Improving the mechanical performance of high-grade slag cement by the addition of Portland cement and sulfoaluminate cement

This paper investigates the development of a ternary cement with properties that result in a synergy between its various components (slag cement, Portland cement and cement sulfoaluminate). The results of compressive strength testing on standard mortar (complying with European Standard NF EN 196-1) indicate that it is necessary to use Portland cement and calcium sulfoaluminate cement together to accelerate the acquisition of strength of high-grade slag cement. To explain this, certain analyses were carried out: XRD and DTA–TGA on pure paste, and mercury porosimetry and semi-adiabatic calorimetry on mortar. The investigation showed that slag activation and hydration are dependent on the composition of the binder and that its variation can lead to different microstructure outcomes and the formation of different hydrates.

► Acceleration is due to ettringite from hydration of yeelimite and gypsum.
► Activation of yeelimite by portlandite depends on gypsum ratio in CSA.
► Medium term strength is due to sulfo-calciq slag activation.
► Increased quantity of hydrates or change of morphology of hydrates.