Influence of water saturation on strength of modified gypsum-alumina expanding cement at stage of delayed hardening

The article analyzes the influence of material composition of modified gypsum-alumina expanding cement with regard to mineral components ratio on its mechanical-and-physical properties change due to water saturation at the stage of delayed hardening. The expandable cementing medium applied in the survey, except for traditional components such as crushed gypsum rock and alumina cement, contained additionally portland cement and superplasticizer, based on polycarboxylic ethers. It has been established that depending on mineral components ratio water saturation of one-year-old cement rock can either improve or worsen its strength properties, provided that bending and compression resistance can change asynchronously and divergently. A regularity has been revealed regarding composite water resistance change depending on mass ratio of portland cement and gypsum rock (AC/GR). Within the variability of experimental factors a judicious ratio - AC/GR=0,2-0,95 has been established, where bending and compression resistance does not decrease as a result of cement rock water saturation during 48 hours. (paper)