oil
5) Oil paints
6) Solignum paints

56. Ascu treatment
1) Developed in forest research institute Dehradun and consist of the following
Parts by weight of Arsenic pentoxide
Parts by weight of copper sulphate
The material available in powder form
Six parts by weight of Ascu mixed in 100 parts by weight of water and applied in the wooden surface

57. 2)Chemical salts
Water borne preservatives mostly salts dissolved in water
Commonly used are copper sulphate, Mercuric chloride ,Sodium fluoride and Zinc chloride

58. Coal tar
When coal tar is applied on the surface of wood it is called tarring
Unpleasant smell and appearance
Adopted only for unimportant work
Fire resistant

59. Creosote oil Obtained by distillation of tar Process is as follows
1. Timber is thoroughly seasoned and dried
2. It is then p laced in an air tight chamber
3. Air is pumped out fro the chamber
4. Creosote oil is pumped in to the chamber
5. After a period of about 1 or 2 hours when timber is completely absorbed the oil it is to be taken out

60. Oil paints Timber surface is coated with 2 or 3 coats of oil paints
Oil paint preserve timber from moisture and make it durable

61. Solignum paints
These paints preserve timber from white ants as they are toxic in nature
Mixed with colour pigments and applied with the help of a brush

62. Method of preservation
1)Brushing- applying preservative by using brush
2)Charring-kept wet for an half an hour and then burning
3)Dipping and Steeping(Let sit in a liquid to extract a flavor or to cleanse)
4) hot and cold open tank treatment
5) injecting under pressure
6) spraying

63. Factors affecting strength of timber
Abnormalities of growth
Faults in seasoning
Invasion of insects
Irregularities of grain
Moisture content
Presence of knot, shakes etc
Way in which the timber piece is cut from the log

64. Decay of timber-causes
Alternate wet and dry condition
Bad storage and stacking of timber
Attack of fungi
Improper seasoning
Insects beetles ,marine borers, termites
Keeping in contact with damp wall, damp earth etc

65. Use of timber without taking out sap wood from the structure
use of seasoned timber without using preservative
Use of unseasoned wood with the application of protective of paint or tar