3 ms·

This can be the period the construction engineers are responsible or the worst possible exploitation conditions. My estimate is 200 - 300 years if roof is maint

This can be the period the construction engineers are responsible or the worst possible exploitation conditions. My estimate is 200 - 300 years if roof is maintained well and no pipe leaks inside.

lazide 5y ago
Worst possible conditions usually involve seawater, acidic conditions, and/or moisture. Even without those factors it’s rare for reinforced concrete to last more than 50 years. The more protection from the elements, the better of course. Most concrete structures with long design lifetimes made of concrete (some dams, levees, bridges - but not all by any stretch) will use design techniques to minimize or remove the use of rebar, such as compression only designs , or ‘overbuilding’ so expected corrosion still leaves the structure strong enough over it’s design life. Generally, concrete is a strongly base compound and protects rebar from corrosion. Over time however it can be influenced by the environment, with those base compounds reacting and leaving a less protective environment. Some environments do it faster than others. If the covering concrete is strong enough/thick enough, the pressure caused by the rebar turning to rust inside the concrete won’t crack it - if the rebar was structurally important (pretty much always or why use it?) it still weakens the structure though, sometimes dangerously. Attempts to mitigate the risk where weatherproofing is not an option and rebar is essential for structural reasons like concrete roadways and bridges have had their share of disasters. epoxy coated rebar for instance can lead to unpredictable and sometimes rapid failures in exactly the types of environments it was expected to help in [https://www.fhwa.dot.gov/publications/publicroads/99novdec/rebars.cfm https://www.fhwa.dot.gov/publications/publicroads/99novdec/r...] https://partridge.com.au/concrete-cancer-what-is-it-and-what-does-it-mean/ https://partridge.com.au/concrete-cancer-what-is-it-and-what... Some other failure modes include the Alkali-Silica reaction (sometimes confusingly named concrete cancer too, though fundamentally different) [https://en.m.wikipedia.org/wiki/Alkali–silica_reaction https://en.m.wikipedia.org/wiki/Alkali–silica_reaction] The more dependent a design is on an element that can corrode, and the tighter it’s design tolerances, the more fragile it is. The more overbuilt it is, and more conservative the design, the more expensive it is. Taking a low margin design and then not maintaining it is a recipe for this kind of disaster [https://www.google.com/amp/s/www.independent.co.uk/news/world/europe/genoa-bridge-collapse-engineer-riccardo-morandi-warning-corrosion-rust-concrete-a8498716.html%3famp https://www.google.com/amp/s/www.independent.co.uk/news/worl...] and lots of dead people.

This can be the period the construction engineers are responsible or the worst possible exploitation conditions. My estimate is 200 - 300 years if roof is maintained well and no pipe leaks inside.

lazide 5y ago

Worst possible conditions usually involve seawater, acidic conditions, and/or moisture. Even without those factors it’s rare for reinforced concrete to last more than 50 years. The more protection from the elements, the better of course. Most concrete structures with long design lifetimes made of concrete (some dams, levees, bridges - but not all by any stretch) will use design techniques to minimize or remove the use of rebar, such as compression only designs , or ‘overbuilding’ so expected corrosion still leaves the structure strong enough over it’s design life. Generally, concrete is a strongly base compound and protects rebar from corrosion. Over time however it can be influenced by the environment, with those base compounds reacting and leaving a less protective environment. Some environments do it faster than others. If the covering concrete is strong enough/thick enough, the pressure caused by the rebar turning to rust inside the concrete won’t crack it - if the rebar was structurally important (pretty much always or why use it?) it still weakens the structure though, sometimes dangerously. Attempts to mitigate the risk where weatherproofing is not an option and rebar is essential for structural reasons like concrete roadways and bridges have had their share of disasters. epoxy coated rebar for instance can lead to unpredictable and sometimes rapid failures in exactly the types of environments it was expected to help in [https://www.fhwa.dot.gov/publications/publicroads/99novdec/rebars.cfm https://www.fhwa.dot.gov/publications/publicroads/99novdec/r...] https://partridge.com.au/concrete-cancer-what-is-it-and-what-does-it-mean/ https://partridge.com.au/concrete-cancer-what-is-it-and-what... Some other failure modes include the Alkali-Silica reaction (sometimes confusingly named concrete cancer too, though fundamentally different) [https://en.m.wikipedia.org/wiki/Alkali–silica_reaction https://en.m.wikipedia.org/wiki/Alkali–silica_reaction] The more dependent a design is on an element that can corrode, and the tighter it’s design tolerances, the more fragile it is. The more overbuilt it is, and more conservative the design, the more expensive it is. Taking a low margin design and then not maintaining it is a recipe for this kind of disaster [https://www.google.com/amp/s/www.independent.co.uk/news/world/europe/genoa-bridge-collapse-engineer-riccardo-morandi-warning-corrosion-rust-concrete-a8498716.html%3famp https://www.google.com/amp/s/www.independent.co.uk/news/worl...] and lots of dead people.