Concrete Technology: Cement Production and Aggregates Unit 1 Part 3

Que1.12. What’s meant by  total? Compactly describe their  bracket. 

Answer  total These are inert accoutrements  which are mixed with binding  material  similar as cement or lime for manufacturing of mortar or  concrete. Aggregate are used as  padding in mortar and concrete and also  to reduce their cost.  Bracket of Aggregate  1. According to Geological Origin  Natural Aggregate  1. These  summations are generally  attained from natural deposits of beach  and gravels or from chases by cutting  jewels.  2. The cheapest among them are the natural beach and clay which have  been reduced to their present size by natural agents,  similar as water,  wind and snow,etc.  3. The swash deposits are the most common and are good quality.  ii. Artificial Aggregate  1. The most extensively used artificial  total are clean broken bricks and  air cooled fresh blast- furnace- sediment.  2. The broken bricks of good quality  give a satisfactory  total for  the mass concrete and aren’t suitable for  corroborated concrete work if  the crushing strength of  slipup is  lower than 30 to 35 MPa.  3. The bricks should be free from lime mortar and lime sulphate cataplasm.  4. The bricks  total isn’t suitable for leakproof construction.  5. It has poor resistance to wear and hence isn’t used in concrete for the  road work.  2. According to Size  Fine Aggregate  1. The  total which passes through4.75 mm sieve and retained on 75  micron sieve are known as fine  total.  ii. Coarse Aggregate  1. The  total retained on4.75 mm sieve are known as coarse   total.  iii. each-  by- Aggregate  1. It’s the combination of both coarse and fine  total.  3. According to Shape  Rounded Shape  a. The  total with rounded  patches( swash or shore clay) has   minimal voids ranging 32 to 33.  b. The only disadvantage is that interlocking between its  patches is less  and hence the development of bond is poor, making it  infelicitous for  high strength concrete and pavement.  ii. Irregular Aggregate  a. The  total having  incompletely rounded  patches(  hole beach and clay)  has advanced of voids ranging from 35 to 38.  b. It  needed  further cement paste for a given plasticity.  iii. Angular Aggregate The  total with sharp, angular and rough   patches( crushed  jewels) has a  outside of voids ranging from 38 to  40. The interlocking between the  patches is good.  iv. short Aggregate  a. An  total is  nominated  short when its least dimension( consistence) is   lower than three- fifth of its mean dimension.  b. The presence of these  patches should be  confined to 10 to 15.  4. According to Unit Weight  Normal Weight Aggregate The generally used  total, i.e.,  beach and gravels; crushed  jewels  similar as  determinedness, basalt quartz,  sandstone and limestone; and  slipup cargo,etc., which have specific   earnestness between2.5 and2.7  yield concrete with unit weight ranging  23 to 26 kN/ m3 and crushing strength at 28 days between 15 to 40 MPa  are  nominated normal weight concrete.  ii. Heavy Weight or High- viscosity Aggregate Concrete having unit  weight of about 30, 31, 35, 38, 40, 47 and 57 kN/ m3 can be produced by  using typical goethite, limonite, baryte, magnetite, hematite,  ferrophosphorus and scrap iron, independently.  iii. Light Weight Aggregate The light weight  total having unit  weight up to12 kN/ m3 are used to manufacture the structural concrete  masonry blocks for reduction of the  tone weight of the structure. 

Que1.13. bandy the characteristics of good  summations. 

Answer  Following are the characteristics of good  total  1. It should  rather be boxy or  globular in shape and of limiting  porosity.  2. It should be chemically inert and not be soft and  pervious.  3. It shouldn’t absorb water  further than 5.  4. It should have rough  face.  5. It shouldn’t reply with cement after mixing.  6. It should be durable and strong.  7. It must be clean i.e., it should be free from lumps, organic accoutrements  etc.  

Que1.14. Compactly describe the physical mechanical and thermal   parcels of  summations in concrete. 

