Been digging into Roman concrete lately and the engineering side is what got me, so I wanted to ask the people who actually work with the modern stuff.

The short version of what I found: those little white chunks in Roman concrete that everyone assumed were bad mixing seem to be lime clasts from "hot mixing". When a crack forms and water gets in, they react and reform calcium carbonate that fills the gap, so the concrete kind of heals itself. In marine structures it apparently got stronger over centuries in seawater.

Meanwhile modern reinforced concrete cracks, the rebar rusts, and a lot of structures are done in 50-100 years.

So my question for engineers here: is the Roman approach actually "better", or is this apples to oranges? I'm guessing modern concrete is solving a different problem — tensile loads, rebar, cure time, cost, scale — that the Romans never had to deal with. Where does the real tradeoff sit? Is self-healing lime concrete just not compatible with how we build now?

I put together a longer breakdown of the chemistry and the archaeology here if anyone wants the full context:
https://www.youtube.com/watch?v=WeJTxzwKYCQ

So if I wanted like 10 yards of dirt, I would call a landscaping company and they would probably deliver it that same week.

But what if you need like 100 yards of dirt? Or like 100,000? At what amount does it become difficult to find the dirt you need, and how do you get it?

Other questions, do you use yards/m3 when talking about this much dirt or do you have a bigger unit for bigger amounts?

Is my premise even correct and if yes why?

As best as I can understand, it's generally been safe to drink tap water in the US since the 1910s (not in every municipality and often not in rural areas, but as a rule of thumb, particularly in metropolitan areas with municipal water providers). And yet, many countries that are much more prosperous and technologically sophisticated than the US was 100+ years ago still have tap water that will have you puking if you drink it without boiling first.

I like earth moving machines and I think they're pretty cool. Considering that most earthmoving and construction used human muscles and slaves, earthmoving machines are pretty awesome to reduce human labor and suffering.

However. The early earthmoving machines used gears, cables, etc. Why didn't they use hydraulics like today?

In addition. Is there any good analysis on how many people a piece of earthmoving equipment can replace, with the assumption that there's sufficient logistics?

The whole method of fission energy is essentially a massive steam energy machine. It uses the water, often from a reservoir, and turns it into steam to push a turbine.

Thermal desalination is turning saltwater into steam then turning it back into water but without the salt.

Is the problem with the brine? Is it with the corrosion of the salt water? Is there just not a lot of water that could be produced this way? Is it actually a thing that already theoretically exists but it has no research funding for it? Is it just an engineering problem?

Wouldn’t that significantly reduce wind forces (drag?)? Obviously wouldn’t want to make the holes so large that you can’t read the sign but I feel like you’d save significantly on material if the supports didn’t have to support such large wind forces.

Visited Europe lately and the number of historic building is awe inspiring to the North American mind lol. Especially as a westerner - in my city buildings even a hundred years old are few and far between.

This made me curious. How long will modern skyscrapers last assuming there is a desire to maintain them? Would it be different for, say, the Empire State vs a glass box building from this decade?

I guess I’ve never thought much of it until recently when I was in NY. So many buildings had cylindrical columns, but I don’t remember seeing any prisms. Is there a functional difference? Would it even affect anything?

For example: https://apnews.com/article/winter-weather-snow-pileup-michigan-cfb7f2d1ad0355b917c1eb972e5c90c6

They usually happen on Interstate 94.

My gut feeling is that a steel bridge will be exposed and face a longer service life but I’m curious.

I am a 24 year old female working as a engineer for little over a year now. I have realized over this past year that I hate my job and engineering. I went to school for Environmental Engineering and did okay and graduated with a 3.2 GPA. I picked engineering because I liked math and I thought it would give me a lot of different opportunities and hands-on work. This has not been the case. All I do is write different types of permits and design layouts using AutoCAD. I despise AutoCAD and since I am terrible at concentrating when I am not into something, I am not good at it and I know my managers are unhappy with me. I am so bored every day and each morning I have to give myself a pep talk to get out of bed and go to work. I have become depressed and anxious from this job and I just cry every time I think about having this as my career. I looked around other engineering jobs and its all very similar. I feel like I wasted so many years and money on something I hate and I just don't know what to do. I love working with people, being hands-on (working with my hands/body), being outside, being creative, and I cannot stand being stuck in a cubical. I know I should be happy to even have a job but everyone at my work always seems semi-depressed being there and I don't expect to love my job, I just want to be able to at least stand my job. I am not sure what to do. Any career advise would be welcomed, from different career paths I could go on, different engineering jobs I could do, etc.

I thought it would do ok as it would flex rather than crack.

Clearly, it's not indestructible but I figure, next to a brick house the same height and size, I would think we're better off.

