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BUILDING MATERIALS

                                               Building Materials are the most important part of buildings. `BUILDING MATERIALS' as it's name itself signifies that the materials used to construct a building is known as Building Materials. or we can say that any materials which is used for construction purpose is called Building Materials. These materials include too many things such as rocks, bricks, wood, cement, sand, chips etc.

ROCKS :-    A rock is a naturally occurring  solid substance that is normally made of minerals. Stones are also derived from rocks which form the earth crust and have no definite shape & size but are mixture of two or more minerals. The rocks from which stones are obtained are classified into three groups.:-

1) Geological Classification :- Geologically, the rocks are classified into three types as follows:-

• Igneous rocks :- Igneous rocks are formed due to the solidification of molten masses laying below or above the earth surface. It has a crystalline glossy or fused texture.

• Sedimentary rocks :-  Sedimentary rocks are formed due to the gradual decomposition of minerals like sand, clay etc. generally by setting water. These are also called stratified because these rocks are formed in layers. Limestone & Sandstone belong to this category of rocks.               

 

• Metamorphic rocks :- Metamorphic rocks are formed due to the alteration of original structure under heat and excessive pressure. Marble is an example of metamorphic rocks.                            

2) Physical Classification :- Physically, the rocks are classified as follows :-

• Stratified rocks :- Stratified rocks are those which exhibit distinct layers which can be separated. The Limestone, sandstone & slates are the example of stratified rocks.                              
        
• Unstratified  rocks :- Unstratified rocks are those which do not show any sign of strata and cannot be easily split in to slabs. The granite & marble are the examples of unstratified rocks.        
        

3) Chemical Classification :- Chemically, the rocks are classified as follows :-

• Silicious rocks :- The silicious  rocks are those which contain silica as the main constituent . The granite, quartzite, gneiss are the example of silicious rocks.                                                         
     
• Argillaceous rocks :- The argillaceous  rocks are those which contain clay & alumina as the main constituent . The slate, laterite, kaoline are the example of argillaceous  rocks.                     
   
• Calcarious rocks :- The Calcarious rocks are those which contain lime & calcium carbonate as the main constituent . The limestone & marble are the example of Calcarious rocks.                        
   

Important Building Stones

• Granite :- It is an igneous rock . It is mainly composed of quartz, *felspar and mica. Its specific gravity is 2.64 & compressive strength varies from 70 to 130 MN/m sq . Its colour depends upon that of felspar which may be brown, grey, green and pink. A fine grained granite offers high resistance to weathering. It can be easily polished and worked. It is used for exterior facing of buildings.
• NOTE:- Felspar is a silicate of aluminium with varying amount of potash, soda or lime. 

• Slate :- It is an argillaceous rock. It is mainly composed of alumina mixed with sand or carbonate of lime. Its specific gravity is 2.8 and compressive strength varies from 60 to 70 MN/m sq. It has gray or dark blue colour. A good slate is hard, tough and fine grained. It is suitable for use in cisterns. The slates in the form of tiles us used as an excellent roof covering materials.                                                                                                      

• Gneiss :- It is an silicious rock. It is mainly composed of quartz and felspar. It is more easily worked than granite. It is a good material for street paving.

• Sandstone :- It is a sedimentry rock of silicious variety. It is mainly composed of quartz, lime & silica. Its specific gravity is 2.65 to 2.95 and compressive strength varies from 35 to 40 MN/m sq. Its usual colour are white, gray,brown, pink etc. The fine grained  stones are strong and durable. It is suitable for ashlar work, mouldings, carvings etc.

• Limestone :- It is a sedimentry rock of calcarious variety.  Its specific gravity is 2.6. It is available in brown, yellow & dark grey colour. It is used in large quantities in blast furnaces. It may be used as stone masonry for walls.

• Marble :- It is a metamorphic rock of calcarious variety.  Its specific gravity is 2.7 & is available  many colours. It is very hard and takes a fine polish. It is used for carving and decoration works.

• Kankar :- It is an impure limestone containing 30% of alumina & silica. The hard kankar is used for foundation of buildings.

• Laterite :- It is sandy claystone containing high percentage of iron oxide. It has a process and cellular structure. Its specific gravity, varies from 2 to 2.2. The laterite block are suitable as building stones whereas nodular laterite proves a very good road metal.

• Moorum :- It is a decomposed laterite and has deep brown or red colour. It is used in surfacing fancy paths and garden walks.

• Quartzite :- It is a silicious sandstone which has been subjected to metamorphic action. It is strong & durable. It is used as a road metal or railway ballast or in concrete. 

BRICKS

                                                     The brick is the most commonly used buildings material and used for constructing walls , column, roof, paving floors etc. A good brick clay contains 20-30 % of alumina, 50-60 % of silica and the remaining constituents are lime, magnesia, sodium, potassium, manganese and iron oxide. It may be noted that :-

• The excess of alumina in clay makes the brick crack and wrap on drying.
• The excess of silica in clay makes the brick brittle and weak.
• The excess of lime in clay cause the bricks to melt and distort during burning.
• The alkaline salt present in the bricks, absorb moisture from air which on drying leaves powder deposit on the brick. This effect is known as efflorescence. It is also caused if the clay used for making brick contain pyrite and the water used for pugging the clay contain gypsum.

