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:''For less common types of alkali-driven concrete degradation see alkali-aggregate reaction (disambiguation page)''. The alkali–silica reaction (ASR) is a reaction which occurs over time in concrete between the highly alkaline cement paste and reactive non-crystalline (amorphous) silica, which is found in many common aggregates and sufficient moisture. This reaction causes the expansion of the altered aggregate by the formation of a swelling gel of calcium silicate hydrate (C-S-H). This gel increases in volume with water, and exerts an expansive pressure inside the material, causing spalling and loss of strength of the concrete, finally leading to its failure. ASR can cause serious cracking in concrete, resulting in critical structural problems that can even force the demolition of a particular structure. ==Chemistry== ASR is the same as the pozzolanic reaction, which is a simple acid-base reaction between calcium hydroxide, also known as Portlandite, or (Ca(OH)2), and silicic acid (H4SiO4, or Si(OH)4). For the sake of simplicity, this reaction can be schematically represented as following: :Ca(OH)2 + H4SiO4 → Ca2+ + H2SiO42− + 2 H2O → CaH2SiO4 · 2 H2O 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Alkali–silica reaction」の詳細全文を読む スポンサード リンク
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