Preparation and hydration mechanism of aluminum formate/aluminum sulfate based alkali-free composite accelerator for sprayed concrete

Abstract The high alkali content of alkaline accelerators has a negative influence on the late strength and durability concrete. Further, their corrosive nature is harmful to skin construction personnel, posing safety concerns. Therefore, development alkali-free gained interest, especially in shotcrete-based constructions. production process aluminum-sulfate-based simple less exothermic, with no impact later concrete, aspects that are widely recognized very important construction. However, sulfate may have significant concrete; therefore, reducing plays an role enhancing In this study, liquid accelerator was synthesized by replacing aluminum formate, which effectively reduced content. Experiments were performed concrete samples replaced formate at different levels. results showed 3CaO·Al 2 O 3 (C A) prepared from form calcium aluminate, similar ettringite phase. promoted dissolution Ca SiO 5 S), thus accelerating hydration Meanwhile, ions hydrolyzed also participated reaction, resulting dual participation cations anions hydration, leading synergistic effect sulfate.