Acceleration of cement hydration – A review of the working mechanisms, effects on setting time, and compressive strength development of accelerating admixtures

The desire to accelerate cement hydration for faster construction processes is almost as old as cement itself. In recent years, however, new requirements for the acceleration, and the precise control of the setting behavior and the early strength development of cementitious materials have emerged. This is due to the increasing proportion of cements with reduced clinker content and new technologies, such as additive manufacturing. As the use of accelerating admixtures offers high flexibility in controlling of early cement hydration, these admixtures might play a key role in developing fast-hydrating green cements and cementitious materials suitable for application in additive manufacturing. A detailed understanding of the mechanisms by which different accelerating admixtures influence cement hydration and their influence on setting and hardening is thus required. In this study, the most widely used accelerators for cast and sprayed concrete are reviewed, focusing on their influence on the aluminate and silicate reaction of cement hydration as well as the setting and hardening depending on the dosage of the admixture.