[Greenbuilding] Unconscionable Concrete Use

[John Straube]

There has been a lot of research, some of it backed by significant venture funding, into lower C02 concrete
I agree with John Salmen— the biggest issue is that people dont design to use the required amount, they just use a lot os that they dont need to spend extra design or construction labour.

We have in the last 50 years improved on concrete by adopting some of the Roman approaches: ground blast furnace slag and fly ash (both the result of outputs from industrial processes that used to be deemed waste) and silica fume, are now widely used by all major suppliers of cement and concrete in North America because they make better concrete at lower costs.
The lime used by the Romans produced a LOT of carbon dioxide, and modern lime production is not much better— the lowest CO2 emissions are made from modern natural gas powered plants, not lime kilns vs cement kilns.

The way the Romans made very durable concrete was two fold— 1. they rarely embedded steel or metals in the concrete (it is the embedded steel that causes most durability failure in modern concrete structures) and 2. they made up for the lack of steel by using a LOT of mass concrete pours and arch shaped/compression only structures.   Oh and the avoided building in areas away for freeze-thaw zones  :)  We could do the same today but the thinking is: why spend $1million dollars for a bridge with 500 yr durability when you can spend $750000 on one with 50-60 year durability?  

PS. I am also dubious that they used seawater.  Never heard of how to use seawater without causing performance problems in lime or cement.

On Nov 21, 2015, at 3:38 PM, Peter/Pam Martin <p2j2 at shaw.ca> wrote:

> Learned in an article at http://www.ancient-origins.net/history/ten-things-ancients-did-better-us-004557 that the Romans made concrete by mixing lime, volcanic rock, and seawater that contained the ideal crystalline structure of Tobermorite. Purportedly the Roman concrete had a greater strength and durability than modern concrete as well as only requiring baking the limestone at 900°C. Any present attempts at duplicating this process?
> 
> Another concrete observation: I've been watching a series on public TV called Grand Designs where the builders use inordinate quantities of concrete, with some of the slab pours having the consistency of soup. Is this normal practice in the UK? It reminds me of the building methods of Mike "I don't use one stud when I can use five" Holmes.
> 
> Peter
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John Straube
www.JohnStraube.com