Accelerating strength development of cementitious mixtures using aluminum sulfate liquid accelerator with aluminium formate

The alkali-free liquid accelerator (ALSF) was prepared with aluminum sulfate and aluminum formate as the main components. The effects of ALSF on the setting of paste and the mechanical strength of mortar were studied, and the impact of ALSF on the early hydration behavior and hydration products of paste were investigated by isothermal calorimeter analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermogravimetric (TG) analysis. The results show that ALSF is excellent for the rapid setting and hardening of the cement. When the content of ALSF was 8 wt%, the initial setting time and final setting time of paste were 85 s and 180 s, respectively, and the 1 d and 28 d strengths of mortar were 9.52 MPa and 44.42 MPa, respectively. ALSF can accelerate the dissolution and hydration of C3A and C3S and promote the formation of 3CaO center dot Al2O3 center dot 3CaSO4 center dot 32H2O (ettringite), AFt formate, and portlandite.