Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sdd.hp.com!zaphod.mps.ohio-state.edu!pacific.mps.ohio-state.edu!linac!att!cbnews!cbnews!military From: MEDELMA@CMS.CC.WAYNE.EDU (Michael Edelman) Newsgroups: sci.military Subject: Curing concrete Message-ID: <1991Feb8.012544.15685@cbnews.att.com> Date: 8 Feb 91 01:25:44 GMT Sender: military@cbnews.att.com (William B. Thacker) Organization: AT&T Bell Laboratories Lines: 23 Approved: military@att.att.com From: Michael Edelman Thos Cohen asks "how long does it take for 36m of concrete to cure?", with regards to Iraqi shelters. The answer: No longer than it takes 1m to cure. Concrete doesn't harden through drying, but through a process best compared to the production of rock candy :) . Kept wet, the crushed minerals in cement (the portion of concrete which binds the mix) form a number of interlocking crystals. The difficulty in pouring really large structures- like dams- has more to do with stresses set up in the uneven shrinkage and expansion in the mix. A friend of mine who made his living as a rod-buster (that is, one who built steel reinforcing structures used in concrete pouring) tells me that this is dealt with via a combination of techniques involving siad steel reinforcing, different concrete mixes and the like; it seems his experience pouring nuclear reactor containment vessels employs techniques similar to those needed in building underground shelters. --mike edelman medelma@cms.cc.wayne.edu hoover dam fan club medelma@waynest1