Lime's Role in Top Coat Plaster
Lime is frequently added to cement plaster, specifically for the finishing or top coat, to impart key properties essential for a durable and smooth surface.
Primary Function: Preventing Shrinkage
The principal advantage of using lime in the cement slurry for the top coat is to make the plaster non-shrinkable.
- Lime enhances the plasticity and water retention capacity of the plaster mix.
- This improved water retention slows down the drying rate of the plaster.
- Slower drying reduces the overall volume change (shrinkage) as the plaster cures.
- Minimizing shrinkage is critical for preventing the development of fine cracks, which ensures a better final appearance and longevity.
Secondary Benefits
Although lime also offers other advantages:
- It increases the workability of the plaster, making it easier to apply smoothly.
- It can contribute to a brighter finish on the surface.
However, the role of lime in mitigating shrinkage and preventing cracks in the critical top layer is considered its most significant contribution during plastering.
Important Questions from Bricks and Mortar
The Indian standard brick size is
Statement (I): Bricks are soaked in water before using in brick masonry for removing dirt and dust.
Statement (II): Bricks are soaked in water before using in brick masonry so that bricks do not absorb moisture from the bonding cement mortar.
Mortars for masonry construction are designated based on their strength as per IS: 2250 and IS: 1905, with classifications including $L_1, L_2, H_1, H_2, M_1$ and $M_2$. What is the correct sequence representing the decreasing order of strength for these designations?
The mortar mix proportion used in brick masonry is generally taken as
As per Indian Standard, the modular size of bricks is-
