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ASR can lead to serious cracking in concrete, resulting in critical structural problems that can even force the demolition of a particular structure. [4] [5] [6] The expansion of concrete through reaction between cement and aggregates was first studied by Thomas E. Stanton in California during the 1930s with his founding publication in 1940. [7]
When atmospheric carbon dioxide (CO 2), or carbonate ions (HCO − 3, CO 2− 3 dissolved in water) diffuse into concrete from its external surface, they react with calcium hydroxide (portlandite, Ca(OH) 2) and the pH of the concrete pore water progressively decreases from 13.5 – 12.5 to 8.5 (pH of water in equilibrium with calcite).
Natural pozzolana (volcanic ash) deposits situated in Southern California in the United States. Pozzolans are a broad class of siliceous and aluminous materials which, in themselves, possess little or no cementitious value but which will, in finely divided form and in the presence of water, react chemically with calcium hydroxide (Ca(OH) 2) at ordinary temperature to form compounds possessing ...
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
Silicate carbonate minerals can be formed in limestone metamorphosed by heating from igneous intrusions. [1] Scawtite forms where the activity of calcium is high compared to H +. Spurrite forms in a limited range of calcium activity and high silica activity. [2] In magma, a carbonate rich melt is imiscible with a silicate melt. [3]
When treated with calcium oxides and water, silicate minerals form Portland cement. Equilibria involving hydrolysis of silicate minerals are difficult to study. The chief challenge is the very low solubility of SiO 4 4-and its various protonated forms. Such equilibria are relevant to the processes occurring on geological time scales.
A carbonate is a salt of carbonic acid, (H 2 CO 3), [2] characterized by the presence of the carbonate ion, a polyatomic ion with the formula CO 2− 3. The word "carbonate" may also refer to a carbonate ester , an organic compound containing the carbonate group O=C(−O−) 2 .
This figure describes the geological aspects and processes of the carbonate silicate cycle, within the long-term carbon cycle. The carbonate–silicate geochemical cycle, also known as the inorganic carbon cycle, describes the long-term transformation of silicate rocks to carbonate rocks by weathering and sedimentation, and the transformation of carbonate rocks back into silicate rocks by ...