The present invention is based on solid-state reaction or reactions in the presence of small amounts of water, between phospho gypsum and agglutinating-neutralizing agents, principally though the application of oxy and hydroxy compounds, without discounting use of the respective carbonates of magnesium, aluminum and principally calcium, in addition to mixtures of these, and the subsequent preparation of self-hardening pellets which facilitate transport and handling. The technological process associated with the invention notably simplifies both the number and type of individual operations, and the preparation of pellets from mixtures of phosphor gypsum; it also reduces energy costs by operating at low temperatures (150.degree.C.) during short periods (1-2 hours), while reducing the quantity of neutralizing agents, and minimizing the volume of water required for the process.