Utilization of tartaric acid and 5-sulfosalicylic acid for tailoring the performance of aluminum sulfate alkali-free accelerator

The organic components used in the alkali-free accelerator have a significant influence on the performance of the accelerator. The effects of two distinct types of organic acids, tartaric acid (TA) and 5-sulfosalicylic acid (SSA), on the performance of alkali-free accelerator, mainly on the setting time of cement paste and the early strength of mortar were investigated in this work. The mechanism of effects was studied by the isothermal calorimetry, SEM, XRD, and FT-IR analysis. The results demonstrate that both TA and SSA can extend the setting of cement; TA can diminish the early strength of mortar, while SSA has little influence. The –COOH in TA can be complexed with Ca2+ to form calcium tartrate, which accelerates the dissolution of gypsum and hydration of C3A; The calcium tartrate and R-OH in TA can be adsorbed on the surface of C3S, prolonging the induction period and inhibiting the hydration of C3S. The Ar-OH in SSA can react with Al3+ to form a stable chelate, inhibit the hydration of C3A and extend the setting of cement. The Ar-OH adsorbed on the surface of C3S can also prolong the induction period, but the Ar-OH is more active than R-OH, resulting in unstable adsorption reaction and poor effect on extending the induction period.