Characterization of the Tunisian phosphogypsum and its valorization in clay bricks

This study concerns the analysis of the incorporation of phosphogypsum (PG) into the fired clay bricks. In Tunisia, for several years, a set of phosphoric acid production factories have produced PG in large quantities (approximately 10 million tons per year). Currently, in Sfax (Center-East of Tunisia), the PG is stored into piles in the vicinity of the factory, by dry or wet process. The storage of PG, even though presenting a low radioactivity, causes pollution to the watertable and to the soil (due to the infiltration of acid and heavy metals). After characterization, the Tunisian PG, which plays the part of a grease-remover, was introduced into the clay bricks with different mass percentages of 0%, 5%, 15%, 25%, 30% and 40%. The study involved physical, chemical, mechanical and environmental tests on the obtained bricks.The obtained results showed that with 30% of PG incorporation, the bricks successfully satisfied the standard requirements. The increase of the percentage of PG resulted in a decrease in the mechanical strengths of these mini-bricks, but it is still higher than the standards limits. The 25% ratio of substitution appeared to be the most effective considering the performed tests.