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I'm not sure as I'm not a builder or plasterer and it does depend on the use case.

However I do know that some grout and some paints that say they are anti-mold contain Lime or calcium hydroxide as their primary anti-mold ingredient. I think pure Lime putty can be used as pointing material between bricks in humid basements. Lime plaster (lime mixed with sand) can also be used in bathrooms (with some considerations I am not familiar with). So, my best guess is that some mix of Lime can be used as grout. But I can't say for sure.

Something I plan on doing before this winter is to use Lime Wash. Take Lime (CaOH2 in powder form) and mix with water until it has milk like consistency and brush it on grout or on (white) bathroom walls. If it works, I expect it to be a yearly or quarterly ritual and not a one time solution.

EDIT: A fascinating historical material I recently learned about used in bathrooms is called Tadelakt [1] which uses Lime as one of its ingredients.

[1] https://en.wikipedia.org/wiki/Tadelakt

There is a variation of lime wash that includes a fatty oil as a sealant and has been around for 100s of years

https://en.wikipedia.org/wiki/Tadelakt

In my experience, grout doesn't go mouldy but silicone sealant certainly does. It's the caulk and the sealant that you want, i think, to replace

Pure silicone caulk is mold-proof, even in the white variation. The various "improvements" in many caulks allow mold to get a foothold.

it's not waterproof

You are correct.

I'm not sure why I remember cement to be water proof. Its possible I infered from how its been used around me. I have seen cement very often used where water contact is expected (bathrooms etc). I have also seen brick walls plastered with an extra layer of cement as putty considered to be rain proof and any leaks were thought of as poor workmanship rather than poor material choice.

P.S. I'm not a builder. I've taken an interest in the topic a few months ago.

You can also just see it with cement board - if you pour water on top of it, it will eventually migrate through and drip.

The key here is “based on Portland cement”, which is generally has water repellent added to it making it water proof.

Normal cement, concrete .. Is a different story.

> Lime takes a while to set (a few days?)

Up to 30 days to set, and depending on the type of lime (hydraulic or non-hydraulic) and form/process (putty, hot mix, etc.) up to a year to reach full hardness.

Cement will still take many days to reach full cure time (measured in increasing PSI ratings)

https://www.ce.memphis.edu/1101/notes/concrete/section_3_pro...

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> Stainless steel rebar is a thing. It's expensive […]

That's an understatement. Fiberglass (GFRP) tops out at roughly US$ 2.50/foot, while SS can get up to $9:

* https://www.wellcoindustries.com/the-cost-of-rebar-and-the-c...

The low-end of plain steel rebar is $0.40.

There's also Glass Fiber Reinforced Polymer rebar but I don't know much about costs and how good it is vs stainless steel rebar.

> Stainless steel costs much more, but total project cost goes up less than 10%.

I think people are often surprised how little materials cost affects the total cost of a job.

I'm having this argument at work, where I want some more expensive cabling installed in a bunch of offices across Scotland so it doesn't need to be done again in another ten year's time, but "that stuff is so expensive, do we really need it?" is what I'm running up against.

So as it turns out today I'm giving them a breakdown of the cost of the job. Guess what the expensive bits are?

Did you guess "wages for two guys, hotel rooms for two guys, 800 miles of diesel, and a couple of ferry tickets?"

Well, you're way ahead of today's crowd then.

> Two piers were built in the 1940s, side by side

As far as I can tell, only one pier was built (using stainless steel rebar) and the presentation is comparing it to a hypothetical alternative as a theoretical exercise: "What if the Progreso Pier was built using carbon steel rebar?"

To build without tension you have to build structures that basically look like Roman structures [1]: a bunch of tightly spaces arches so that the entire thing is in compression, with no meaningful tension anywhere.

But it turns out that's pretty inconvenient; we really like doing dozens of feet of span for highway overpasses, building floors, and everything else. So we put rebar in all the concrete and just acknowledge that that means it has an absolute maximum lifespan of a century or two, and will certainly not last for millennia the way pure concrete in pure compression can.

[1]: https://www.theartnewbie.com/blog/rome/roman-arch

> Wouldn't your beams start cracking at the bottom, where they are subject to traction?

You have a few mistakes here. I’m not trying to demean you, but I’m going to number them just for clarity, as it can get confusing when there are many misunderstandings.

1. You are intending to ask about tension (which the rebar helps with), not traction (the force your tires exert against a road).

2. Tension is not only experienced at the bottom of beams, the location with the most tension will depend on the geometry. For a vertical beam, I think tension will probably be pretty even through the whole beam in most “normal” designs and loading configurations. But it will really depend on the geometry and on the loads being applied.

3. I think when you say concrete beams you’re meaning columns (apologies if I’m wrong about this). Concrete columns are remarkably good at holding up without rebar, because they experience almost exclusively compression! And indeed, ancient Roman designs did not use rebar at all :). It’s certainly possible.

> exactly the opposite

No, steel is better in both ways, ten times over. It's just more expensive, concrete is a "filler" to cheap out construction.

If you think about it, all engineering is about cheaping out things. It's pretty easy to build awesome projects having unlimited budget.

Just FYI, I think you're looking for "(in) tension" instead of "(on) traction".

There's also stainless steel rebar

A broader view of this point would be "the economic structures in some countries do not allow for investments with a long payback".

I’m passing my latrine down to our great grandchildren.

This is something I wasn't aware of that is fascinating. The ph balance of the rebar's environment determines the progression of oxidation. There was a guy in the 1920's who observed this and had the idea to put cement in paint; it was so successful he renamed the company to cement spelled backwards.

  Inside the concrete, Ca(OH)₂, which is generated by the hydration of cement, 
  creates a strongly alkaline environment, with a pH value of more than 12.7. 
  In this environment, a passivation film forms on the surface of the rebar to 
  prevent corrosion. However, the pH of the concrete decreases as micro-cracks 
  develops and chloride from the outside infiltrates the rebar. Eventually, as 
  the environment inside the concrete becomes neutralized, the corrosion of the 
  rebar accelerates, which reduces the overall durability and stability of the 
  reinforced concrete structure.

  A sighting of preserved steel reinforcing bars sticking out of old concrete 
  rubble piqued the curiosity of our company founder, Albert C. Bean, Sr. After 
  investigating this finding, his company, Armor Oil & Chemical Company, began 
  producing a patented cement-filled coating formulation that, in its updated 
  form, still protects structures from corrosion today.

Yes, but you have to replace the sacrificial anode every so often.

https://en.wikipedia.org/wiki/Galvanic_anode

Coated rebar could be good, but the coating can be damaged anywhere from manufacture to installation.

The myth is that Roman concrete was 'better' and that we don't know how to recreate it. The facts are that it was not better in any way than what we can do now and we have always known how to replicate it. Grady addresses both of those aspects of the myth in the video, and the first part is literally the title of the video: "Was Roman Concrete Better?"

The answer is no. What is true is that some Roman concrete structures (but far from all of them) are extremely durable because they were optimized for a different set of requirements than modern buildings usually have, notably "needs to last forever as a symbol of the emperor's power". From the 19th century on that has very rarely been a design constraint, so we optimize for other things instead.

No, for two reasons.

First, we can’t summon infinite money to pay for things. Paying 10X more per bridge means we can build 1/10th as many bridges or we have to start stealing from other budgets.

Second, we don’t know what the needs will be for the bridge in that location 100 or 1000 years from now. It could need to be torn down to be widened. Maybe we’re all riding around in electric vehicles that coordinate perfectly with each other and the bridge isn’t needed for cross traffic any more. We don’t know.

No, because there are public projects that make sense at 3–4% discount rates that haven't been funded, so it would clearly make more sense to direct funding towards those projects first before trying to fund anything that requires a sub-1% discount rate.

The thing is, we're actually pretty crappy at knowing what we'll need 50 years from now, much less 500. Doesn't make sense to overbuild for an unknown future, when hundred years from now us will likely be able to do a far better job anyway.

But it's also true that modern world changes much faster than in the antiquity. If you built a church, a market, and a few utility buildings like tavern and blacksmith in 500BC you could rest assured they'd still remain used in 1000 years practically unchanged unless the structure or wider economy collapsed. Meanwhile "office building, shopping mall, nightclub, school" all varied highly in popularity within last 50 years, and it's difficult to convert one type of building to another, not to mention the costs of modernizing an old building.

but not ones willing to put the effort into properly fixing a pond.

We don't build better bridges than we did 200 years ago? Forgive me if I'm wrong, but it seems like we build bridges right now that would have been unthinkable 200 years ago

This is exactly what we did with houses, buildings. We had perfectly functional 100+ years old fully functional, gorgeous buildings and we replaced those with brutalist concrete/glass barely functional garbage.

Usually you need wider bridges, so the old bridge needs a replacement or a second bridge on the side.

But we are currently doing it when a bridge can't handle modern traffic levels because it was designed thinking in 50's traffic (single lane for each direction without peatón or bicycle ways to 4 or 6 lanes and pedestrian and bicycle ways).

In fact, the dominance of concrete is surprisingly political. It has a lot to do with Cold War geopolitics

https://www.listennotes.com/podcasts/the-conversation/keepin...

Case in point, Roman concrete

The Eiffel Tower dates from the XIX century. Pre the shift to originality. Which XX century building in Paris is objectively beautiful? The tour Montparnasse? The Centre Pompidou? Or Jussieu’s campus? Even the Opera Bastille is pretty lame, not outright ugly but lame.

It is not.

You can make sand by crushing rock, we don't because it is cheaper to extract natural sand. Should we run out of suitable natural sand, we will just have to go with the more expensive option, not a big deal.

A curiosity is one thing. But where is the wow factor you get when you enter Rome’s pantheon?

I'm also judging by my own eyes because I can see that the WPA concrete uses coarser substrate like the Gemini answer says and is harder than normal concrete when I press it. And also has no cracks in it almost 100 years later.

I don't see how this would work because you're saying that the older sidewalks are scrapped and rebuilt when they hit a state of 'x' deterioration, so you only see > 'x' state ones. But how then could it be that newer sidewalks are allowed to fall below 'x' instead of also just being scrapped and rebuilt?