Civil Engineering - Estimating and Costing - Discussion

Wet volume of concrete.

Area = 100 m^2.
Thickness = 4 cm = 0.04 m.
Wet volume = 100 × 0.04 = 4.00 m^3
Allowance for uneven surface/base.
Add 10% extra = 4.00 × 1.10 = 4.40 m^3.

Dry volume of concrete.

For concrete work, increase wet volume by 50% (or a factor of 1.5) to account for bulking/voids in dry materials.
Dry volume = 4.40 × 1.5 = 6.60 m^3.

(Some references use 1.54 factor directly on wet volume without the 10% step, giving ≈6.16 m^3, but the 10% + 50% combination is common in many exam/estimation contexts and yields 6.6 m^3.)
Proportion of cement in 1:2:4 mix.
Total parts = 1 + 2 + 4 = 7 parts.
Cement proportion = 1/7.

Volume of cement.
Cement quantity = Dry volume × (1/7) = 6.60 × (1/7) ≈ 0.942 m^3 ≈ 0.94 m^3.

Area = 100 sq.m.
Thk= 4 cm = 0.04 m.
V=A*Thickness = 100 * 0.04 = 4 cu.m.
Extra increase for dry volume = 1.55 * 4 = 6.20 cu.m.
Qty of cement in(1:2:4) = 6.20* 1/(1+2+4) = 0.88 cu.m.

The volume of concrete= 100 * .04 = 4.
10% increase for the unevenness + 50% increase for dry volume =4*1.1*1.5 = 6.6cum,
Cement=6.6/(1+2+4).

The correct answer is 94.
Volume of wet concrete in 4cum.
Volume of dry concrete is=4*1.54( constant),
Total v= 6.61.
Quantity of cement = 1/7 * 6.61 = 0.94.

The answer is 0.88m^3.

100 * .04=4cu.m of wet concrete.

To produced 1cu.m of concrete 1.54cu.m of dry concrete required.

1.54 * 4 = 6.16cu.m
6.16/1+2+4 = .88 cu.m of cement reqd.
.88 * 1440 (density of cement)=1267.2 kg.

Or,
1267.2/50kg = 25.34=26 bag of cement.

The correct answer is 0.88m3.

For 4cm thick flooring constant of rate analysis is 6.6.
6.6/(1+2+4) = 0.94285,

for 2.5cm thick flooring 4.125.

1.54 is the conversion factor to convert wet to dry mix and additional they take 10% for unevenness & loss. So, total 1.64.

0.88 m^3 is the right answer.