Editing Concrete (section)

===Mass structures===
{{main|Mass concrete}}
[[File:UserKTrimble-AP Taum Sauk Reservoir UnderConstruction Nov 22 2009 crop1.jpg|thumb|Aerial photo of reconstruction at [[Taum Sauk Hydroelectric Power Station|Taum Sauk]] (Missouri) pumped storage facility in late November 2009. After the original reservoir failed, the new reservoir was made of roller-compacted concrete.]]

Due to cement's [[exothermic]] chemical reaction while setting up, large concrete structures such as [[dam]]s, [[navigation lock]]s, large mat foundations, and large [[breakwater (structure)|breakwaters]] generate excessive heat during hydration and associated expansion. To mitigate these effects, ''post-cooling''<ref name="BerkCE">{{cite web|url=http://www.ce.berkeley.edu/~paulmont/165/Mass_concrete2.pdf |title=Mass Concret |archive-url=https://web.archive.org/web/20110927073606/http://www.ce.berkeley.edu/~paulmont/165/Mass_concrete2.pdf |archive-date=27 September 2011 }}</ref> is commonly applied during construction. An early example at Hoover Dam used a network of pipes between vertical concrete placements to circulate cooling water during the curing process to avoid damaging overheating. Similar systems are still used; depending on volume of the pour, the concrete mix used, and ambient air temperature, the cooling process may last for many months after the concrete is placed. Various methods also are used to pre-cool the concrete mix in mass concrete structures.<ref name="BerkCE"/>

Another approach to mass concrete structures that minimizes cement's thermal by-product is the use of [[roller-compacted concrete]], which uses a dry mix which has a much lower cooling requirement than conventional wet placement. It is deposited in thick layers as a semi-dry material then roller [[compactor|compacted]] into a dense, strong mass.