material and construction course for architecture students

department of construction technology and management building materials and construction course for architecture students

1. Woldia University Institute of Technology School of Civil and Water Resource Engineering Department of Construction Technology and Management ( CoTM ) Building Materials and Construction II course for Architecture students Chapter one Wood/Timber , steel, glass

2. Timber

3. Introduction One of the first materials used by man in the construction of shelter was wood. Obviously , the issue of sustainability is a concern and all efforts to put an end to deforestation are worth supporting. But it seems that wood will always have a place in architecture. 3

4. Growth of Wood As trees grow, they absorb carbon dioxide from the air and minerals from the soil. On examining the cross-section of the trunk of an exogenous tree we perceive several parts that are briefly described below. Pith - It the innermost central part is called pith Heart wood - This position is surrounded by the pith. It is strong & dark in colour Sap wood - this layer is present next to the heart wood. It represents growth with saps. Cambium layer - This layer is present between sap wood & inner bark. Modularly rays - these are thin radial fibers extending from pith to cambium layer. 4

5. Cont.. Inner bark – It is the inner skin of tree which protects cambium layer. Outer bark – The outer skin or cover of the tree is known as outer bark. 5

6. Properties of wood Wood is fibrous material in which the fibers run longitudinally through the wood section . Wood is viscoelastic. Wood is anisotropic. Wood is hygroscopic. It will absorb moisture and will maintain a moisture content equal to that of the surrounding air. 6

7. Classification of timber Trees growing in Ethiopia can be broadly classified into two main groups: Flowering and Non flowering. Flowering Flowering trees may be divided in to: Exogenous - out ward growing trees which make the bulk of the commercially available material for building purpose. Endogenous – inward growing trees. Such as palms and bamboos which have so far little use in engineering 7

8. Cont.. The exogenous trees are divided in to: Conifers – ever green Deciduous- hard wood . Deciduous trees are mostly the source of timber for engineering construction. Timber available from exogenous trees is divided into two main classes : Hardwoods - are close- grained, dark colored, strong, and heavy, durable and have no distinct annular rings . Hardwoods are capable of resisting all stress equally well . Soft wood- are characterized by their straight and regularly arranged Fibers, more uniform texture and light color. Soft woods are strong in tension but weak in shear 8

9. Advantages and dis advantages of timber construction Advantages of Timber construction Can be easily worked, required shape can be obtained. Timber can be easily connected using nails, screws, dowels, bolts and connectors. Suitable for attractive interior decorations. It is strong and durable, if well protected Timber is light in weight and easy to handle in manufacture, transport and construction. Economical (when locally available) 9

10. Cont.. Disadvantages of Timber construction Costly if not locally available Subjected to fire risks Not suitable for dump or wet places. Is liable to crack, wrap and decay if not properly seasoned or not treated with preservatives Needs regular care and maintenance 10

11. Seasoning of Timber The process of removing or drying moisture from freshly converted timber is known seasoning of timber. Methods of seasoning Two methods of drying are generally used 1. Natural (Air) seasoning 2 . A rtificial seasoning or Clink drying 11

12. Natural seasoning Timber is stacked in the shade (under a roof) for several weeks or months in such a way that there is a fresh air all around each piece. Here , For a successful seasoning the freshly converted timber should not be exposed to direct sunrays or severe wind. No skilled supervision is needed Cheap & simple method of seasoning. Very slow 12

13. Artificial seasoning Can be completed in 4 to 5 days Boiling : timber is immersed in water and then water is boiled for 3 to 4 hours and dried slowly. The process of seasoning is fast, but costly Kiln Seasoning : fully saturated air with a temperature 35°C to 38°C is forced in the kiln The heat gradually reaches inside timber. 13

14. Cont.. Chemical Seasoning : the timber is immersed in a solution of suitable salt and dried in a kiln. Ensures uniform seasoning of outer and inner parts of timber. Electrical Seasoning : high frequency alternate electric current is passed through timber. Resistance to electric current is low when moisture content in timber is high. 14

