It is a mineral considered to be specifically an aluminosulfonato of calcium (with aluminium and calcium sulfate), which moisturize foma cement. It also means born or resident in the city of Ettringen in Rhineland, Germany. Etringenita.
Ettringite: Sulphate calcium aluminate hydrated which crystallizes in the trigonal system.
The entringita is a complex salt that forms in cement when gypsum is added to the mixture to regulate the setting time, the entringita during this process is not harmful and is called primary entringita. If this is produces in other phases of the process can be damaging since has a high power expansive and can do that is shed pieces when is dry.