How to build a concrete block water tank

 

Water Tank may be constructed using Concrete Blocks Using Following Construction methodology.

1- First of all we should work calculate size of water tank as per required capacity.

Suppose we want to construct 50 thousand US Gallon capacity tank on Ground surface using block masonry with cement sand mortar (1:3) ,now the main thing is how much Length and width should be adopted for the construction of water tank. It is needed to understand that  if we increase the area by increasing the length and width of tank it's depth will be decreased and if we decrease the size or area of tank its height will be raised.

Now we will equate the height  of wall with reasonable thickness of wall so let's have some calculations regarding suitable construction of water tank.

Capacity of water tank = 50000 US-Gallons

Volume of Water Tank As per 50000 US-GALLONS= (50000x3.78)/28.32= 6674 Cft

Volume of water tank = Length x Width x Depth

Say we have feasible size of 40 Ft x40 Ft

6674Cft =  40Ft x40Ft x Depth

Depth     = 4Ft-2 Inch

Next Step is Calculation of Horizontal Pressure Using following formula

P = (w.H.H)/2

Here    w= Density of water in Pound/Cubic Foot

H= Depth of water in Feet

P= Horizontal Pressure in Pound/ Rft of wall

Putting the available values

Pressure =( 62.4x4.17x4.17)/2 = 543 Pounds

 

We know that maximum pressure acts at H/2 OR H/3 So Adoption value of H/2 we will proceed for further steps to decide wall design using concrete blocks.

We will design concrete blocks wall using maximum pressure at H/2 .

Maximum Pressure = Weight of wall

543 Pounds = Length x Width x Depth x Density of Block Work

543 = 1ft x Width x 4.17 Ft x 130 Pound/ Cft

Width = 1 Ft

Factored Width of wall will be 2 Times of wall width at Maximum Pressure

Width = 2 ft.

2 ft width will be continued up to the depth of 2 ft and then it will be gradually decrease to produce 1 ft width at top of wall .

The Ground bearing capacity has been found as .65 Ton/Sft

So we can check feasibility / Suitability of Bearing capacity according to the weight of water tank.

According to following designed data

1- Excavated depth to approach the ground surface where bearing capacity is .65 Ton /Sft is 3 Ft.

2- Supply and lay Pcc (1:3:6) concrete 3" thick

3- Supply and lay Rcc (1:2:4) concrete 6" thick

4-Construction of block masonry (1:3) using Cement sand mortar as shown in figure. A.

5-Supply and apply cement sand plaster (1:2) 3/4" thickness complete in all aspects.

Check feasibility of bearing capacity of ground at  block wall line

 

Weight of wall = 1 x 2x2x130          = 520 Pounds

    Weight of wall =1x(1+2)/2x130    =195 Pounds

Weight of PCC = 1x2x.25x140         =70 Pounds

Weight of RCC = 1x2x0.5x140         =140 Pounds

 Total Weight      = 925 Pounds per 2 Sft under wall area

So Load per SQ.FT In Pounds =   462.5 Pounds Per Sft

So Load per SQ.FT In Tons =   462.5 /2240 = 0.2 Ton/Sft

So it is very safe load against bearing capacity of ground

Now we will make a safety check in water portion  

Weight of PCC = 1x2x.25x140         =70 Pounds

Weight of RCC = 1x2x0.5x140         =140 Pounds

Weight of water = 1x1x62.4x4.17     =260 Pounds

Total Weight in pound/Sft     = 470 Pounds per Sft

Total Weight in Ton /Sft     = 470 /2240 = 0.2098 Ton/Sft

So it is also very safe load against bearing capacity of ground.

Now we can start construction in following ways

1- Excavation of soil including shifting of surplus soil having lead of 500 Ft and Lift up to 7 Ft complete in all aspects

2- Provision of 100 % compaction including cut and fill up to 6 inch using road rollers complete in all aspects.

3- Provide and lay PCC (1:3:6) 3 inch thick using good class of cement ,sand , crush and water complete in all aspects

4- Provide and lay RCC (1:2:4) 6 inch thick using good class of cement ,sand , crush and water .Use 1/2" dia bars @ 9" c/c both ways and complete in all aspects.

5-Construction of Block wall using cement sand mortar (1:3) Complete in all aspects.

6-Supply and applying of cement plaster (1:2)  3/4" thick using good class of cement and sand ,complete in all aspects.

7- Supply and lay Pcc(1:2:4) concrete on wall and bed joint in 45 degree angle slope including float finishing and use of admixture to gain water tight concrete.