High-strength wall ceramics based on phosphorus slag and bentonite clay

Introduction. One of the promising ways to get high-strength ceramics is the method of semi-dry pressing of the "coarsely dispersed component – finely ground binder" formula. This method suggests using crushed industrial waste as the core, and finely ground nanostructured fusible clay as the binder material. Methods and materials. In the research, bentonite clay of the Darbazinsky deposit of the Turkestan region was used as plastic material, and dense crystallized phosphorus slag which is a waste of phosphorus production was used as a non-plastic coarse material. The study of the prescription factors’ influence on the basic physical and mechanical properties of ceramic wall materials was carried out by the simplex method characterized as lattice planning of experiments. The nanostructure of the phosphorus slag and bentonite clay formula was studied by the electron microscopic analysis method. Results. The binder content in the amount of 25% guarantees the density of the packages, while the sintering effect becomes sufficient and the strength of the samples is 27.1 MPa. If the amount of binder increases from 25% to 40%, the sintering effect continues to grow and the strength of the samples reaches 54.3 MPa. Discussion. The results show that the most active sintering effect and the dense structures forming in coarse-grained formulas with high-calcium phosphorus slag occur at 40–60% binder content. The presence of flux around slag grains in an amount of less than 30% contributes to obtaining less dense samples, with a binder content of 40%, a density increase is observed, which corresponds to the mixed ceramic structures modeling. Conclusion. To get high-strength ceramic bricks, the content of coarsely dispersed components in the form of phosphorus slag with a fraction of less than 1.25 mm should amount to 60–70%, finely ground phosphorus slag should be 5–10%, and bentonite clay is to be 20–30%. Optimum technological indicators are: calcination temperature 1050–1100oC, pressing pressure 20–25 MPa, press powder moisture content 7–8%.