Search results
Results from the WOW.Com Content Network
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 ...
When the cement paste is exposed to the air and meteoric water reacts with the atmospheric CO 2, portlandite and the calcium silicate hydrate (CSH) of the hardened cement paste become progressively carbonated and the high pH gradually decreases from 13.5 – 12.5 to 8.5, the pH of water in equilibrium with calcite (calcium carbonate) and the ...
The major raw material for the clinker-making is usually limestone mixed with a second material containing clay as a source of alumino-silicate. An impure limestone containing clay or silicon dioxide (SiO 2) can be used. The calcium carbonate (CaCO 3) content of these limestones can be as low as 80% by weight. During the calcination process ...
During this steam pressure hardening process, when the temperature reaches 190 °C (374 °F) and the pressure reaches 800 to 1,200 kPa (8.0 to 12.0 bar; 120 to 170 psi), quartz sand reacts with calcium hydroxide to form calcium silicate hydrate, which gives AAC its high strength and other unique properties.
Dicalcium silicate is stable, and is readily prepared from reactive CaO and SiO 2 at 300 °C. The low temperature form is γ-belite, or lime olivine . This form does not hydrate, and is avoided in cement manufacture.
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.
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.