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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 ...
Degrading concrete has been the focus of many studies and the most obvious sign is calcium-rich leachate seeping from a concrete structure. [5] [6] [7]Calthemite stalactites can form on concrete structures and "artificial caves" lined with concrete (e.g. mines and tunnels) significantly faster than those in limestone, marble or dolomite caves.
Alkali–silica reaction. Characteristic crack pattern associated with the alkali–silica reaction affecting a concrete step barrier on a US motorway. Note the typical fatty aspect of the silicagel exudations imbibing the concrete surface along the two sides of the cracks. [1][2] The alkali–silica reaction (ASR), also commonly known as ...
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 ...
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.
Caliche forms where annual precipitation is less than 65 centimeters (26 in) per year and the mean annual temperature exceeds 5 °C (41 °F). Higher rainfall leaches excess calcium completely from the soil, while in very arid climates, rainfall is inadequate to leach calcium at all and only thin surface layers of calcite are formed.
The water–cement ratio (w/c ratio, or water-to-cement ratio, sometimes also called the Water-Cement Factor, f) is the ratio of the mass of water (w) to the mass of cement (c) used in a concrete mix: The typical values of this ratio f = w⁄c are generally comprised in the interval 0.40 and 0.60. The water-cement ratio of the fresh concrete ...
Leaching is the process of a solute becoming detached or extracted from its carrier substance by way of a solvent. [ 1 ] 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 ...