# VINDEX PLASTER

It is harder to crack prejudice than an atom. (Albert Einstein)

Prejudices on plaster as a building material are countless and senseless resulting from ignorance on the subject and clichés referring to a few special cases. In effect, commonly, it is thought that there exists only one type of plaster which is the scagliola. However there are different types of plaster ranging from those tender up to extremely hard and resistant enough to be used in the production of the prosthesis.

Plaster is one of the building materials used in antiquity but, over the centuries, has been abandoned in favor of the lime which in turn was abandoned in favor of the cement. So research into the use of plaster as a building material was stopped almost by the industrial revolution. Nowadays its use as a building material is very limited.

Recently, thanks to a greater sensitivity towards sustainable and ecological building materials plaster begins to be seen with some interest. In fact, the is ecological par excellence, its pH is comparable to that of human skin, the same can be said about its heat conductivity, so we use it for fractures bandage and dental use. Gypsum has beenn used at school to write on blackboards around the world for long time.

The gypsum-based building materials, such as bricks vindex are great for creating environments with ideal microclimate maintaining a temperature and relative humidity controlled naturally.

Vindex plaster + white sand yellow desert (South West of Tunisia) for the production of vindex bricks.

Building plaster is very economical to produce, a natural product, environmentally friendly, sustainable and has excellent characteristics for thermal and acoustic insulation and in many cases could be used instead of cement. In fact, the TAVX normally uses the building plaster instead of cement.

## Vindex Plaster

Vindex Plaster GVX is an alpha type anhydrite but also contains a small part of the beta type, produced by the firing of gypsum, appropriately crushed, at a particular temperature and pressure. The GVX is the main binder in vindex constructions.

p> Vindex plaster is produced by calcination of the gypsum in two consecutive steps: the first stage is the production of gypsum semi-hydrate ie:
$$C_aSO_4.2H_2O\;[128^oC] \rightarrow C_aSO_4.1/2H_2O + 3/2H_2O$$
The second stage is the formation of gypsum completely dehydrated:
$$C_aSO_4.1/2H_2O\;[250^oC] \rightarrow C_aSO_4\;(anidrite) + 1/2H_2O$$.

(1):In technical nomenclature this kind of plaster is also called anhydrite.