Traditionally, less importance has been given to mortars as compared to concrete. However, as construction activity is steadily on the rise, the time has come to take a fresh look at making use of technology for making plaster.
The construction industry uses naturally occurring materials along with manufactured items like steel and cement. However, with rapid strides in urbanisation, naturally occurring materials are depleting fast and the industry is seriously thinking of replacing these naturally occurring materials with manmade materials. Various kind of mortars use sand as one of the important ingredients along with cement. In the years to come, this specific application of cement will undergo a sea change, in the way in which it is produced and applied. Let?s take a look at the dry mix plaster mortar business from the manufacturer?s perspective.

In Europe, after the Second World War, Germany was devastated? it turned to the dry mix mortar concept for reconstruction, and greatly benefited. This concept got a boost, thanks to the invention of dispersible polymers by Dr Wacker Alexander in 1957. This invention made available polymers in powder form. It became the backbone of value-added dry mix mortars, and Germany is now considered to be the capital for such mortars globally.

Before we examine the application of this mortar in the Indian context, let us first understand the nature of this mix. Generally, mortars are used in masonry for joining stones, bricks, blocks etc., and plasters are used for rendering on the outside and inside of walls. The differences between mortar and plaster lie in the capacity of plasters to take better finish, which depend to a very large extent on the type of sand used in the mix and the ratio of sand to cement.

For plasters, we use finer sand. However, the term ?mortar? is also used loosely to refer to both plasters and mortar. So far, the practice in our country has been to mix sand and cement at a site manually, either on the ground or in a tray to get plaster mortar. There have been certain issues in the practice followed ?primarily, the mixing not being proper, ingredients not getting dispersed uniformly and excessive usage of water. Today good quality sand is not available for making plaster mortar, due to environmental restrictions. The use of construction chemicals in making plaster mortar is on the rise. However, applying the mortar on walls or concrete is yet another problem. Application largely depends on the skill of the mason, the surface on which plaster is applied, etc. Generally, outside plaster is done in one or two coats, depending on the thickness of the plaster.

In areas like Mumbai and surroundings, where the rainfall is high, the quality of external plaster has to be extremely good. There are different grades of mortar that can be used for plastering of structural members such as in CM 1:2, 1:4, 1:6, 1:8, etc. The number indicates the ratio of cement to sand in volumetric proportion. In the case of plaster, the skills of a mason are more important than the product itself. The cement and sand mix ratio should be 1:6 (1 cement: 6 sand) for internal plastering of bricks and 1:4 for external plastering. Never do a plastering beyond 12 or 15 mm thickness on a brick wall. Avoid plastering beyond 6 mm thickness on concrete in one go. The hacking should be done on the smooth surface like ceilings and columns before plastering work.

Today, factory-made mortar is costlier by about 30 per cent than site-made mortar. However, factory-made mortar is far superior in quality than site-mixed mortar. In the issues to come, we shall cover more details on factory-made plaster mortar.