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The alkali–silica reaction (ASR), also commonly known as concrete cancer, [3] is a deleterious internal swelling reaction that occurs over time in concrete between the highly alkaline cement paste and the reactive amorphous (i.e., non-crystalline) silica found in many common aggregates, given sufficient moisture.
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. [ 12 ] [ 13 ] This is where carbon dioxide enriched rain or seepage water forms a weak carbonic acid , which leaches calcium carbonate (CaCO 3 ) from within the ...
It is a white, caustic, alkaline, crystalline solid at room temperature. The broadly used term lime connotes calcium-containing inorganic compounds, in which carbonates, oxides, and hydroxides of calcium, silicon, magnesium, aluminium, and iron predominate. By contrast, quicklime specifically applies to the single compound calcium oxide.
There is often confusion between the meanings of the terms 'geopolymer cement' and 'geopolymer concrete'. A cement is a binder, whereas concrete is the composite material resulting from the mixing and hardening of cement with water (or an alkaline solution in the case of geopolymer cement), and stone aggregates.
Concrete is the most widely used material in existence and is behind only water as the planet's most-consumed resource. [ 2 ] Cements used in construction are usually inorganic , often lime - or calcium silicate -based, and are either hydraulic or less commonly non-hydraulic , depending on the ability of the cement to set in the presence of ...
A fairly well-defined reaction front can often be observed in thin sections; ahead of the front the concrete is normal, or near normal. Behind the reaction front, the composition and the microstructure of concrete are modified. These changes may vary in type or severity but commonly include: Extensive cracking; Expansion
Concrete is a composite material composed of aggregate bonded together with a fluid cement that cures to a solid over time. Concrete is the second-most-used substance in the world after water, [1] and is the most widely used building material. [2] Its usage worldwide, ton for ton, is twice that of steel, wood, plastics, and aluminium combined. [3]
Weathering carbonation occurs in concrete when calcium compounds react with carbon dioxide from the atmosphere and water in the concrete pores. The reaction is as follows. First, through chemical weathering, CO 2 reacts with water in the concrete pores to form carbonic acid: