MECHANICAL PROPERTIES OF PHOSPHOGYPSUM AND TRENDS ITS UTILIZATION

Abstract

Phosphogypsum is a waste obtained by binding calcium in the process of sulfuric acid decomposition of phosphate raw materials in the production of phosphorus fertilizers. The article presents the results of complex laboratory studies of more than 500 samples of calcium sulfate hemihydrate and dihydrate. Calcium sulfate dihydrate (CaSO4·2H2O) is a solid fine-crystalline substance of white or gray color with the inclusion of large aggregates. Deformability, strength properties and permeability of calcium sulfate dihydrate were determined on specially prepared samples with a relative compaction of 0.95; 0.90 and 0.80 by the methods used in engineering and geological surveys. The internal friction angle, cohesion and coefficient of permeability have values typical for silty sands and sandy loam, and the compressibility characteristics are significantly lower due to the solubility of matter. This material is characterized by subsidence and suffusion sediment characteristic of carbonate rocks (dolomite, limestone). Calcium sulfate hemihydrate (CaSO4·0.5H2O) - a loose earthy mass of white or gray color, as the process of hydration and the appearance of cementation bonds turns into a semi-rocky technogenic soil of low strength. The characteristics of calcium sulfate hemihydrate were determined on the undisturbed samples taken from the dump after 1 and 6 months, 1, 5 and 10 years after storage. These characteristics are comparable to construction gypsum materials from lower grades. It is recommended to use calcium sulfate dihydrate as ground material when carrying out water-protective measures and neutralizing the acids contained in it, the use of calcium sulfate hemihydrate is significantly limited by its setting time.