Alkali-free setting accelerator for hydraulic binders

For the acceleration of the setting and of the hardening of a hydraulic binding agent such as cement, limestone, hydraulic limestone and gypsum as well as mortar and concrete prepared thereof, are added to the mixture, which contains said binding agent, from 0.5 to 10 percent by weight, referred to the weight of this binding agent, of an alkali-free setting- and hardening-accelerator, whereby this accelerator contains aluminum hydroxide.