MANUFACTURING OF BRICKS

                                                               The manufacturing of bricks contains four major operations:-

i)  Preparation of brick clay :- First of all , the earth is dug out in clear weather and cleaned of stones, pebbles, grits, vegetable matters etc. The earth after digging out is left to atmospheric action for few weeks. This process is known is weathering. It is found that 1.5 to 2.5 cum of earth is required for moulding 1000 bricks. The clay is then tempered in pug-mills.

      NOTE:- The process of mixing clay, water and other ingredients to make bricks is known as kneading.

  ii)   Moulding bricks :- After preparing the clay, the moulding of bricks is carried out either by hand or by machine. In hand moulding, the bricks are moulded by hand i.e manually. It is preferred where manpower is cheap and readily available. The hand moulding may be done either on ground or on table accordingly these are termed as ground moulding or table moulding.

                                           The bricks are moulded in machine when large number of bricks are to be manufactured in a short time. The machine moulding may be performed either by plastic method or dry process method.

                                     

      NOTE:- The hand made bricks are superior to machine made bricks for facing purpose.

iii) Drying of  bricks :- After the bricks are moulded, they are dried. The drying of bricks may be natural or artificial. In natural drying , the moulded bricks are kept in the sun for a day or two so that they become sufficiently hard to be handled safely. These bricks are now arranged in rows on their edges on a slightly raised ground called hacks. A little space for the free circulation of air is kept for each bricks. The air and sun dried bricks are adequately strong and durable. If the bricks are not properly dried before they are burnt, they may get cracked and distorted during the burning process.

                                      The artificial drying is used when bricks are required on a large scale and at a rapid rate.

iv) Burning of  bricks :- The burning of dry bricks is done either in a clamp or in a kiln. In India, both clamp and kiln burning are practised. It may be noted that the average out-turn of first class bricks in clamp burning is about 60% whereas for kiln burning it is about 80 to 90%. 

NOTE:-      1}  The burning of bricks in kilns is complete within 24 hours.

                   2}  The bricks should be burnt at temperature from 1000`C to 1200`C.

                   3}  The bricks after burning in kilns require about 12 days to cool down for unloading.

CLASSIFICATION OF BRICKS

The bricks are classified as under :-

• First class  bricks :- These bricks are well burnt having smooth and even surface with perfect rectangular shape and uniform reddish colour. These bricks should not absorb water more than 20% of its own dry weight after 24 hours immersion in water. It should have a minimum crushing strength of 10.5 MN/m sq.
  

•  Second class  bricks :- These bricks are slightly over burnt having rough surface and not perfectly rectangular in shape. These bricks should not absorb water more than 22% of its own dry weight after 24 hours immersion in water. 
  
• Third class  bricks :- These bricks are not properly burnt (under burnt) in the kiln and hence these are soft and can be easily broken.These bricks should not absorb water more than 25% of its own dry weight after 24 hours immersion in water.
  
• Jhama  bricks :- These bricks are over burnt with irregular shape. These bricks are dark bluish in colour.
  

NOTE:-      1}  The standard size of bricks are 19 cm x 9 cm x 4 cm or 19 cm x 9 cm x 9 cm

                   2}  The specific gravity of bricks is about 2.

                   3}  The number of bricks required for one cubic metre of brick masonry are 550.

SPECIAL BRICKS

                        The special bricks differ from commonly used building bricks with respect to their shape, specification and special purpose for which they are made. Following are some of the special bricks:-

• Squint  bricks :- These bricks are used in construction of acute and obtuse squint quoins.
  
• Paving bricks :- These bricks are extensively used for street pavements, stable floors, garden walls etc.
  
•  Round bricks :- These bricks are used for circular pillars.
  
• Perforated and Hollow bricks :- These bricks are used for partition walls or panel walls in multi-storeyed buildings.
  
• Refractory bricks :- A good refractory bricks should have the capability of withstanding high temperature and low coefficient of expansion and contraction. Following are the three types of refractory bricks:-

             (a) Acid bricks {Fire bricks and silica bricks}

          (b) Basic bricks {Magnesite bricks, dolomite bricks and bauxite bricks}

           (c) Neutral bricks {Chrome bricks, chrome-magnesite bricks and spinel bricks}

BUILDING TILES

                The building tiles are thin slab of brick clay, burnt in kiln. The various types of tiles are flooring tiles, roofing tiles (i.e. pot tiles,*pan tiles and flat tiles), wall tiles, drain tiles and glazed earthenware tiles.

                                    LIME

                                     The lime is calcium oxide (CaO) obtained by calcination of limestone(white chalk), kankar and other calcarious substances. It is not found in nature in the free state.

                                        It is used as a matrix for concrete, for plastering walls, ceiling etc, for improving soil for agriculture purposes and in the production of glass. It is also used as a flux in the manufacture of steel, and in the manufacture of paints.

Types of lime:-

• Quick lime :-  It is the lime obtained after the calcination of  pure limestone. It is amorphous and highly caustic having no affinity for carbonic acid.
  
• Slaked lime or hydrated lime :-  It is the lime formed by the absorption of water by qucik lime. The process of chemical combination of quick lime with required quantity of water is known as slaking.
  
• Fat or rich lime :-  It is the lime which has high calcium oxide (about 95%) content and can set and become hard only in the presence of carbon dioxide from atmosphere. This type of lime is perfectly white in colour. It has high plasticity. It slakes rapidly with considerable evolution of heat