[FoRK] KK: the art of endless upgrades

Stephen Williams sdw at lig.net
Wed May 18 00:47:27 PDT 2011

On 5/17/11 11:39 PM, Eugen Leitl wrote:
> On Tue, May 17, 2011 at 04:58:11PM -0400, Gary Stock wrote:
>> On 5/17/11 10:04 AM, Eugen Leitl wrote:
>>> I can see very permanent
>>> things decay in my own lifetime. Surprising, asphalt doesn't last forever,
>>> nor do iron and even stone.
>> I recall a class in Segovia, touching on design features of the
>> aqueducts built there ~2,000 years ago.  The professor noted that they
>> may remain standing (and essentially functional) that long again --
>> perhaps longer.  He then commented on the pomposity of our use of steel
>> rebar to "improve" concrete construction.  In half that time,
>> archaeologists will be either confused or amused by the little round red
>> holes -- hollow tubes where those steel bars once were -- presuming any
>> of the concrete remains intact.
> Actually the rusting iron expands, and breaks up the concrete

Stainless steel might be interesting.  Or fiberglass.

> matrix from within. The Roman concrete was not reinforced, and
> remarkably sophisticated:
> http://www.geopolymer.org/archaeology/roman-cement/high-performance-roman-cement-and-concrete-high-durable-buildings

Very cool.  And apparently we've rediscovered equivalent methods for specialty cements.  Those must be more expensive or 
something.  I rebarred, formed, had poured, and shaped a few cubic yards of 4000PSI concrete several years ago (with underground 
conduit).  It was _no fun_, but came out great.  For many applications, you probably don't want something too indestructible in 
case you change your mind.
> Arguably today we could use mineral fiber reinforced concrete
> or geopolymer, and achieve much better durability.


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