Further understanding of the sensitivity of triethanolamine on the hydration and setting performance of cement: Effect of aging

After exposing cement under controlled relative humidity (RH) for different periods, impact of triethanolamine (TEA) on hydration and setting performance of aged cement was evaluated by Vicat test, calorimetry, XRD, and TGA. It is found anhydrite and hemihydrate can already transform to gypsum under 30 % RH, which leads to slight retardation on cement hydration. TEA accelerates the dissolution of sulfate carriers and eliminates the difference in hydration induced by sulfate carriers' alteration at 30 % RH. The further increased RH and time of aging led to increased surface coverage by hydration product and sulfate ions, which limited the accelerating effect of TEA on the dissolution of C3A, but not C4AF. TEA retards the hydration of mixture of C3A and sulfate carriers, which could be caused by the promoted dissolution of sulfate carriers by TEA. The formed nano-sized hydration products during aging could act as seeds and then accelerate the setting.