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How to calculate the materials for a circular RCC water tank

In this illustration we will calculate cement, sand, crushed stone and of course steel for given water tank.

RCC has 1:2:4 with 15 cm thickness
PCC has 1:2:4 with thickness equal to 10 cm
The slab is RCC having 1:2:4 with 10 cm thickness

And of course there is a hole and the hole is circular with diameter = 60 cm
The depth is equal to 3 cm
The steel is 1% and #4 bar will be used

Solution:

Diameter = 4 meter + 2(15 cm) + 2 (10 cm) = 4.5 m = external circle diameter
PCC work = πD²/4 * T = π (4.5)²/4 * 0.1 = 1.59 m³
Assume the base or floor as S1 and wall as S2
D2 = 4 meter + 2(15 cm) = 4.3 m
The next approach is the RCC work in wall S1 = π (D1)²/4 * T = π (4.3)²/4 * 0.15 = 2.178 m³
RCC work in wall S2 = π ((D1)² – (D)²)/4 * d = π ((4.3)² – (4)²)/4 * 3 = 5.867 m³
RCC work in slab = π (4.3)²/4 * 0.1 = 1.452 m³
Deduction for hole = π (0.6)²/4 * 0.1 = 0.0282 m³
RCC work in Slab – Deduction for hole = 1.423 m³ = net quantity of RCC slab
Total RCC work = 2.178 m³ + 5.867 m³ + 1.452 m³ + 1.423 m³ = 9.468 m³
Steel = 1/100 * 9.468 = 0.09468 m³ * 7850 kg/cu.m (is the unit weight of density of mild steel) = 744 kg
Total net RCC = 9.468 m³ - 0.09468 m³ = 9.373 m³

Total PCC work (1:2:4) = 1.59 m³ + 9.373 m³ = 10.963 m³

Let’s calculate cement, sand and crushed stone work
Material = ratio of material/sum of ratio * dry volume
Ratio is 1:2:4 and sum of ratio is 7

Dry volume = wet volume * 1.54
Wet volume = 20*12*0.5
Wet volume = 120 CFT
Dry volume = 120 * 1.54
Dry volume = 184.8 CFT

Cement = 1/7 * 184.8 =26.4 CFT
Cement = 26.4/1.24 = 21.12 bags
Sand = 26.4 * 2 = 52.8 cft/100 = 0.528 sacra

Bajri = 26.4 * 4 = 105.6cft/100 = 1.056 sacra
Crushed stone = 6/10 * 770 = 462 CFT
= 462/100 = 4.62 sacra

To learn the complete process, watch the following online video demonstration.

Lecturer: SL Khan