Material cycle realization by hazardous phosphogypsum waste, ferrous slag, and lime production waste application to produce sustainable construction materials

The article presents data from new compositions of construction materials developed from three types of Kazakhstan enterprises' industrial waste-highly alkaline (pH = 13.5) hazardous sludge of phosphogypsum (PG) waste from Karatau deposits (52-78 wt.%), ground-cooled converter slag (CS) from Karaganda Metallurgical Plant (20-45%), and lime production waste (LPW) from a small plant near Astana (2%). This research aimed to develop new compositions of materials, which correspond to Kazakhstan's mechanical and environmental standards, to study the processes of new composites' structure formation in the process of their hydration and resistance strengthening. The axial compressive-resistance values of the developed composites reached 5.3-6.8-9.6 and 14.9 MPa after 3, 7, 14, and 550 days of hydration, respectively; the values of the coefficient of linear expansion were in the range of 0.23 and 3.14%, and those of water absorption between 8.2 and 18.4%. The formation processes of the materials' structure were studied by the XRD, SEM, EDS, AAS, and LAMMA methods. The analyses of the solubility and leaching of metals by the AAS method showed the compliance of the new compositions with Kazakhstan's sanitary standards.