In my previous articles i have been using the conversion factors for converting wet volume to dry volume.


This article is about the conversion factor 1.54 used to calculate the dry volume of concrete mixture. i.e, to convert wet volume of concrete to dry volume, we multiply the wet volume by a factor 1.54.

The main concept is that, on addition of water the particles of dry concrete mixture slide over one another due to the loss of friction between particles as the water acts as a lubricant between the particles resulting in readjustment of particles in a closely packed pattern reducing the volume occupied by the voids and hence reducing the volume of concrete mass.

 
The percentage of voids due to fine aggregate present in concrete is 20% and the percentage of voids due to course aggregate is 32 to 34% summing upto a total of 52 to 54%. Therefore we need an extra 54% dry concrete mixture for casting any wet volume of concrete. 


Moreover it has been seen that the dry volume of concrete required to obtain 1m³ of wet mass is 1.54m³ of dry concrete. This is where we get the conversion factor. 
So to obtain 1m³ of wet concrete we need to have 1.54m³ of dry concrete mixture available. 

For illustration let's consider a concrete cube of length 1m, breadth 1m and height 1m.
Volume of concrete cube = 1x1x1 = 1m³ (wet volume) 
To convert this wet volume to dry volume, the volume is increased by 54% of wet volume. 

Dry volume = wet volume + 54% of wet volume. 
Dry volume = 1 + 54/100 x 1 = 1+0.54x1 = 1.54 x 1m³

Hence dry volume of 1m of wet concrete = 1.54 x 1m³

Dry volume of "n" m of concrete = 1.54 x n m³
Where, n = wet volume of concrete. 

Example: 
suppose we need to cast a concrete slab of area 900sq ft. 
Let the thickness of slab be 6'' i.e, 0.5ft
Total volume of slab = area x thickness of slab = 900 x 0.5 = 450Cft

It should be noted that this total volume is the wet volume of the slab. So to convert this wet volume to dry volume we will add extra 54% of wet volume to it or simply we will multiply the wet volume by 1.54 to get the dry volume.

Hence, 
Dry volume = 1.54 x n
Here n = 450Cft
Dry volume = 1.54 x 450 = 693Cft

Alternative solution:
Dry volume = wet volume + 54% of wet volume 
Dry volume = 450 + 54% of 450 = 450 + 0.54x450 = 693Cft