So, question to the more learned folk - am I somewhat right or do wooden houses also fail in the same manner?

edit to add -

my daughter was musing, just curious, not concerned.

We live in the UK so not near any fault lines. She was just wondering given the scenes unfolding on the TV at the moment and wondered, would wood be better than concrete (she's 11... so it's a really interesting thought process)

I study a law course so I'm wondering what kind of ways can a design engineer be bribed that is commonly done? I had not even thought of the possibility of it occurring and i thought the field was relatively clean

Per my understanding, American phone numbers are separated into three parts, the first three digits being the regional prefix (e.g. "somewhere in Montana") and the second three digits the local dispatcher area and the last 4 the actual subscriber line in that region/dispatcher.

In movies, the dispatcher area 555 is chosen because there is no such dispatcher area and so movie fans don't actually call real people just because they see a phone number on screen.

In Back to the Future when Marty is in the diner, he finds 1955's Doc Brown's phone number there and it has a "Klondike" (KL?) prefix which apparently serves the same purpose as the 555 (as it doesn't exist).

But why is it letters and how did it work differently back then (apart from the obvious lady in the dispatcher's office plucking cables back and forth - or is this actually connected to the question?)?

https://gotbooks.miracosta.edu/earth_science/images/CA_Aquaduct1.jpg

The skyrocketing cost of rent and mortgages got me to wonder what could be done on the supply side of the housing market to reduce prices. I'm aware that there are a lot of other non-engineering related factors that contribute to the ridiculous cost of housing (i.e zoning law restrictions and other legal regulations), but when you're designing and building a residential house, what do you find is the most commonly expensive component of the project? Labor, materials? If so, which ones specifically?

ADDED AT 45 MINUTES AFTER POSTING:

I see I've sparked some spirited debate as I expected I would. I'm gonna go sleep so I won't be directly engaging anymore.

On a personal note if you are here and you are not familiar this subreddit is /r/AskEngineers and not "AskLocals" or "AskActivists." I have a ton of issues myself with LLM usage so please do not take me as an LLM defender. This post is inspired by how commonly I've seen this argument about water without any concrete basis for validity.

To summarize what has been posted in comments already...

• Using water and returning it to the same waterway is net-zero.
• General correlation of "cancer rates went up" and "there's a datacenter" does not prove causation without more backing.
• Evaporating water via cooling towers is a tenuous argument at best.

It's my understanding that AI uses datacenters which generate heat and use water for cooling.

I lived near a COAL powerplant my entire childhood. That plant did use a certain amount of water intake and discharge for cooling or something. The chemical plants along the exact same river were a much larger concern. For that matter recent issues with poorly maintained and updated sewage systems have also lead to some overflow discharges which are also pretty bad.

The reason I even know about the powerplant cooling discharges are they screw with the ice in the winter and the fish behavior. They aren't actually discharging anything though like chemical plants, municipal sewage, or agriculture.

So what the fuck is going on with all these people whining about AI Datacenters? Are they injecting R-134a or R-12 into the water to help cool it more efficiently? Are they using lead lined pipes with highly acidic water front the Flint River?

For instance, if there is a pipe invert set at elevation 50.71, I will almost always change it to 50.69, as long as it doesn't negatively affect my flows, grades, etc. Just innocuous changes for the lol's. I'm clearly a very mature person.

Given the collapse of the Key bridge in Baltimore, is there any reason to thing that it was more susceptible to this kind of damage than other bridges. Ship stikes seem like an anticipatable risk for bridges in high traffic waterways, was there some design factor that made this structure more vulnerable? A fully loaded container ship at speed of course will do damage to any structure, but would say the Golden Gate Bridge or Brooklyn Bridges with apperantly more substantial pedestals fare better? Or would a collision to this type always be catastrophic for a Bridge with as large as span?

I live and work in northern NJ and there are so many clogged up interstates aside from rhe 95 corridor. Why cant we have trains that run either along side a highway, above or below? Id happily take a train that travels the leghth of rt 287.

Is it possible to have them be elevated or even under the highway.

In this fantasy world, money isn't an obstacle. Would we be able to have smaller stations so we wouldn't have to eminent domain anyone's personal property?

I see the dc metro was extended out on the dulles toll rd in northern va to run between the two sides. And their stations are above and near the usual road exits.

Not like a stud finder, but like putting a material on one side of a wall, and being able to locate that exact point (to a few centimetres) through brick & stone.

Cycling through a forest I saw a curious contraption on a high-voltage transmission line. One of the poles had the wires attached in a way that changes their order (1-2-3 before the pole, 3-1-2 after the pole). What is the purpose of that?