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Chlorides, particularly calcium chloride, have been used to shorten the setting time of concrete. [5] However, calcium chloride and (to a lesser extent) sodium chloride have been shown to leach calcium hydroxide and cause chemical changes in Portland cement, leading to loss of strength, [6] as well as attacking the steel reinforcement present ...
Sulfate attack in concrete and mortar. Cement hydration and strength development mainly depend on two silicate phases: tricalcium silicate (C 3 S) (alite), and dicalcium silicate (C 2 S) (belite). [ 1 ] Upon hydration, the main reaction products are calcium silicate hydrates (C-S-H) and calcium hydroxide Ca (OH) 2, written as CH in the cement ...
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.
It causes cracks to widen and deepen, quickly and efficiently takes root, and promotes calcium oxalate. By causing calcium oxalate, there is an increase in the speed of calcium ion leaching, which lowers the overall strength of concrete. In 90 days, exposure to the fungus resulted in a mass reduction of 7.2% in the concrete.
Calcium aluminates can form complex salts in combination with different types of anions.Two series of calcium aluminates are known in cement chemistry: AFm and AFt phases, being respectively mono- or tri-substituted with a given divalent anion X (e.g. SO 2− 4, CO 2− 3, or hosting a divalent impurity such as SeO 2− 4 [3]...), or with two units of a monovalent anion, e.g. OH −, Cl − ...
In chemistry, efflorescence (which roughly means "the flowering" in French) is the migration of a salt to the surface of a porous material, where it forms a coating. The essential process involves the dissolving of an internally held salt in water or occasionally, in another solvent. The water, with the salt now held in solution, migrates to ...
Leaching is a naturally occurring process which scientists have adapted for a variety of applications with a variety of methods. Specific extraction methods depend on the soluble characteristics relative to the sorbent material such as concentration, distribution, nature, and size. [ 1 ] Leaching can occur naturally seen from plant substances ...
Calthemite straw stalactite (right side) is bent due to direction of prevailing air movement during periods of its growth. Calthemite is a secondary deposit, derived from concrete, lime, mortar or other calcareous material outside the cave environment. [1][2] Calthemites grow on or under man-made structures and mimic the shapes and forms of ...