15. Objects / purposes of seasoning To reduce shrinkage & warping To increase the strength of the timber To increase the durability & workable properties of the timber To reduce its tendency to split & decay of the timber To make suitable for painting To reduce weight of the timber 15

16. Preservation of Timber Timber used for construction purposes should be preserved and protected from: Bacterial and fungal attack Termites and insects such as pole-borers, worms Fire Proper seasoning, natural or artificial, is most effective means of preservation. 16

17. Cont.. The resistance to decay and preservation of seasoned timber is further improved by: Impregnation with preservative chemicals Brush treatment with paint or varnish Damp proofing when appropriate Providing free circulation of air. 17

18. Strength properties of timber Generally , strength property varies widely among species even between trees in a particular species. Among the factors that seriously affect strength, moisture content takes the prominent place. Variation in strength also occur b/n different parts of a tree: with temp, size and shape of specimen, amount of defects. Strength of timber varies according to the type of loading, direction of loading as it is isotropic material. 18

19. Defects in timber Natural defects – These defects may be in the form of knots, twisted fibers , ring shakes, rupture etc Defects due to conversion–These defects are formed due to improper seasoning are radial shakes, case hardening, twisted, bowing, honey combing etc Defects formed due to insects – In this defect wood is attacked by termites, insects, beetles, stem borers etc Defects formed due to fungal action – In this defect wood is infected by fungal attack which reduces the strength of wood. 19

20. Common Ethiopian timber Local name Botanical Latin or trade name Characteristics Baharzaf Eucalyptus Broad leaf tree Lower resistance to termite Difficult to treate Kararo Aningeriaadolfifridericia low resistance to termite easy to treat Kosso Hageniaabyssinica Broad leaf tree High resistance to termite Turns to dark – red when seasoned Tid Juniperusprocera African pencil cadar Almost immune to termite Difficult to treat Shrinkage little 20

21. Cont.. Local name Botanical Latin or trade name Characteristics Tukurinchet Pygeumafricanum iron wood Red ivory Broad leaf tree Very hard or iron wood Turns to pinkish brown on seasoning Wanza Cordial African Iam east African Cordia Broad leaf tree Coarse grained Zegba Podocarpus Gracilior east African yellow wood Conifer easy to treat yellow in color 21

22. Tests Specific gravity Compresive strength Tensile strength Moisture contenet Volumetric shirinkage 22

23. Steel 23

24. Introduction Metals over 45 metals of industrial importance are found within the earth's crust Four operations are required for the production of most metals: Mining the ore Preparing the ore Extracting the metal from the ore Refining the metal 24

25. Classification of metals Metals can be classified into two major groups : A ferrous metal is one in which the principal element is iron, as in cast iron, wrought iron, and steel Nonferrous metal. is one in which the principal element is not iron, as in copper, tin, lead, nickel, aluminum , and refractory metals 25

26. STEEL Steel is the world's most important engineering and construction material It can be recycled over and over again without loss of property Properties of steel HARDNESS is the material’s ability to withstand friction and abrasion TOUGHNESS is the ability to absorb energy without fracturing or rupturing YEILD strength is a measurement of the force required to start the deformation of the material (i.e. bending or warping). 26

27. Cont.. TENSILE strength is a measurement of the force required to break the material . ELONGATION (or Ductility) is the “Degree” to which the material can be stretched or compressed before it breaks CORROSION is the irreversible deterioration and destruction of the steel material. The most common protective coating against corrosion for iron and steel is paint PLASTICITY is the deformation of a material undergoing non-reversible changes of shape in response to applied forces. MALLEABILITY describes the property of a metal's ability to be distorted below compression 27

28. Uses of steel It posses great durability. Most recycled material which can be recycled very easily . Steel can be designed into various forms Is highly used in the automobile industry Used for packaging and protecting goods from water, air and light exposure. Is used to make large sheets . Steels are used for producing industrial goodies like farm vehicles and machines . Steel is used for construction 28

