Concrete Technology: Cement Production and Aggregates Unit 1 Part 5

Que1.21. What’s fineness modulus? How is sieve analysis conducted for fine  summations and coarse  summations? 

Answer  Fineness Modulus( FM) 

1. The FM is an  indicator of the fineness of the  total. The advanced the FM  the coarser the  total. FM of fine  total is useful in estimating  proportions of fine and coarse  total in concrete  fusions. 

2. The fineness modulus( FM) for both fine and coarse  summations is   attained by adding the accretive  probabilities by mass retained on  each of a specified series of sieves and dividing the sum by 100.  FM = ( Accretive retained on specified seive)  Beach Fineness Modulus  Fine2.2 –2.6  Medium2.6 –2.9  Coarse2.9 –3.2  Sieve Analysis 

1. This is the name given to the operation of dividing a sample of aggregate  into  colorful  fragments each  conforming of  patches of the same size. 

2. The sieve analysis is conducted to determine the  flyspeck size distribution  in a sample of  total, which we call gradation. 

3. The  summations used for making concrete are  typically of the maximum  size 80 mm, 40 mm, 20 mm, 10 mm,4.75 mm,2.36 mm, 600 micron,  micron and 150 micron.

The aggregate bit from 80 mm to  mm is  nominated as coarse  total and the bit from  mm to 150 micron is  nominated as fine  total.  4. As Per IS 2386( Part- 1) Fine  total 6 standard sieves with  openings from 150 m to4.75 mm.( 150 m, 300 m, 600 m,1.18 mm,  mm,4.75 mm). 

5. Coarse total 5 sieves with openings from4.75 mm to 80 mm. 4.75 mm, 10 mm,12.5 mm, 20 mm, 40 mm).  6. The size4.75 mm is a common bit appearing both in coarse  aggregate and fine  total( CA and FA). 

7. Grading pattern of a sample of CA or FA is assessed by raising a  sample  consecutively through all the sieves mounted one over the other  in order of size, with larger sieve on the top. 

8. The material retained on each sieve after shaking, represents the  bit of aggregate coarser than the sieve in question and finer than  the sieve  over. 

9. Sieving can be done either manually or mechanically.  

Que1.22. Explain different  system of  dimension of  humidity content of  summations. 

Answer  Following are the  system of  dimension of  humidity cement of   summations  1. Drying Method 

i. The  operation of drying  system is fairly simple. Drying is carried out  in an roaster and the loss in weight  ahead and after drying will give the   humidity content of the  total. ,  If the drying is done  fully at a high temperature for a longtime.the loss in weight will include not only the  face water but also some  absorbed water. 

iii. A fairly quick result can be  attained by hotting the aggregate  snappily  in an open  visage.  iv. The process can also be speeded up by pouring  ignitable  liquid  similar  as methylated spirit or acetone over the  total and  kindling it. 

2. relegation system 

i. In the laboratory the  humidity content of  total can be determined  by means of pycnometer or by using Siphon- Can Method. 

ii. The principle made use of is that the specific  graveness of normal  total  is advanced than that of water and that a given weight of wet  total  will  enthrall  a lesser volume than the same weight of the aggregate  when dry. 

iii. By knowing the specific  graveness of the dry  total, the specific  graveness  of the wet  total can be calculated. 

iv. From the difference between the specific  earnestness of the dry and wet   summations, the  humidity content of the  total can be calculated. 

3. Electrical Meter Method  lately electrical  measures have been developed to measure  immediate or  nonstop reading of the  humidity content of the   total. 

ii. The principle that the resistance gets changed with the change in   humidity content of the  total has been made use of. 

4. Automatic dimension 

1. In modem batching  shops  face  humidity in  summations is  automatically recorded by means of some kind of detector arrangement. 

2. The arrangement is made in such a way that the  volume of free water  going with  total is automatically recorded and  contemporaneously  that much  volume of water is reduced.

Que1.23. What are the  goods of  contaminations in the mixing water  on concrete?  


Write a short note on the feasibility of use of  ocean water for mixing  concrete. 

Answer  goods of Mixing Water from Different Sources 

1. Ground Water Presence of sulphates in ground waters  largely   pernicious to concrete foundations. 

2. Sea Water 

i. The  ocean water generally contains3.5 of  mariners with about 75 of  sodium chloride, about 15 of chloride and sulphate of magnesium. 

ii. It has been  set up to reduce the strength of concrete by 10- 20 and  slightly accelerate the setting time.  iii. Sea water may lead to  erosion of  underpinning. 

iv. The chlorides in  ocean water may beget efflorescence in concrete. 

v. The use of  ocean water isn’t recommended for prestressed concrete  because of stress  erosion and the small periphery cables. , particular  If  ocean water can not be avoided for making  corroboratedconcrete.precautions should be taken to make the concrete  thick by using low  water/ cement  rate coupled with vibration and to give an acceptable  cover of at least7.5 cm. 

3. Industrial Waste Water When artificial waste water is used as  mixing water in concrete, the reduction in compressive strength is  generally  lower than about 10. 

4. Water For Washing summations 

i. When  summations are washed with water containing  contaminations, they  get  carpeted with layers of ground,  mariners and organic matters.  ii. These reduce the bond between the  summations and cement and  markedly affect the strength. 

5. Water for Curing  Waters containing  contaminations and leading to stains is  reprehensible. 

ii. When concrete is  subordinated to prolonged wetting, indeed a  veritably low   attention of iron and organic matter may beget staining. 

iii. Water containing  further than0.08 ppm of iron isn’t recommended for  curing. 

Que1.24. Enumerate the  colorful  contaminations in water having   injurious  goods on concrete. 

Answer  contaminations in water can be of following types 

1. Chlorides  Chlorides can beget  erosion of the  sword  underpinning and can  accelerate setting. 

ii. The water used may be  defiled with chlorides because of it  being  ocean water, the presence of  cocktails andde-icing  mariners, or  deliberate chlorination for disinfection. 

2. Sulphates Sulphates can lead to the reformation of ettringite as well  as reduction of long- term strength  situations. 

3. Organic Matter The  goods of organic matter on concrete are varied.  still, it shouldn’t be used because it’ll affect  If algae are present inwater.setting and strength development. 

4. Sugar Sugar retards the setting time. Too  important sugar may ‘ kill ’ the  concrete( i.e., it’ll not set). 

5. Wastewater It’s stylish not to use wastewater. Alternately it can be  used after proper testing and treatment.

Leave a Comment