Please tell me what quantity of water should be added for slab casting in concre

Dear Piyush

   The quantity of required water is following.

1.Water for nominal mix concrete shall generally be equal to 5% by weight of aggregate and 30% by weight of cement.

2.Generally for vibrated concrete the quantity of water will be less by 20% but the actual quantity shall be determined by the field test for slum.

3.For one bag mixture, 32 liters of water is required and the ratio will be 1:2:4 

4.For one bag mixture, 30 liters of water is required and  the ratio will be 1:1.5:3 , for more information about cement concrete please visit gharexpert construction section concrete sub section.