29. Tests done on STEEL REBAR Tensile test Compression test Bending test Brinell hardness test Impact test 29

30. Structure of steel Steels are all alloys of iron with carbon contents between 0.05 and 2 %, with additions of manganese, chromium and other ingredient. Carbon content goes above 2.0 percent , the material becomes increasingly hard and brittle Low carbon steels, with less than 0.15% carbon, are soft and used for wire and thin sheet. Mild steels , with 0.15 to 0.25 % carbon, are the most widely used Are strong, ductile and suitable for rolling and welding 30

31. Cont.. Medium carbon steels, with up to 0.5 % carbon, are specialist steels used in engineering. High carbon steels, High carbon steels with up to 1.5 % carbon , have high wear resistance, suitable for casting Structural Steel In most cases the maximum percent of carbon is less than 0.27 31

32. Impurities in steel The principal impurities in steel are silicon, phosphorus, sulfur , and manganese. The amount of silicon in structural steel is less than 1 percent . This small amount of silicon increases both the ultimate strength and the elastic limit of steel low-grade structural steel, the amount of phosphorus is about 0.1 percent and decreasing to 0.05 percent for high-grade structural steel. Tool steel is approximately 0.02 percent phosphorus 32

33. Glass 33

34. Glass Glass is an inorganic solid material that is usually transparent It is made by cooling molten ingredients such as silica sand with sufficient rapidity to prevent the formation of visible crystals. 34

35. Types of glass based on material Soda-lime glass : This is also known as soda-glass or soft glass. It is mainly a mixture of sodium silicate and calcium silicate. Properties: It is available in clean and clear state. It is cheap. It is easily fusible at comparatively low temperature. Uses : It is used in the manufacture of glass tubes and laboratory apparatus, plate glass, window glass, etc. 35

36. Cont.. Potash-lime glass: Also known as bohemian-glass or hard glass . It is mainly a mixture of potassium silicate and calcium silicate. Properties: It fuses at high temperature. It is not easily affected by solvents . It does not melt so easily. 36

37. Cont.. Potash-lead glass: Also known as flint glass . It is a mixture of potassium silicate and lead silicate. Properties: Fuses very easily. Easily attacked by aqueous solution. Posses great refractive power Turns black and opaque. 37

38. Cont.. Common glass: Also known as bottle glass. Manufacture of sodium silicate, calcium silicate and iron silicate. Properties: Fuses with difficulty. It is brown, grey or yellow in colour. Easily attacked by acids. Uses: it is mainly used for medicine bottles. 38

39. Types of glass based on their making process Annealed Glass The molten glass is allowed to cool slowly in a controlled way until it reaches room temperature , Annealed glass is used as a base product to form more advanced glass types. Heat Strengthened Glass is semi tempered or semi toughened glass . The heat strengthening process involves heating annealed glass back up to about 650 to 700 degrees Celsius and then cooling it quickly, although not as fast as with toughened glass The heat strengthening process increases the mechanical and thermal strength of annealed glass, making it twice as tough as annealed glass. 39

40. Cont.. This glass is not often used in balustrades or similar structural applications because of its limited strength compared to tempered or toughened glass Tempered or Toughened Glass This is the most common type of glass used in balustrades or similar structural applications The cooling process is accelerated by a uniform and simultaneous blast of air on both surfaces . This process makes the glass four to five times stronger and safer than annealed or untreated glass. 40

41. Cont.. Laminated Glass Any one of the above types of glass can be laminated. The most commonly used finished product is two sheets of toughened glass, laminated together with a 1.52mm thick Polyiynil Butyral (PVB) interlayer . Offers many advantages. Safety and security are the best known of these 41

42. Glass is used for Packaging Tableware Housing and buildings Interior design and furniture Appliances and Electronics Medical technology, optical glass Radiation protection from X-Rays Fibre optic cables Renewable energy 42

43. Glass Cladding Is suitable to most applications, both internal and external. Is often used as an architectural feature in restaurants, shops, office reception areas Is ideal for wet areas, such as kitchens, bathrooms, laundry rooms and swimming pools. Is that it maintains its appearance for a long time. 43

44. Thank you! 44