Free-of-Cement Sulfate-Slag Binder with Increased Phosphoanhydrite Content

For the sustainable development of mankind, a necessary condition is the reduction of the volume of CO₂ emissions, a significant share of which is created by the production of Portland cement. In this regard, the development of alternative products is relevant, one of which, experiencing its rebirth at a new stage of development, is sulfate-slag binder. The article considers the issues of obtaining its cement-free variety with an excess content of phosphoanhydrite, which acts as a sulfate activator of slag hardening. The possibility of obtaining water-resistant free-of-cement excess-sulfate-slag binders with a compressive strength of hardened stone up to 50 MPa has been established. The features of the structure formation processes and the nature of new formations of free-of-cement excess-sulfate-slag binders with a phosphoanhydrite content of 40% have been revealed. Based on the combination of properties, the developed binder can become an effective replacement for Portland cement when solving the problems of obtaining large volumes of concrete of medium strength classes with low heat generation and high sulfate resistance, in cases where it is possible to ensure a favorable temperature and humidity regime for 28–90 days. Cement-free excess-sulfate-slag binders have prospects for further development, their production and application will entail a significant positive environmental and economic effect, which will consist of the possibility of recycling phosphogypsum into a commercial product with high added value, reducing CO₂ emissions into the environment, and freeing up territories occupied by waste storage.