Path: utzoo!utgpu!news-server.csri.toronto.edu!bonnie.concordia.ca!uunet!zaphod.mps.ohio-state.edu!pacific.mps.ohio-state.edu!linac!att!cbnews!cbnews!military From: asuvax!gtephx!rakoczynskij@ncar.UCAR.EDU (Jurek Rakoczynski) Newsgroups: sci.military Subject: Re: About those Ugly M-60's Summary: Concrete curing. Message-ID: <1991Feb11.044209.28581@cbnews.att.com> Date: 11 Feb 91 04:42:09 GMT References: <1991Feb5.043146.6128@cbnews.att.com> <1991Feb7.012722.118@cbnews.att.com> Sender: military@cbnews.att.com (William B. Thacker) Organization: AG Communication Systems-Phoenix, AZ Lines: 40 Approved: military@att.att.com From: asuvax!gtephx!rakoczynskij@ncar.UCAR.EDU (Jurek Rakoczynski) In article <1991Feb7.012722.118@cbnews.att.com>, thos@softway.sw.oz.au (Thomas Cohen) writes: > > How long does it take 36m of concrete to cure, or would they put it down > in layers? I worked a few years as a field inspector for a civil engineering firm. While the technology of concrete is complicated, here are a few typical guidelines to use for discussion (1, this is very simplified, 2, references typical, run-of-the mill, average concrete, and 3, from memory 15 years ago): The concrete pour of a slab (like for a roof of a bunker) would probably have been done as a continous pour within the limits of working in the day light, and the strength of the forms to support the horizontal loads of the poured concrete (like a dam). The cure time (and strength of the concrete) is not typically affected by the thickness, to the extent that moisture, temperature, salt (curing agents) remain fairly constant. Don't confuse drying out the surface of concrete with curing concrete. Once you have the proper moisture content, you want to prevent the water from evaporating or being removed from the mix so that the cement can hydrate. The hydration is how the strength develops. Typical 2500 - 3500 psi concrete will achieve % of strength as follows (from memory): 1 day = ~80% max 3 day = ~90% max 30 day = ~95% max and continues to cure for several years. If I am REALLY off, please correct me, but I think it's accurate enough for discussion. -- UUCP: {ncar!noao!asuvax | uunet!zardoz!hrc | att}!gtephx!rakoczynskij Inet: gtephx!rakoczynskij@asuvax.eas.asu.edu Voice: +1 602 581 4867 Fax: +1 602 582 7111