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Calcium silicate, also known as slag, is produced when molten iron is made from iron ore, silicon dioxide and calcium carbonate in a blast furnace. When this material is processed into a highly refined, re-purposed calcium silicate aggregate, it is used in the remediation of acid mine drainage (AMD) on active and passive mine sites. [ 13 ]
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.
Calcium ions then react with the soluble sodium silicate gel to convert it into solid calcium silicate hydrates (C-S-H). The C-S-H forms a continuous poorly permeable coating at the external surface of the aggregate. The penetrated alkaline solution (NaOH / KOH) converts the remaining siliceous minerals into bulky soluble alkali silicate gel.
Ground granulated blast furnace slag is a latent hydraulic binder forming calcium silicate hydrates (C-S-H) after contact with water. It is a strength-enhancing compound improving the durability of concrete. It is a component of metallurgic cement (CEM III in the European norm EN 197).
But actual bioceramic aggregates are composed of pure medical graded calcium silicate based material. 4. Calcium aluminate bioceramic material - (alumina cement in minerals, calcium aluminate cements in bioceramics) Alumina is an initial fast setting element and high compressive strength.
Alkali–aggregate reaction – Expansive chemical reaction damaging concrete (AAR) Alkali–silica reaction – Chemical reaction damaging concrete (ASR) Caesarea Maritima – Ancient Levantine city; its ancient artificial bay was built with pozzolan; Calcium silicate hydrate – Main product of the hydration of Portland cement (C-S-H)
Loss of bond between the cement paste and aggregate; Alteration of hardened cement paste composition, with monosulfate aluminates phase converting to ettringite and, in later stages, gypsum formation. The necessary additional calcium is provided by the calcium hydroxide and calcium silicate hydrate in the cement paste
Geopolymer cement also has the ability to form a strong chemical bond with silicate rock-based aggregates. [ citation needed ] There is often confusion between the meanings of the terms 'geopolymer cement' and 'geopolymer concrete'.