In the presence of water ( during a rainstorm, for instance ) unreacted cement particles recently exposed due to cracking hydrate and form a number of products ( Calcium Silicate Hydrate, calcite, etc . ) that expand and fill in the crack.
22.
During this steam pressure hardening process, when the temperature reaches 190?Celsius ( 374?Fahrenheit ) and the pressure reaches 8 to 12 bar, quartz sand reacts with calcium hydroxide to form calcium silicate hydrate, which gives AAC its high strength and other unique properties.
23.
Serpentine is stable at high pH in the presence of brucite like calcium silicate hydrate, ( C-S-H ) phases formed along with portlandite ( Ca ( OH ) 2 ) in hardened Portland cement paste after the hydration of belite ( Ca 2 SiO 4 ), the artificial calcium equivalent of forsterite.
24.
From the digging of ancient Roman ruins, one knows that approximately 95 % of the concretes and mortars constituting the Roman buildings consist of a very simple lime cement, which hardened slowly through the precipitating action of carbon dioxide CO 2, from the atmosphere and formation of calcium silicate hydrate ( C-S-H ).
