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During the curing period, concrete is ideally maintained at controlled temperature and humidity. To ensure full hydration during curing, concrete slabs are often sprayed with "curing compounds" that create a water-retaining film over the concrete. Typical films are made of wax or related hydrophobic compounds.
The addition of an accelerator speeds the setting time and thus curing starts earlier. [1] This allows concrete to be placed in winter with reduced risk of frost damage. [2] Concrete is damaged if it does not reach a strength of 500 pounds per square inch (3.4 MPa) before freezing. [3] Typical cement accelerators are calcium nitrate (Ca(NO 3)
These are created during concrete mixing (while the slurry is in its liquid state), with most surviving to remain part of it when hardened. Air entrainment makes concrete more workable [1] during placement, and increases its durability when hardened, particularly in climates subject to freeze-thaw cycles. [2] It also improves the workability of ...
Accelerated curing is any method by which high early age strength is achieved in concrete. These techniques are especially useful in the prefabrication industry, wherein high early age strength enables the removal of the formwork within 24 hours, thereby reducing the cycle time, resulting in cost-saving benefits. [ 1 ]
Depending on the climate, the curing process may take longer and require more frequent wetting. Once the concrete is cured, it sits for two to three weeks before the process is complete. [citation needed] When hydrophobic concrete is made through the use of an admixture, a powder with the hydrophobic chemicals is added during the batching process.
Concrete and metal planters are typically freeze-resistant and would be considered the most durable to be overwintered. “However, even these types of containers can experience surface damage ...
Conversely, concrete is one of the most powerful tools for proper flood control, by means of damming, diversion, and deflection of flood waters, mud flows, and the like. Light-colored concrete can reduce the urban heat island effect, due to its higher albedo. [3] However, original vegetation results in even greater benefit.
Concrete has a very low coefficient of thermal expansion, and as it matures concrete shrinks. All concrete structures will crack to some extent, due to shrinkage and tension. Concrete which is subjected to long-duration forces is prone to creep. The density of concrete varies, but is around 2,400 kilograms per cubic metre (150 lb/cu ft). [1]