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To attempt to simplify and to stylize a very complex set of various reactions, the whole ASR reaction, after its complete evolution (ageing process) in the presence of sufficient Ca 2+ cations available in solution, could be compared to the pozzolanic reaction which would be catalysed by the undesirable presence of excessive concentrations of alkali hydroxides (NaOH and KOH) in the concrete.
Concrete hardens as a result of the chemical reaction between cement and water (known as hydration and producing heat). For every mass (kilogram, pound, or any unit of weight) of cement (c), about 0.35 mass of water (w) is needed to fully complete the hydration reactions. [1]
When water is added to cement, each of the compounds undergoes hydration and contributes to the final state of the concrete. [2] 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.
The pozzolanic reaction is the chemical reaction that occurs in portland cement upon the addition of pozzolans. It is the main reaction involved in the Roman concrete invented in Ancient Rome and used to build, for example, the Pantheon. The pozzolanic reaction converts a silica-rich precursor with no cementing properties, to a calcium silicate ...
Hydraulic cements (e.g., Portland cement) set and become adhesive through a chemical reaction between the dry ingredients and water. The chemical reaction results in mineral hydrates that are not very water-soluble. This allows setting in wet conditions or under water and further protects the hardened material from chemical attack.
Instead of using a 'nominal mix' of 1 part cement, 2 parts sand, and 4 parts aggregate, a civil engineer will custom-design a concrete mix to exactly meet the requirements of the site and conditions, setting material ratios and often designing an admixture package to fine-tune the properties or increase the performance envelope of the mix ...
The phase composition of a particular cement can be quantified through a complex set of calculation known as the Bogue formula. To avoid the flash setting of concrete, due to the very fast hydration of the tricalcium aluminate (C 3 A), 2–5 wt. % calcium sulfate is interground with the cement clinker to prepare the cement powder.
Alkali–aggregate reaction is a term mainly referring to a reaction which occurs over time in concrete between the highly alkaline cement paste and non-crystalline silicon dioxide, which is found in many common aggregates. This reaction can cause the expansion of the altered aggregate, leading to spalling and loss of strength of concrete.