There’s recent studies that show old cement from Chinese historic locations have continued to increase in strength beyond what modern cement and concrete does. There’s been some papers/studies on reconfiguring modern concrete to match the old formulas.
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The reason it’s so hard for him to make cement is because he’s in Australia, not ancient Rome. He doesn’t have the right geography.
I saw a guy on TV make a concrete column section such as you’d find in ancient Roman buildings, this was his method:
- build campfire on Roman beach rich in volcanic deposits
- kick the limestone rocks of your fire-ring into the fire
- scoop up ash, sand, and burnt limestone to fill wooden mold
- tie rope around mold and throw into the sea
- tie rope to stake pounded into beach above tide lines
- wait one lunar cycle (28 days)
- pull out your completed concrete object and use
There are additional optional steps for singing, drinking beer and making s’mores around the campfire, but the guy on TV skipped those.
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I mean why even bother if you’re going to skip those.
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Wait, what’s anti-philandering pizza got to do with this?
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That’s dependent on the mix, to some extent. You can change the cure time and strength of cement just by adding more or less water. In general, the less water you use, the stronger the final product, regardless of whether you’re making mortar or concrete. But more water makes it easier to mix, and to fill forms if you’re making concrete, so people often overdo it.
Expert masons (I am not expert, just experienced) will vary the mix with temperature and expected humidity and underlying soil conditions and stuff like that to try to get an optimal 28 day cure; personally, I believe this custom dates to ancient times, and is because masons of old used the moon as a scheduling aid. “I have other jobs for other nobles, milord, I will come back when my awesome mason secret knowledge tells me your foundation is cured” means “I’ll come back when the moon looks the same as it does tonight”.
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Not saying Native American shell middens didn’t assist the process in some locales, but the coastal areas in general seem to have more shells just washed up from wave action than he has available. Unless he stumbles across an aboriginal Australian midden? Can’t see why the natives there wouldn’t eat shellfish. Anyway, I posted that before I read about his experiments with snail shell lime. Overall, it looks like he is better off sticking to alternative mortars, I have seen pine tar and horsehair used in old house foundations. Or maybe just focusing on wattle&daub, adobe, or cob type structures like he has been.
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It’s australia. If I lived there I’d assume the shellfish were poisonous, too.
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There’s a DIN for that…
Actually, more than one.
The wait-a-bit period was more important when cement/concrete was mixed by hand on-site from ingredients of variable quality.
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He may not be working in a suitable location. If he’s far from a suitable body of water - and I don’t recall seeing anything in any of his videos - then snails might be the best he can do. Pretty labour intensive though…
They were keeping kosher??
I am an admirer of DIN because all my finest wrenches say that on them 
But I don’t know how you’d work weather prediction into a standard :scratches head:
I mix on-site with a cheap electric mixer because it costs way less. I used to mix it up in a tub with a hoe, but I’m too old for that stuff now! Buying a 3½ cubic foot volume (a bit over 100 kg weight) mixer costs less than renting one three times, and mixing my own mortar and concrete would be less expensive than buying bags of premix even if I wasn’t using stone and gravel gathered from the property and sand from mostly free sources.
Even so, just the fact that I buy commercial Portland cement as the basis of the mix means I have radically better quality control than ancient or medieval masons far more skilled than I.
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