# How does a construction site work?

**URL:** <https://boards.straightdope.com/t/how-does-a-construction-site-work/665849>\
**Category:** Factual Questions\
**Created:** [August 10, 2013, 3:07am UTC](https://boards.straightdope.com/t/how-does-a-construction-site-work/665849 "2013-08-10T03:07:27Z")\
**Posts on this page:** 1\
**Showing post:** 39

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**Author:** ![sich\_hinaufwinden](https://avatars.discourse-cdn.com/v4/letter/s/c5a1d2/32.png) [@sich\_hinaufwinden](https://boards.straightdope.com/u/sich_hinaufwinden)\
**Post date:** [August 11, 2013, 8:55pm UTC](https://boards.straightdope.com/t/how-does-a-construction-site-work/665849/39 "2013-08-11T20:55:02Z")

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> [@Glazer](#):
>
> Just a few years ago the Atlanta Botanical Gardens had a Flying walkway through the tree tops collapse during construction. Seems the steel was rated to hold the weight of the concrete when dry. But was not enough to hold the wet mix. Failed during the pour. The same GC had a parking structure they had previously built fail that same year.

This doesn’t seem right. I thought wet concrete and cured concrete weighed nearly the same amount. That is, concrete doesn’t ‘‘dry’’ from water evaporating. Rather, the water reacts chemically with the cement to become a permanent part of the mix as it ‘‘cures’’.

And this doesn’t even begin to take into account the safety factor that should have been built into the design and for that matter the expected live load of a walkway - that is the weight of the people who would be using it once constructed.

For a walkway to collapse during the pour suggests to me a much bigger problem in design or construction than simply neglecting to consider any difference between wet and cured concrete.

Hopefully an expert in such things will ‘‘weigh’’ in here and set me straight if I’m off the mark. Here’s a quote from a previous thread concerning the weight of wet vs. cured concrete:

> [@weight of cement; cured vs dry](https://boards.straightdope.com/t/weight-of-cement-cured-vs-dry/535589/5):
>
> Former construction material testing tech, here. Yes, the concrete absorbs virtually all the water added to the mix. In fact, the reason you keep it wet while it cures is so water doesn’t evaporate out and weaken it. That said, it forms a fairly small component of the total weight.

in this thread: [weight of cement; cured vs dry - Factual Questions - Straight Dope Message Board](http://boards.straightdope.com/sdmb/showthread.php?t=559128)

ETA: I see Chesire Human has posted in this thread - do I have a correct understanding of your post from the linked thread?

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