Cement and concrete

[Probeman]

I thought there must have already been a topic on cement and/or concrete but I can't seem to find it...

I worked on several cement/concrete analytical projects. One project many years ago for the Oregon DOT when they discovered that some of their bridges and overpasses were corroding much faster than expected.  It turns out that someone there who knew someone (who apparently didn't know as much as they thought they did), had purchased from this person, a numbers of "devices" that purported to reduce the corrosion rates of the re-bar in these structures.

Unfortunately these devices turned out to greatly *increase* the corrosion rates of the rebar!  By now I think all of these damaged structures have been since replaced, but I got to work on these samples and I have to say, concretes/cements are very complicated materials.  The TDI correction certainly came in very handy as some of these materials exhibited a positive slope in their migration of alkalis, which is the opposite of what we normally observe in say alkali glasses.

Anyway, enjoy this story:

https://www.sciencealert.com/we-finally-know-how-ancient-roman-concrete-was-able-to-last-thousands-of-years

[Nicholas Ritchie]

Michael Mengason has rejoined NIST after a couple year absence and is now working on the microanalysis of concrete.  It is a big deal given how extraordinary much of it we use.  Rebar might seem like a good idea and in the short run it is.  Concrete is great under compression but terrible under tension and rebar helps.   But eventually it rusts, the rust expands, cracks the concrete and leads to spalling.