Viabilidade técnica da utilização de diferentes proporções de gesso e fosfogesso como material de construção

Abstract

The phosphogypsum, a radioactive residue derived from the fertilizer industry, in addition to being produced 4 to 6 times more than phosphoric acid, doesn’t have an appropriate disposal, usually being stacked in vast areas. Utilizing this residue as a total or partial substitute for gypsum as a building material would benefit both the fertilizer industry and the construction industry, reducing the exploitation of gypsum, a natural resource. This study aims to analyse the technical feasibility of using different proportions of gypsum and phosphogypsum in the construction industry. To accomplish this objective, physical, mechanical and radiological tests have been conducted, and its results analysed according to national and international norms as well as previous studies. Based on the physical and mechanical characterization it can be concluded that using phosphogypsum is impracticable, seeing that the material neither presents a defined trend line nor meets the minimum required in national standards. The only exception being the dry unit weight, where it was established that proportions containing up to 21,5 percent of phosphogypsum would attend the minimum required. The materials compression strength reached peak points of 5,4 ± 0,4 MPa when mixed in any proportion to phosphogypsum. The hardness test reached maximum of 8,7 ± 0,7 N/mm². The characterisation may have been influenced by the gypsum’s possible low quality, since it didn’t meet the requirements even on its own. The radiological analysis found results inferior to the limits established by national and international organs. Maximum radon concentration indoor was found to be 147 ± 26 Bq/m³, while for maximum equivalent radium activity indoor was 5,7 ± 1,7 Bq/kg, allowing its use without any health concerts to the general population.