Auroville has an abundance of red soil, and it can be used in the construction in a lot of ways. One of the ways in which we use this material is for plastering the wall. While digging the foundations there is heaps of soil lying around, the consistency and texture depend from place to place.
We use this soil instead of sand, depending on the density this soil can be used in the plaster mixture. Recently this technique was used in a couple of projects. The process goes like as follows:
The big lumps of red earth are broken down into smaller portions and then sieving it into fine particles
Then the same process goes for M-sand
Now the fine red soil, M-sand, and cement is mixed in the ratio of 1:3:3 (1 portion of cement - 3 portions of red earth - 3 portions of M-sand)
This mixture can be used for plastering the walls
The result after drying is a textured finish with a tint of red in it which looks great and can be left exposed, as it blends with the surroundings. It can also be painted and it holds the paint very well because of the texture. We avoid using the use of river sand and use materials which are locally available or don't harm the environment.