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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.
Lime re-absorbs the carbon dioxide (CO 2) emitted by its calcination (firing in a kiln), thus partially offsetting the large amount emitted during its manufacture. The more hydraulic a lime, the less CO 2 is reabsorbed during set, for example, 50% of CO 2 is reabsorbed by NHL 3.5 during the set, compared to 100% of CO 2 being reabsorbed by pure ...
Other polymers, such as polyethylene and polystyrene, do not normally absorb much moisture, but are able to carry significant moisture on their surface when exposed to liquid water. [ 33 ] Type-6 nylon (a polyamide ) can absorb up to 9.5% of its weight in moisture.
Chalk is a soft, white, porous, sedimentary carbonate rock.It is a form of limestone composed of the mineral calcite and originally formed deep under the sea by the compression of microscopic plankton that had settled to the sea floor.
Crystal structure of calcite. Calcium carbonate is a chemical compound with the chemical formula Ca CO 3.It is a common substance found in rocks as the minerals calcite and aragonite, most notably in chalk and limestone, eggshells, gastropod shells, shellfish skeletons and pearls.
It does not absorb water as it consists of closed cells. Resists fire. Used in Europe. Most plant based insulations such as wood chips, wood fiber, sawdust, redwood bark, hemlock fiber, balsa wood, hemp fiber, flax fiber, etc. are hygroscopic. Wood absorbs water, which reduces its effectiveness as a thermal insulator.
The milkiness disappears since calcium bicarbonate is water-soluble. Calcium hydroxide reacts with aluminium. This reaction is the basis of aerated concrete. [8] It does not corrode iron and steel, owing to passivation of their surface. Calcium hydroxide reacts with hydrochloric acid to give calcium hydroxychloride and then calcium chloride.
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