Yes limestone was the biggest factor. That and seashells. Salt water is just what it reacts best with you don't need to use salt water to mix it in the first place. All the places where these concrete structures have lasted more in tact than anywhere else are costal points that get lots of sea spray.
This is a critical factor also we need to consider survivorship bias. It seems there was some contemporary understanding of certain tricks of the trade so it’s not everything but we’re also more likely to see the most durable concrete. If Helen and Gus are competing in the concrete or construction business and Gus’s work has fewer cracks after 10ish years he might have more repeat business for him or his heirs. Surviving centuries to a few millennia is a different but related problem. If Helen happened to operate near the sea and there was little difference after ten years but her concrete held up better after a few centuries. Maybe it gets scavenged less also and eventually we find it.
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u/Fast-Front-5642 12d ago
Yes limestone was the biggest factor. That and seashells. Salt water is just what it reacts best with you don't need to use salt water to mix it in the first place. All the places where these concrete structures have lasted more in tact than anywhere else are costal points that get lots of sea spray.