what is plain cement concrete

  Plain Cement Concrete.

 The mixture of cement, sand and coarse aggregate are generally called plain cement concrete (PCC). . It is also defined as Cement Concrete or Blinding Concrete.
The main reason of providing PCC is to provide a rigid impervious bed to RCC in the foundation before starting any RCC or masonry work directly on the excavated soil, PCC is done to form a leveled surface and to avoid laying concrete on soil directly so as to avoid mixing with soil and also to prevent soil extracting water from RCC thereby weakening it.

Note :-

• Portland Pozzolona cement (PPC) is normally used for Plain cement concrete.
• Compressive strength od PCC varies from 200 to 500 kilogram/square centimeter
• The size of the aggregate used for PCC varies from 10 mm to 40 mm depending on where they are to be used.
• For PCC slump 75 mm to 100 mm may be allowed for foundation work.
• The proportioning is done based on the requirement or given specification. Generally 1:2:4 or 1:3:6 mix is used.
• In volume batching, coarse aggregate and sand shall be measured by measuring box of 30cmx30cmx38cm of a suitable size equivalent to one bag cement of 1/30 m3or 0.035 m3.
• The quantity of water to be used for each mix of 50 kg cement to give the required consistency shall be as follows:
• Not more than 34 lit – 1:3:6
• Not more than 30 lit – 1:2:4
• Not more than 27 lit – 1:1 ½:3
• Not more than 25 lit – 1:1:2
• The PCC is laid in the layers of not more than 150mm thick 
• After 24 hours of laying PCC, moist the concrete surface by flooding with water or by covering with moist gunny bags at least for seven days.
• A strength of PCC is defined as compressive strength after 28 days, expressed as M15, M20, where M stands for Mix and 15 stands for 15 N/mm2 compressive strength at 28 days.
• Do not pour concrete in the pit from a height of more than 1.5 m.
• Do not allow extra cement mortar on top of PCC. for smooth finishing.

How do you calculate the quantity of cement in PCC ?