Forecasting Strength Parameters of Hardened Geopolymer Slurries Applied to Seal Casing Columns in Boreholes

Abstract

Ensuring effective sealing of casing columns in boreholes requires the use of the appropriate technology of cement slurry injection into the annular space and the use of a properly designed cement slurry recipe. Very often, when selecting the technological parameters of the cement slurry, special attention is paid to the technological parameters of the fresh cement slurry, but little attention is paid to the mechanical parameters of the cement sheath that is being formed (the cement slurry after setting). In order to improve the parameters of the hardened cement slurry in the annular space, the cement slurry of a new generation with increased durability (so-called geopolymers) is used. Slurries based on geopolymers are obtained by modifying slurries based on common-use cements with mineral additives with pozzolanic or hydraulic properties. Most often, these additives are fly ashes from the combustion of hard coal or ground granulated blast furnace slags. The article presents the results of testing the mechanical parameters of hardened cement slurries prepared on the basis of CEM V multi-component cement. It was found that the increase in the amount of silica fly ash in the slurry causes a delay in the strength growth rate; such slurries have lower values of early strength. The water–cement coefficient has the strongest influence on the mechanical parameters. The test results are also statistically developed, thanks to which it is possible to select the appropriate mathematical model, and this enables the prediction of mechanical parameters for slurries as a function of their hardening time. Such a mathematical solution can save some labor-intensive research, which, however, cannot be omitted in the final stage of slurry design.