Cement Concrete Raw Material

The following points should be kept in mind while collecting raw materials for cement concrete in construction work.

Cement

       Cement is the most important raw material used in construction of a building. You can ensure the quality of ‘Cement’ with following guidelines.

            Fine aggregate/ coarse sand consists of natural sand, crushed stone sand or crushed gravel stone dust. The quality of the sand has more impact on the strength of the structure in spite of the quantity of the cement used.
 If there is more silt in coarse sand, the strength of cement mortar is reduced from 1%to30%.
 If you take best quality coarse sand, it will give maximum strength. You can ensure the quality of Fine aggregate with following guidelines.

• It should be hard, durable chemically inert, clean and free from organic matter, not containing any appreciable amount of clay balls or pellets and other harmful impurities i. e. alkaline, salt, mica, decayed vegetation, lumps etc.
• It should be passed through I. S. Sieve 4.75 MM. It should have the finest modulus 2.50 to 3.50 and silt contents should not be more than 4%. Coarse sand should be either river sand or pit sand; or combination of the two.
• It should be obtained from Badarpur Sand or Stone dust obtained by crushing hard stones or gravel. It should also be obtained from river bed such as Tajewala, Dadupur sand.
• The sand particle should be coarser and have minimum silt contents. The silt contents should not be more than 4%.
• It should be according to the size/specification and free from mud, clay, organic matter and other foreign matters. 

Coarse Aggregates

             Coarse Aggregate or bazri consists of natural occurring stones (crushed, uncrushed or broken). The quality of the Coarse Aggregate or bazri has more impact on the strength of the structure in spite of the quantity of the cement used.
 If you take best quality coarse sand, it will give maximum strength. You can ensure the quality of Coarse Aggregate with following guidelines.

•  It should be hard, strong, dense, durable, and clean.
• It must be free from veins, adherent coatings and injurious amounts of disintegrated pieces, alkali, vegetable matter and other deleterious substances.
• It should be roughly cubical in shape. Flaky pieces should be avoided. It should confirm to IS: 2383(I).
• The coarse aggregate is clean, hard, non porous, free from lumps of clay and vegetable matter.
• Water absorption of aggregate is not more than 10 % of its weight after 24 hours immersion in water.
• Angular and roughly cubicle particles are ideal. River gravels make the best coarse aggregate.
• Aggregate is chemically inert material.
• The maximum quantity of deleterious materials should not be more than 5% of the weight of the aggregate when determined in accordance with IS: 2386(I).

Water

             Water is one of the most important elements in construction but people still ignore quality aspect of this element. The water is required for preparation of mortar, mixing of cement concrete and for curing work etc during construction work. The quality and quantity of water has much effect on the strength of mortar and cement concrete in construction work.

         It has been observed that certain common impurities in water affect the quality of mortar or concrete. Many times in spite of using best material i.e. cement, coarse sand, coarse aggregate etc. in cement concrete, required results are not achieved. Most of Engineers/Contractors think that there is something wrong in cement, but they do not consider quality of water being used.