THE INFLUENCE OF FORCED CARBONIZATION ON THE PROPERTIES OF GYPSUM-LIME SYSTEMS BASED ON SECONDARY RAW MATERIALS
The use of secondary raw materials for the production of building materials is a modern trend in solving environmental problems. In the Republic of Crimea, dumps of secondary raw materials – phosphogypsum and lime dust – have accumulated in large quantities at various enterprises. The analysis of phosphogypsum, which has been in the dumps for more than 5 years, showed that by its quality indicators it can be attributed to the 2nd grade in accordance with GOST 4013-2019, and the specific effective activity of the material (Aeff) corresponds to the I class of materials, which makes it suitable for the production of gypsum binders. Prototypes-cylinders were made from a mixture of phosphogypsum with lime dust of 1:1 composition at a pressure of 30 MPa and then subjected to hardening according to three schemes, in order to separate the passage of various types of hardening and study each of them for the physico-mechanical properties of the resulting material. The analysis of experimental data made it possible to establish the effectiveness of simultaneous flow in the system of two types of hardening – carbonate and hydration for lime and phosphogypsum components of the raw mixture, respectively. As a result of the organization of a mixed type of hardening of gypsum-lime binder, samples with a compressive strength of 26.5 MPa and a softening coefficient of 0.63 were obtained within 90 minutes. The calcium carbonate formed in the process, which is the product of the reaction between calcium hydroxide and carbon dioxide, significantly increases the water resistance of the hydration products of gypsum binder. It is established that with an optimal combination of technological factors and hardening conditions, a significant increase in the physical and mechanical characteristics of the carbonized material is possible in a short time.