What is a quantity of cement and sand for a 748 sq.ft area roof cc???

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One has to know (Neglecting quantity of reinforcement for normal work )
  1. the mix proportion of ingredients in concrete,
  2. and or quantity of cement (kg) per cubic metre,
  3. type of cement (as specific gravity of cement is different for OPC, PPC and PSC)
  4. thickness of slab (to find the volume)
  5. and the expected wastage while handling (lead and lift, type of transportation from mixing to placement)
In general for 748 Sq. Ft area of slab, considering with 300 kg/cu.m of cement, then for 1 inch thick slab, it requires and average of 11 bags of cement. If it is 4 inch thick, it will be 44 bags, and if 5 inch thick, it will be 55 bags. (without considering wastage and without deduction for reinforcement)
Regarding sand, assuming twice the weight of cement, then it requires 44x2x50 to 55x2x50 kg, i.e., 4400 kg to 5500 kg of dry sand. When computed volumetrically, assuming density as 1500 kg/cu.m, requires around 2.93 cu.m to 3.66 cu.m (i.e, 2933 litres to 3666 liters) of dry sand.
As sand contains impurities like pieces of stones, wood, clay lumps, it has to be sieved, which reduces the quantity, hence additional quantity of sand has to be procured.
Wet sand will bulge (called as bulking of sand) in the presence of moisture and hence more sand by volume is required. Medium sand will bulge by around 25% for around 6% moisture (by weight of sand). Hence quantities shall be increased by 25%.

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