Calcium silicate hydrate is produced by reaction of C3S or C2S with water. It is frequently described as a gel rather than a crystalline material because no consistent structure is discernible using X-ray diffraction.

BASIC USE – A calcium silicate building stone unit used in full-bed masonry veneer construction for both interior and exterior applications. They are pressure-formed and autoclave cured; resulting in high-density, severe weathering modular building stone units, with one or more finished faces.

Calcium-silicate hydrate (C-S-H) is the main binder in cement and concrete. It starts forming from the early stages of cement hydration and it progressively densifies as cement sets.

Calcium silicate (sand lime and flint lime) bricks are manufactured by mixing lime, sand and/or crushed silicaceous or flint stone together, with enough water to allow the mixture to be moulded under high pressure. They also have no ‘fireskin’ as would be seen with a clay brick.

ASTM C90 contains minimum requirements that assure properties necessary for quality performance, including specified constituent materials, minimum face shell and web thicknesses, minimum compressive strength, permissible variations in dimensions, and finish and appearance criteria.

New C-S-H gel could be produced into the concrete porous system as consequence of reaction between silanol groups from silica-based products and Ca2+ ions from portlandite, one of the main resultant products of cement hydration.

Inert pigments may be included to influence the final brick colour. The units are shaped into moulds under pressure and cured by autoclaving at around 170°C for between 4 and 16 hours. During curing some of the lime reacts with the siliceous aggregate to form calcium silicate hydrate, which binds the brick together.

Calcium silicate units are manufactured from fine siliceous aggregate (and sometimes silica flour) and 10–20% ground quicklime or well hydrated lime. Inert pigments may be included to influence the final brick colour. The units are shaped into moulds under pressure and cured by autoclaving at around 170°C for between 4 and 16 hours.

Gross area compressive strength is still used for empirically designed masonry (IBC Section 2109). Maximum permissible water absorption is shown in Table 3. Absorption is a measure of the total water required to fill all voids within the net volume of concrete.

These requirements include items such specified component materials, compressive strength, permissible variations in dimensions, and finish and appearance criteria. Currently, seven ASTM standards apply to units intended primarily for construction of concrete masonry walls, beams, columns or specialty applications (see Table 1).