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Why don't we just use concrete by itself? Is steel necessary for using concrete the way we do in modern times?
by silicon2401 5y ago
Why don't we just use concrete by itself? Is steel necessary for using concrete the way we do in modern times?
- namirez 5y agoBasically concrete is good only for compressive loads. Under tension it easily cracks. The steel reinforcement adds tensile strength to concrete.
- codeOnMaster 5y agoIn fact, the concrete MUST crack in the tension zone in order for the steel to take effect and provide tensile capacity to the member.
- kube-system 5y agoOnly if you don’t prestress the reinforcement. https://en.m.wikipedia.org/wiki/Prestressed_concrete https://en.m.wikipedia.org/wiki/Prestressed_concrete
- acchow 5y agoHow often are skyscrapers built using prestressed concrete?
- codeOnMaster 5y agoYes, steel is required. In the design of concrete structure, concrete is assumed to have zero (0) tensile strength.
- PeterisP 5y agoIn order to use concrete by itself, you have to limit yourself to specific architectural structures which are very much unlike modern buildings - essentially, you can build quite high ancient-looking structures with everything held up on arches (which take up space and material), but you can't build a simple box-shaped building from concrete without steel rebar.
- mc32 5y agoIt is now possible to use wooden structural components to build modern skyscrapers. Maybe not 100 storeys buildings but 30 storeys is feasible[1]. [1] https://www.bbc.com/future/article/20171026-the-rise-of-skyscrapers-made-of-wood https://www.bbc.com/future/article/20171026-the-rise-of-skys...
- yodelshady 5y agoFor the way we use it, yes. Concrete works well in compression but is horribly weak in tension; a supervisor of mine compared it unfavourably to a ginger nut biscuit. Probably hyperbolic but you get the idea. Big, arch-y structures like the Roman pantheon work, because everything is in compression. But that's a lot of not-economically-useful space.
- mrfusion 5y agoWhy can’t we use carbon fiber or aluminum or anything that won’t rust?
- dTal 5y agoCost would be my guess.
- toss1 5y agoWe actually can - fiberglass rebar has many advantages over steel, among the first being that it does not corrode and expand. It's also much lighter and easier to transport to and on the worksite. It is starting to see widespread use in the construction industry, but far too slowly. A quick search on "fiberglass rebar" will return many manufacturers and articles.
- UI_at_80x24 5y agoTo avoid the problems of rust, epoxy coated steel is often used. It costs more, so in situations where the contract is won by the lowest bidder (unless it is expressly required), you don't get it. So as a result, buildings that could last 200 years start to crumble after 50.
- baybal2 5y agoEpoxy coated rebar was a trap, and is now being banned around the world. Paradoxically, the epoxy coat can make corrosion worse than the bare steel, let alone galvanised.
- ggcdn 5y agoNot sure why you're being downvoted, because you're right, atleast on the west coast of north america. My firm hasn't use epoxied rebar since like 1990, and we removed all references to it on our drawings long ago. The coatings were super fragile, and often damaged while being placed in the field. Then someone had to come along with magic paint and touch up all the cracks. But of coarse they would never find 100% of them...
- jcims 5y agoGreat video on prestressed concrete members - https://www.youtube.com/watch?v=P13Mau2VUWw https://www.youtube.com/watch?v=P13Mau2VUWw (Really good channel overall on civil engineering)
- marcosdumay 5y agoExplaining the asnwers in another way, yes, steel is necessary for both large horizontal openings without pillars and large vertical heights.