Roman concrete durability

Mentioned as a possible student presentation topic; Tom notes Roman concrete has lasted two thousand years and there are recent scientific articles on why.

So natural fiber reinforced concrete. Lots of good issues there. Natural fibers tend to decompose — organic fibers rot. But we've been using them to make bricks since the days of Moses and before. Can't make bricks without straw. But what are the issues if we want to use it for concrete? And there's the issue of Roman concrete and why Roman concrete is better than any other concrete. There are articles on that.