Influence of different alkali phosphates on the workability and hydration of magnesium silicate cements

Abstract

This study evaluates alternative alkali phosphates as additives for magnesium silicate cements to improve workability and hydration behavior. Sodium hexametaphosphate (SHMP) has been extensively investigated, whereas sodium tripolyphosphate (STPP) and tetrapotassium pyrophosphate (TKPP) are introduced here as new additives in this context. By complexing Mg ²⁺ and modifying the particle surface charge, the alkali phosphates increase electrostatic repulsion between particles, and thereby enhance workability. By suppressing early brucite formation and enhancing pH value, the M‐S‐H formation is increased. Preliminary results indicate that TKPP represents a promising alternative to the established alkali phosphate additive SHMP.