Effect of MgSiF ₆ on the properties of sulfoaluminate cementitious grouting materials in the presence of triethanolamine

Magnesium silicofluoride (MgSiF6), a byproduct of phosphate fertilizer production, serves as an effective retarder of sulfoaluminate cementitious grouting materials (SAGMs). The incorporation of triethanolamine (TEA) at concentrations ranging from 0.15 to 0.85 g/L results in a reduction of the slurry’s setting time and an increase in its compressive strength. Conversely, when the concentration is increased to 1.5–8.5 g/L, a decline in compressive strength is observed. The underlying mechanism for this phenomenon requires further investigation. The results show that when the concentration of MgSiF 6 is 1.5 g/L, a TEA concentration of 0.15–8.5 g/L promotes the dissolution of CaSO 4 and C 4 A 3 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mover accent="true"> <mml:mi mathvariant="normal">S</mml:mi> <mml:mo>¯</mml:mo> </mml:mover> </mml:mrow> </mml:math> . The promoting effect on the dissolution of CaSO 4 increases with the increase in TEA concentration, while the promoting effect on the dissolution of C 4 A 3 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mover accent="true"> <mml:mi mathvariant="normal">S</mml:mi> <mml:mo>¯</mml:mo> </mml:mover> </mml:mrow> </mml:math> initially shows an increasing trend and then decreases. In the presence of MgSiF 6 , TEA promoted the formation of ettringite at low concentrations (0.15 and 0.85 g/L) and inhibiting its formation at high concentrations (1.5 and 8.5 g/L). All concentrations of TEA encourage the formation of aluminum hydroxide, but at 0.85 g/L concentration, the size of the ettringite and aluminum hydroxide generated is smaller, affecting the pore structure and resulting in higher compressive strength.