# PARAM VISIONS

All about civil construction knowledge- PARAM VISIONS

### Wet & dry volume of cement mortar - its calculation.

#### 1. What is the dry & wet volume of the cement mortar?

The dry volume of the cement mortar is formed by mixing cement and fine aggregates (sand), without adding water to them.

When we add water to these dry mortar ingredients, as per the required proportion, and mix thoroughly, the resulting mixture is said to be the cement mortar's wet volume.

#### 2. What is the dry volume of 1 cum. of wet cement mortar?

To calculate the dry volume of the cement mortar, we have to add 33% extra to the wet mortar mix.

So, the dry volume of the mortar = wet volume + 33% wet volume.

= 1cum + 33% of 1 cum.

= 1 + (33÷100) × 1

= 1 + 0.33 = 1.33cum.

So, for 1cum. of wet cement mortar, we have to take 1.33 cum. of dry mortar mix.

#### 3. Why we have added 33% extra in the dry mortar mix?

While preparing the dry mix for the mortar, the ingredients we add are loosely packed with voids in them. Generally, the sand contains 23 to 27% voids in them and when we add water to this dry mix, the air particles in the voids are removed and the mortar gets compacted forming a homogeneous mix. The wet mix so formed shrinks by 23 to 27% of the dry volume of the mortar.

Let us consider 25% shrinkage in the dry mix of 1 cum, after adding water as shown in the above fig.

So, 1cum of the dry mix = 0.75cum of the wet mix.

Now, we will calculate the volume of the dry mix required for the 1 cum of wet mix.

i.e. for 0.75 cum of wet mortar = 1cum of dry mortar

So, for 1cum of wet mortar     = __ cum of dry mortar?

1cum of wet mortar  = (1cum × 1cum )÷ 0.75 cum

= 1.33cum of dry mortar.

While estimating the volume of materials in the construction, we calculate the wet volume of the mortar. We have to multiply that wet volume by 1.33 to get the dry mix of the mortar.

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