How the delayed addition of triethanolamine affects the performance of cement paste: competitive interaction of triethanolamine with sulfate ions

In order to reach the balance of the printability and buildability for concrete 3D printing, the combined effect of the addition time of triethanolamine (TEA) and the types of sulfate carriers on cement hydration and setting performance were investigated. It is found that, when hemihydrate (HH) or anhydrite (AH) is used as the only sulfate source in the artificial cement (ArC), the different addition methods of TEA, either simultaneous addition (S-method) with water or delayed addition (D-method) after the mixing of cement with water, do not change the setting time of the cement paste. However, when both anhydrite (AH) and hemihydrate (HH) are used as the sulfate source, a flash-setting phenomenon was observed for ArC prepared with the S-method but not the D-method. Further analysis indicates that the setting performance can be adjusted through the different combinations of TEA addition time and sulfate carriers, which could originate from the competitive interaction of sulfate ions released from sulfate carriers and TEA with the aluminate phase contained in the clinker.