Editing Cement (section)

==Setting, hardening and curing==
Cement starts to set when mixed with water, which causes a series of hydration chemical reactions. The constituents slowly hydrate and the mineral hydrates solidify and harden. The interlocking of the hydrates gives cement its strength. Contrary to popular belief, hydraulic cement does not set by drying out — proper curing requires maintaining the appropriate moisture content necessary for the hydration reactions during the setting and the hardening processes. If hydraulic cements dry out during the curing phase, the resulting product can be insufficiently hydrated and significantly weakened. A minimum temperature of 5&nbsp;°C is recommended, and no more than 30&nbsp;°C.<ref>{{Cite web|url=https://www.sovchem.co.uk/profile/news/read/id/206/|title=Using cement based products during winter months|date=29 May 2018|website=sovchem.co.uk|archive-url=https://web.archive.org/web/20180529203647/https://www.sovchem.co.uk/profile/news/read/id/206/|archive-date=29 May 2018|url-status=dead}}</ref> The concrete at young age must be protected against water evaporation due to direct insolation, elevated temperature, low [[relative humidity]] and wind.

The ''interfacial transition zone'' (ITZ) is a region of the cement paste around the [[Aggregate (composite)|aggregate]] particles in [[concrete]]. In the zone, a gradual transition in the [[Microstructure|microstructural]] features occurs.<ref name="scr01" /> This zone can be up to 35 micrometer wide.{{r|ty01|p=351}} Other studies have shown that the width can be up to 50 micrometer. The average content of unreacted clinker phase decreases and [[porosity]] decreases towards the aggregate surface. Similarly, the content of [[ettringite]] increases in ITZ. {{r|ty01|p=352}}