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The rust is essential to bind it to the cement. Without, it adds little strength. Modern concrete isn't expected or designed to last more than a century. It co
by moloch-hai 4y ago
The rust is essential to bind it to the cement. Without, it adds little strength.
Modern concrete isn't expected or designed to last more than a century. It could have been made to last longer, if they wanted, but that would cost a little more. Making no provision for when it will predictably fall apart is a modern failing. That major construction with concrete is about a century old should worry everyone.
We have a very great deal of infrastructure that will fail on a predictable schedule, with nothing budgeted to replace it all.
- saalweachter 4y agoOn the plus side it makes for some wicked post-apocalyptic ruins. Remove maintenance, add 20 years, and you get the most photogenic wasteland you could ask for.
- oakwhiz 4y agoYes although it is true what the grandparent comment said about sealing - that keeping things dry, using coatings or topper materials, dewatering, etc. will all help extend the longevity and reduce maintenance requirements a bit.
- LegitShady 4y ago> The rust is essential to bind it to the cement. Without, it adds little strength. Do you have a citation for this? As far as I know this is entirely not true. Rust is an expansionary product - when steel rusts its volume increases something like 10x, which reduces the connection between the concrete and the steel and causes issues like cracking and spalling. Minimizing rust improves the long term performance of rebar.
- moloch-hai 4y agoThey leave the rebar out to rust a bit, on purpose, before they pour. Surface rust is good, but more is bad. Like many things in life.
- zoklet-enjoyer 4y agoI read your comment as I finished eating my third slice of pie and wondering why I cut myself 3 slices.
- PakG1 4y ago3 is the limit. More than 3 is bad.
- aborsu 4y agoOne would think the limit for pie is closer to 3.14159265359
- PakG1 4y agoIt is, but it's not easy to cut pi slices of pie without being unfair to others who want to have equal slices of pie. Plus, the effort to be so exact may not be worth the utility. You may hit the true pi limit by random luck too.
- imron 4y agoPerhaps you’re just mathematically inclined.
- moloch-hai 4y agoYou could have cut one big slice instead.
- IgorPartola 4y agoRust is perfect. We don’t criticize rust on HN.
- chrisdhoover 4y agoSo the Hoover dam will fail in 10 years?
- moloch-hai 4y agoFortunately, Hoover Dam is under compressive load.
- anamexis 4y agoOnly if the Hoover dam was made with standard concrete using standard building methods, I suppose.
- deleted 4y ago[deleted]
- adgjlsfhk1 4y agoConcrete lasts a really long time when it's under pure compression. You only run into issues when you try to build structures that need to survive in tension. That's when you start having to add rebar and lower weight and you run into issues.
- jcampbell1 4y ago> The rust is essential to bind it to the cement What? This is total nonsense. > Modern concrete isn't expected or designed to last more than a century. It could have been made to last longer, if they wanted, but that would cost a little more. Is hacker news a conspiracy theory website now? > We have a very great deal of infrastructure that will fail on a predictable schedule Wood rots in a few years under certain conditions and can last hundreds in others. Concrete works similarly. The 3rd pantheon is currently standing, but it is a huge mix of repairs across centuries. The Romans built many structures that are similar but now are in ruins because the Catholics didn’t maintain the roofs on bathhouses.
- moloch-hai 4y agoIt is a conspiracy theory that engineering construction is optimized for cost against requirements? Maybe ask literally any civil engineer how much cost matters.
- Slava_Propanei 4y ago[dead]