In the manufacture of calcium silicate bricks (lime-sand bricks), the lime, sand and water mixture is pre-formed in presses. These bricks are hardened in autoclaves under steam pressure at temperatures between 160 and 203°C. Lime and quartz sand react to form compounds that give calcium silicate bricks their compressive strength.

A calcium silicate brick is characterised by its good sound-insulating properties and its high compressive strength.

As well as its wide range of quicklimes, Lhoist also produces a special quality of lime for the manufacturers of calcium silicate bricks. This lime contains special elements such as silica, aluminium and iron, that act as hydraulic components, improving the "green" strength of the bricks.