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Comment by LegitShady | Hacker News Reader

How often do you think most concrete structures (with only minor cracking like in the article) undergo serious rehab? Maybe once in their service life.

Also, when planners are choosing between alternatives, net present value (NPV) is calculated which takes into account predictable maintenance, so the cost of future repairs is already considered in these decisions.

Civil engineering is also not computer engineering. There is no agile development and you have to get it right the first time. The industry as a whole is not quick to adopt new technologies without seeing them proven in the field relatively thoroughly.

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> Civil engineering is also not computer engineering. There is no agile development and you have to get it right the first time.

Eh, that's a little overstated. You'd be surprised how many buildings and bridges have major refits when it becomes obvious that their design didn't live up to expectations.

design flaws can't be fixed by bacteria, so will not be stopped from using this concrete.

Predictable maintenance is already factored into decision making.

Fixing mistakes in structures you have to take apart gets very expensive quickly.

There's a youtube video about a hybrid version of that, some famous civil engineer forgot a tiny detail in a massive project. Student of his raised the issue, he actually listened, and managed to plan a last minute redesign/overhaul without anybody knowing (at first).

It's the Citicorp tower you're talking about.

most probably, and thanks to you, I found the video again

https://www.youtube.com/watch?v=Bv2YQnT6pSo

There's this youtube video, I won't link to it, but its awesome. I haven't seen it myself, my wife has, and she told me it was amazing. Its youtube, the video, super student vs teacher thing, overly amazing, much overhaul, legit story.

May be it's true for Europe, but in my country they're re-building roads every few years. Not sure if they are agile or just corrupt...

Qualification: I can't really confirm this fiscal responsibility of this.

Vermont is of the opinion that resurfacing roads frequently (like every two years) is cheaper than investing in anti-frost heavy road beds and cement... The reasoning behind this is that intense ground freezing can end up upsetting the best bedding techniques and causing frost heaves anyway - that coupled with frequent ploughing to deal with heavy snow fall makes long term road investments fiscally irresponsible. Also the state has frequent flooding issues which can upset road bedding in more different and fun manners.

depending on how plastic the soil, replacing it with the road base doesn't stop deformation just slows it down. If the base material is heavier than the native material it will speed the whole thing up.

Then you get into the territory of lightweight fills and it gets really expensive very quickly even beyond basic roadbuilding.

the complexities of road construction depend on all sorts of factors from weather, subgrade composition, labour and material costs, traffic weight, total traffic, availability of capital, willingness to take risks, etc etc.

Most likely the roads are not being "rebuilt" but rather getting microsurfacing, and occasionally a mill and inlay of just top layers of the road surface. Fully rebuilding roads is more time consuming.

Ive been enduring a rebuild of I-294 around Chicago. It's around a 40 mile rebuild (ripping everything out down to dirt), IIRC. They're widening the highway in stretches, completely redesigning interchanges as well to remove sharp turns so that semis can keep speed and better merge. Lots of overpasses and other bridges being rebuilt to accommodate the extra lane each way. They completed the stretch around Ohare airport pretty quickly, in about a year, but seeing the materials used, I doubt it will hold up over time. I expect it will need maintenance on the first completed stretch before the 10 year project is complete. They went from concrete to an all asphalt layering from what I saw. Doubt it will hold up.

Edit: designing -> redesigning.

I’ve been seeing a lot of concrete get torn up and replaced with asphalt here in Illinois, all over the Chicagoland region. It’s a shame.

Additionally, something I’ve noticed is cutting out squares of broken asphalt around a pothole and filling that, only repeated every few feet to make it look like a patchwork quilt. I get that it is cheaper, but it’s not even going to last through a single winter...

asphalt can be designed for similar loading to concrete, and can be easier to repair and replace. Oil may have been cheap so asphalt may have been cheap reducing the cost significantly even with future maintenance.

Hard to say without knowing the details. Asphalt is not garbage and the only people I know who can evaluate it by sight work with it routinely.

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