Silica Sand an overview | ScienceDirect Topics
To make calcium silicate bricks, silica sand is mixed with high calcium lime at a sandlime ratio of 10 or 20. The mix is then compressed into moulds and "autoclaved" at about 170°C (340°F) for several hours. Some gel, similar to the calcium silicate hydrate gel of the type that is formed by cement, is formed, and this bonds the sand particles together.