The aforementioned alite and belite are forms of the purer compounds known as tricalcium silicate and dicalcium silicate, respectively. They are named according to their chemical makeup. Tricalcium silicate is otherwise written as (CaO)3SiO2 and dicalcium silicate as (CaO)2SiO2. When water is added to these compounds, one of the main products of the reaction is calcium silicate hydrate. Calcium silicate hydrate creates multitudes of tiny fibers when it is formed within the hydraulic cement. These fibers are what toughen the cement overall and make it impervious to water.