Answer  Physical parcels of Aggregate  1. Grading It’s the  flyspeck- size distribution of an  total as  determined by a sieve analysis using  line mesh sieves with square  openings.  2. Fineness Modulus The result of aggregate sieve analysis is expressed  by a number called fineness modulus.  3. Flakiness Index It’s the chance by weight of  patches in it  whose least dimension is  lower than three- fifth of their mean dimension.  4. extension indicator It’s the chance of weight of  patches whose   topmost dimension is lesser than1.8 times their mean dimension.  Mechanical Assets of Aggregate  1. Aggregate Crushing Value It gives a relative measure of the  resistance of an  total to crushing under a gradationally applied  compressive  cargo.  2. Aggregate Impact Value It gives a relative measure of the resistance  of an  total to  unforeseen shock or impact.  3. Aggregate Bruise Value It gives a relative measure of resistance  of an  total to wear when it’s rotated in a cylinder along with  some abrasive charge.  Thermal parcels of Aggregate Following are the thermal   parcels of aggregate  1. Measure of Thermal Expansion The measure of thermal  expansion of the concrete increase with the measure of thermal  expansion of  total. The measure of expansion of the aggregate  depends on the parent  gemstone  2. Specific Heat It’s a measure of its heat capacity.  3. Thermal Conductivity It’s the capability of the  total to conduct  the heat.  

Que1.15. Explain the bulking and soundness of  summations. 

Answer  Bulking of Fine Aggregate 

1. The increase in the volume of a given mass of fine  total caused by  the presence of water is known as bulking.  Cement product & summations 1 – 18 D( CE- Sem- 5)  2. The bulking of fine  total is caused by the  flicks of water which  push the  patches  piecemeal. 

3. The extent of bulking depends upon the chance of  humidity present  in the beach and its fineness. 

4. It’s seen that bulking increases gradationally with  humidity content up to  a certain point and  also begins to  drop with  farther addition of  water due to the  coupling of  flicks, until when the beach is  submersed. 

5. With ordinary beach the bulking  generally varies between 15- 30.  6. In extremely fine beach the bulking may be of the order of 40 at a   humidity content of 10 but  similar beach is  infelicitous for concrete.  Soundness of Aggregate  1. The soundness indicates the capability of the  total to  repel  inordinate  changes in volume due to changes in environmental conditions,e.g.  freezing and thawing, thermal changes, and interspersing wetting and  drying. 

2. The  total is said to be unsound when volume changes result in  the deterioration of concrete. 

3. This may appear in the form of original scaling to  expansive  face cracking  or to decomposition over a considerable depth, and  therefore vary from an   disabled appearance to a structurally dangerous situation. 

4. IS 2386( Part- V)- 1963 describes a  system to determine the resistance  to decomposition of  summations by  impregnated  result of sodium sulphate  Na2SO4) or magnesium sulphate( MgSO4). 

5. According to IS383-1970 the average loss of weight after ten cycles  should not exceed 12 and 18 when tested with sodium sulphate and  magnesium sulphate, independently.   Que1.16. What are the  goods of the shape and texture of   total on the strength and plasticity of concrete?  Answer  Effect of Shape 

1. Rounded  summations are suitable to use in concrete because  short and  elongated  patches reduce plasticity, increase water demand and  reduce strength. 

2. In the case of angular  patches, the bond between aggregate  patches  is advanced due to interlocking but due to advanced  face area, angular   patches increase water demand and  thus reduce plasticity.  Effect of Texture 

1. This affects the bond to the cement paste and also influences the  water demand of the admixture. 

2. Smooth It improves plasticity but bond between cement paste and   total is weak.  3. Rough It reduce plasticity but bond between cement paste and   total is strong. 

4. face texture isn’t a  veritably important property from compressive  strength point of view but  total having rough  face texture  perform better under flexural and tensile stresses.

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