Hydraulicity of Lime Mortar with Surkhi

Surkhi is a fine powder obtained by grinding burnt clay bricks or tiles. It is added to lime mortar to impart hydraulicity. The addition of surkhi to lime mortar produces a hydraulic lime mortar, which has better properties than non-hydraulic lime mortar. The following points explain how surkhi imparts hydraulicity to lime mortar:

Chemical Reaction
When surkhi is added to lime mortar, it reacts with the calcium hydroxide present in lime to form calcium silicates and aluminates, which impart hydraulicity to the mortar. These compounds are responsible for the setting and hardening of the mortar.

Improved Strength
Hydraulic lime mortar has better strength and durability than non-hydraulic lime mortar. The addition of surkhi improves the compressive strength of the mortar, making it suitable for use in load-bearing structures.

Reduced Shrinkage
Hydraulic lime mortar with surkhi has reduced shrinkage compared to non-hydraulic lime mortar. This is because the hydraulic compounds formed by the reaction of surkhi with lime have better bonding properties and prevent the mortar from shrinking.

Faster Setting Time
Hydraulic lime mortar with surkhi has a faster setting time than non-hydraulic lime mortar. This is because the hydraulic compounds formed by the reaction of surkhi with lime set and harden quickly, leading to faster construction.

Conclusion
In conclusion, surkhi is added to lime mortar to impart hydraulicity, which improves the strength, durability, and setting time of the mortar. It also reduces shrinkage and makes the mortar suitable for use in load-bearing structures.