Description
The plaster cast are widely used in building to the finishing of interior, because the acoustic properties, thermal, electrical and, especially, as a product of relatively low cost. Plaster Pole of Araripe at semi-arid region, achieves 90% annually of the Brazilian plaster production, gypsum ore and its products, estimated at around 2 million tonnes. There are now in Plaster Pole more than 150 plants in plaster cast and the main products are the panels and blocks. These plaster casts are produced through a process of hydration of the plaster, using specific molds. Are characterized by being made of fragile material, which have low compressive strength, flexural and impact. It is also known that the mechanical characteristics of these casts depend on several factors, such as: the nature of used plaster, the factory process, the consistency (water/plaster weight ratio) and the presence of additives. The
introduction of these latter, in turn, reflected in the increase of cost of the final product and makes the recycling of pre-molded after use, without improving the strength of them. In were modified this work, the mechanical properties of plaster cast from the reduction of the water/plaster and molding of wet powder with aid of hydraulic pressing, as there is published in patents. However a central composite rotational design (CCRD), Surface Analysis Method (SAM) and micrographs were used to
explain and define what the appropriate ratio water/plaster to produce plaster cast high mechanical strength. Scanning Electronic Microscopy (SEM) showed an elongation of the crystals and storage, in the form of parallel beams, and a significant reduction of porosity in the microstructure of the material after shaping by pressing. The CCRD showed that when the water/plaster ratio close to 21.0% (stoichiometric
value) reduces the contribution of re-hydration of the semi-hydrate in increasing of mechanical strength
