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Calcium-silicate passive fire protection board being clad around steel structure in order to achieve a fire-resistance rating. Calcium silicate is commonly used as a safe alternative to asbestos for high-temperature insulation materials. Industrial-grade piping and equipment insulation is often fabricated from calcium silicate.
Cement hydration and strength development mainly depend on two silicate phases: tricalcium silicate (C 3 S) , and dicalcium silicate (C 2 S) . [1] Upon hydration, the main reaction products are calcium silicate hydrates (C-S-H) and calcium hydroxide Ca(OH) 2, written as CH in the cement chemist notation. C-S-H is the phase playing the role of ...
The sight of calthemite is a visual sign that calcium is being leached from the concrete structure and the concrete is gradually degrading. [12] [17] In very old concrete where the calcium hydroxide has been leached from the leachate seepage path, the chemistry may revert to that similar to "speleothem" chemistry in limestone cave.
Only calcium silicates contribute to the strength. Tricalcium silicate is responsible for most of the early strength (first 7 days). [3] Dicalcium silicate, which reacts more slowly, only contributes to late strength. Calcium silicate hydrate (also shown as C-S-H) is a result of the reaction between the silicate phases of Portland cement and water.
The main phases are the calcium silicate hydrates (C-S-H) (the "glue" in cement paste), calcium sulfo-aluminate phases (AFm and AFt, ettringite) and hydrogarnet. C-S-H phases are less soluble (~ 10 −5 M) than portlandite (CH) (~ 2.2 10 −2 M at 25 °C) and therefore are expected to play a negligible role for the calcium ions release.
Creep and shrinkage of concrete are two physical properties of concrete.The creep of concrete, which originates from the calcium silicate hydrates (C-S-H) in the hardened Portland cement paste (which is the binder of mineral aggregates), is fundamentally different from the creep of metals and polymers.
Thaumasite is a calcium silicate mineral, containing Si atoms in unusual octahedral configuration, with chemical formula Ca 3 Si(OH) 6 (C O 3)(SO 4)·12H 2 O, also sometimes more simply written as CaSiO 3 ·CaCO 3 ·CaSO 4 ·15H 2 O. It occurs as colorless to white prismatic hexagonal crystals, typically as acicular radiating groups. It also ...
The hydrate is referred to as the calcium silicate hydrate – "C-S-H-" – phase. It grows as a mass of interlocking needles that provide the strength of the hydrated cement system. High alite reactivity is desirable in Portland cement manufacture, and this is achieved by retaining, as far as possible, high temperature polymorphs, in crystals ...