Abstract: Concrete hardening accelerator is a kind of admixture which can accelerate the early strength development of concrete.It's very important for speeding up the construction schedule and improving velocity of engineering operations.Its content is generally not more than 5% of the mass of cement.Hardening accelerator is divided into inorganic,organic,composite hardening accelerators,and the component and dosage of each one are induced.In order to provide theoretical foundation for the development and combination of hardening accelerators,the mechanism of different hardening accelerators is summarized,which can explain how to improve the hydration reaction speed of the cement,and accelerate the setting and hardening of cement paste by the hardening accelerator in theory.Further,the current problems are concluded through analyzing the application properties of hardening accelerators,and the development direction is pointed out.Especially,the hardening accelerator with low concentration and low cement-sand ratio cementitious system should be emphasized.

Key words: Inorganic hardening accelerators, Organic hardening accelerators, Composite hardening accelerators, Mechanism,Application property