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Construction material: Steel

Steel is probably the most versatile comnonly used structural material. Not only is its versatility apparent in great varlety of structures or which it is used but also in many different of structural steel of interest to the designer can be described by the behavior of steel during a simple tension test. The essential elements in steel are metallic iron element non-metallic carbon, with small quantities of other elements such as slicon nickel, manganese chromium and copper. It is thus an alloys.  Though steel is usually more than 98% iron, with other element present in same quantities, these other element have pronounced effect on the properties of steel. Various iron - carbon alloys used as structural material are of three types (I) Cast iron (I) Wrought iron (Ill) Steel cast iron Steel cast iron a low carbon content, while wrought iron has high carbon content. In many ways steels are intermediate in carbon content, between cast iron and wrought iron. The approx...
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How to check the quality of cement on site?

The bad quality of cement reduces the strength of concrete, thereby affecting the service life of structures.
Construction with bad cement always leads to the waste of money and at times it may also cost the safety of the owners.
The quality of cement must be checked at site by the site engineer to ensure it is upto the mark or not.

To make it easier to understand let's categorised it into the following test.

TEST 1: CHECK THE MANUFACTURING DATE OF CEMENT.

  • It is mostly present at the back of the cement bag.
  • It is important to chek the date as the strength of the cement reduces with age.
  • Fresh cement as the property of absorbing the moisture present in the atmosphere quickly.
  • The cement in the bag absorbs the moisture present in the air and the initial setting time takes place and cement will start to loose its strength gradually.
Following table shows the loss in strength due to age
It is always recommended that always use the cement bag before 3 months of its production

TEST 2: PRESENCES OF LUMPS
  • Open the bag of cement and take a good look to it ensure that you fo not see any lumps
  • Lumps are formed when packed cement bags come in contact with moisture.
  • If you find lumps in the bag then that bag should be rejected

TEST 3: FLOAT TEST

  • The excess amount of dust present in the cement reduces the strength of cement
  • To check the presence of fust take hand full of cement and throw it in the bucket full of water
  • If the cement floats on the water for some time before it sinks then it is a good quality cement
  • But if it sinks immediately into the water then it indicates bad quality of cement

TEST 4: COLOUR TEST
  • Colour of the cement gives the indication of presence of excess lime or clay and degree of burning
  • Generally cement as a dark greenish grey colour
  • The light grey colour indicates that the cement may be older one or it may be in attack of moisture

TEST 5: TEMPERATURE TEST

  • CEMENT as a tendency to remain cool while in the bag
  • This means if you touch the cement you will feel cool
  • If it is worm inside it indicates the process of hydration as taken place and it is a good quality

TEST 6: CEMENT ADULTERATION TEST

  • ADULTERATION means making something poorer in quality by addition of another substance
  • Cement is a very fine in nature when you rub the cement between the fingers you will feel smooth 
  • However if you feel gritty or feel rough it means that silt or clay is present in the cement which may lower the strength of cement

TEST 7: ODOUR TEST

  • The presence of clay and silt can be evaluate by smelling of cement 
  • If cement contain too much of mounted clay and silt as an adulterant the past will give an earthy smell

TEST 8: STRENGTH TEST

  • A block of cement 25×25×200 mm long is prepared and is immersed for 7 days in water it is then placed on support 150 mm apart
  • Then loaded it with 34 kg weight if block doesn't show any failure then it indicates the good quality of cement




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