Indeed. One need only look at a few DIY sidewalk repair jobs to see what happens to unreinforced concrete in relatively short order. This article doesn't ment

Indeed. One need only look at a few DIY sidewalk repair jobs to see what happens to unreinforced concrete in relatively short order. This article doesn't mention what the usable cure time is, but the magic of Roman cement is that it continues to get harder over centuries.[1] [1]http://www.sciencemag.org/news/2017/07/why-modern-mortar-crumbles-roman-concrete-lasts-millennia http://www.sciencemag.org/news/2017/07/why-modern-mortar-cru...