Cool stuff -- author doesn't mention that Roman cement had a usability life of >2000 years, while Portland cement starts to degrade after 50 years (for rough ha

Cool stuff -- author doesn't mention that Roman cement had a usability life of >2000 years, while Portland cement starts to degrade after 50 years (for rough harbor usages). http://www.bloomberg.com/bw/articles/2013-06-14/ancient-roman-concrete-is-about-to-revolutionize-modern-architecture http://www.bloomberg.com/bw/articles/2013-06-14/ancient-roma...