Friday, November 9, 2012


                                       CARPENTRY AND JOINERY
     The timber which is to be used for the structural purposes is to be dressed, planed.  Framed and placed in proper position. The term carpentry includes can  forms of  construction which have to resist stresses due to loads coming upon them. Thus a carpenter constructs permanent timber works such as roofs, floors, etc as well as  temporary timber works such as  scaffolding, shoring, centering , etc.
     The term joinery is used  to indicate the art of preparing I internal fittings and finishing’s of timber. Thus a joiner constructs timber works such as doors, windows,  stairs, floor boards, furniture, cupboards, etc. Thus the joinery is used for delicate c instruction requiring precise workmanship  for enhancing the architectural beauty of timber.
     In India , the  word carpentry is used only to incite both types of trades, namely, carpentry an joinery and the workman who is employed for the work of  carpentry and  joinery is known as a carpenter.
    In this chapter, the salient features of carpentry and joinery   will discussed.

                                          TECHNICAL TERMS IN CARPENTRY
                               The  cement concrete possesses the following important properties :
1)      It had a high compressive strength.
2)       It is free from corrosion and there is no appreciable effect of atmospheric agents on it.
3)      It  hardens with age and the process of hardening continues for a long  time after the concrete had attained sufficient strength. It  is this property of cement concrete which gives it a distinct place among  the building materials.
4)      It is proved to be more economical than steel. This  is due to the fact that sand and pebbles or crushed rock, forming the bulk of cement concrete, to the extent of about 8% to 90%, are usually available at moderate cost.  The form work, which is of steel or timber , can be sued over and over again or for other purposes after it is removed.
5)      It binds rapidly with steel and as it is weak in  tension, the  steel reinforcement  is placed in cement concrete at suitable places to take up the tensile stresses.  This is teemed as the Reinforced Cement Concrete or simply  R.C.C.
6)      Under the following two conditions,  it had a tendency to shrink :
a)      There is initial shrinkage of cement concrete which is mainly due to loss of water through forms, absorption by surfaces of forms, etc.
b)       The shrinkage of cement concrete occurs as it hardens. This tendency of cement concrete can be minimized by proper curing of concrete.
c)        It had a tendency to be porous. This is due to the presence of voids which are formed during and after its placing. Following two precautions are necessary to avoid this tendency. :
There should be proper grading and consolidating of the aggregates. The minimum water-cement ration should be adopted.
7)      It forms a hard surface, capable of resisting abrasion.
8)       It  should be remembered that apart form other materials, the concert e comes to the site in the form of raw materials only. It  final strength and quality to the site in the form of raw materials only. It final strength  it. However the depend entirely  and local conditions and persons handling it. However the materials of which concrete is composed may be subjected to rigid specifications )
     Following materials are required for making the R.C.C. work :
1)      Cement
2)      Aggregates
3)       Steel
4)       Water.
1)      Cement : Before the introduction of ordinary Portland cement, the lime was used as a cementing materials. Most of the cement concrete work in building construction is done with ordinary Portland cement at present. But other special varieties of cement is done with ordinary Portland cement a present. But other special varieties of cement  Such as rapid hardening cement and high alumina cement are used under certain circumstance. The cement should comply with all the standard requirements.
2)       Aggregates : These are the inert or chemically inactive materials which form the bulk of cement concrete. These  aggregates are  bound together by means of cement. The aggregates are classified  together by means of cement The aggregates are classified into two categories : Fine and coarse :
      The material which is passing though BIS test sieve no. 480 is teemed as a fine aggregate. Usually, the natural river sand is used as a fine aggregate. But at places. Where natural sand is not available economically , the finely crushed stone may be used as a fine aggregate. 
The material which is retained on BIS test sieve no. 480 is termed as a coarse aggregate, The broken stone is generally used as a coarse aggregate, The nature of work  decides the maximum size of the coarse aggregate,  For thin slabs ad walls, the maximum size of coarse aggregate should be limited to one-third the thickness of the concrete section, 
      The aggregates to be used for the cement concrete work should be  hard, durable and clean. The aggregates should be completely free from lumps of clay, organic and vegetable matter, fine dust, etc. The presence of all such debris prevents adhesion of aggregates and hence reduces the strength of concrete.
3)      Steel : The steel reinforcement is generally in the form of round bars of mild steel. The diameters of bars vary from 5 mm to 40 mm. Sometimes the square bass such other constructions, the reinforcement may also consist of sheets of rolled steel of suitable thickness. The hyrax which is a steel lath may also be sued  used as  the steel reinforcement.
4)      Water : This is the least expensive but most important ingredient of concrete.  Impunities such as oils, alkali, acid etching  general the water which s fit for drinking should be sued of remaking, concrete.
It may be noted that sometimes the ingredients other than  above are added in concrete to give it certain improved qualities or for changing different physical properties admixture. The addition of an admixture may  improve the concrete with respect to its strength hardness, workability, water resisting power, etc. Following are the commonly used admixtures.
     Alum.  Aluminium  sulphate, barium oxide,  bitumen, calcium chloride, coat ash, common  salt, iron oxide, lime, mineral oils, organic oils, potassium chloride, silicate  cement ration falls done and can even be brought down up to the limit of 0.25, Thus it gives quick setting concrete, However the use of calcium chloride is not suitable for concrete with reinforcing bars.
 It is necessary to know the complete detail of any admixture before its recommendation  concrete with reinforcing bars.
 It is necessary to know the complete detail of any admixture before the recommendation together with the following  factors :
                                           I.            Grading curves of aggregates and their respective properties,
                                         II.            Method of construction, quantity of cement  per m3 of concrete
                                       III.            Requirement f slump ad retention,
                                       IV.             Temperature variation,
                                         V.             Type and make of cement, and
                                       VI.             Water-cement ratio,
    Depending pun their respective activities in  the concrete mix, the admixtures and be classified in the following five categories.
1         Accelerators,
2          Air  entraining admixtures,
3          High range of water reduces or super plasticizers,
4          Normal range of water reducers of plasticizers, and 
5          Retarders.
It may be noted that some admixture may have the combined effect of the above individual activities. The popularity of various types of admixtures in concrete is increasing rapidly because of the following advantages available from their use.
 1, adjusting the final setting times of concrete,
  2 Higher early and ultimate strengths,  
   3, higher slump and self-levelling concrete,
    4 ,  increasing durability of concrete,
   5, lesser water-cement ratios,
   6, lesser water-cement ratios,
6         , reduction quantity of cement,
7          Reducing quantity of cement,
8          Reduction in the  permeability of concrete,
9         Lesser water-cement ratios,
10      Reducing quantity of cement,
11      Reduction in the permeability of concrete ,
12      Time savings in terms of repair and  maintenance, etc, ,,,,,,,

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