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Is Concrete Doomed to Fail?

allen griggsallen griggs Member Posts: 35,695 ✭✭✭✭
edited May 2017 in General Discussion
I was watching one of these shows on the History Channel about Life After Humans.

They showed building crumbling a hundred years from now. Said that concrete will fail after a hundred years, the rebar will rust out and then it is Auf Wiedersehen for the concrete.

Is this for real? I just built an addition onto my log cabin and I would like for it to last more than 100 years. The foundation footings are concrete, buried underground, they are 24 inches wide and 12 inces thick, with rebar. Will these footings fail in 100 years?
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Comments

  • WranglerWrangler Member Posts: 5,788 ✭
    edited November -1
    It's real... give or take a few decades. Depends on environmental and geological conditions for your region of the country and type of concrete.
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  • p3skykingp3skyking Member Posts: 23,916 ✭✭✭
    edited November -1
    Concrete takes 100 years to completely cure.
    The next hundred years is devoted to decomposing.

    You'll get about 150-175 good years out of it.
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  • gruntledgruntled Member Posts: 8,218 ✭✭
    edited November -1
    How long are you expecting to live?
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  • allen griggsallen griggs Member Posts: 35,695 ✭✭✭✭
    edited November -1
    Damn, that ain't right.
    I have a book on old time building techniques. It shows a house foundation where they dug a trench and filled the trench with big rocks and boulders etc.

    That seems primitive but since those rocks are already 4 million years old, looks like they will outlive my concrete.

    Why does the concrete go bad?

    I have seen a documentary on the Romans, they had concrete that would set underwater. It looked like some of those jetties, 2,000 years old, were still in pretty good shape.
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  • kidthatsirishkidthatsirish Member Posts: 6,984 ✭✭✭
    edited November -1
    Yeah Roman concrete is pretty awesome stuff...i wish our modern stuff was just as good.
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  • oldWinchesterfanoldWinchesterfan Member Posts: 1,050 ✭✭✭
    edited November -1
    Words from a wise friend of mine. There are three things you always know about concrete.

    1. It will get hard
    2. It will crack
    3. Nobody's gonna steal it
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  • Ditch-RunnerDitch-Runner Member Posts: 25,382 ✭✭✭✭
    edited November -1
    look at the hoover dam or what ever they call it now and countless other dams and RR bridges one the big 4 bridge in the town I grew up in I know it closing in on 100 years old
    I am sure they get cracks and flaking but it failed in 100 years there is going to be a world of hurt on a lot of people

    link to a old article some may find it interesting
    http://www.shelbycountyhistory.org/schs/archives/landmarks/big4landmarka.htm
    it s no trespassing area and has a trap door about half way across you climb down inside the big arches ( I had a young lady many years ago 1974 or so show me the way in more ways than just the trap door [:D][:D])
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  • shilowarshilowar Member Posts: 38,811 ✭✭✭
    edited November -1
    Well it is powder mixed with stone and water. I'd think after it cures enough it will eventually turn back to powder, especially if it I sustaining the pressure of weight for decades.
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  • Colonel PlinkColonel Plink Member Posts: 16,460
    edited November -1
    quote:Originally posted by kidthatsirish
    Yeah Roman concrete is pretty awesome stuff...i wish our modern stuff was just as good.

    I watched a show on Roman construction. Their take was that Roman Concrete is still standing because the Romans understood that iron rusts and would weaken the structure.
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  • 320090T320090T Member Posts: 2,715 ✭✭✭✭✭
    edited November -1
    Lots of concrete fails not because of the concrete but because of the re-bar or wire in it. Rust expands and busts apart the mixture. Notice the new style re-bar grids going in new interstate construction? Coated not to rust.
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  • grumpygygrumpygy Member Posts: 48,464 ✭✭✭
    edited November -1
    Depends on how good the folks were that were mixing it. Lane Community college was Built in 1968 and is flat falling apart huge chunks of concrete are falling off the buildings.
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  • droptopdroptop Member Posts: 8,363 ✭✭
    edited November -1
    quote:Originally posted by Ditch-Runner
    look at the hoover dam or what ever they call it now and countless other dams and RR bridges one the big 4 bridge in the town I grew up in I know it closing in on 100 years old
    I am sure they get cracks and flaking but it failed in 100 years there is going to be a world of hurt on a lot of people

    link to a old article some may find it interesting
    http://www.shelbycountyhistory.org/schs/archives/landmarks/big4landmarka.htm
    it s no trespassing area and has a trap door about half way across you climb down inside the big arches ( I had a young lady many years ago 1974 or so show me the way in more ways than just the trap door [:D][:D])


    Actually, modern day concrete mixes are as strong or stronger than historic concrete mixes. ... So, why do modern structures not last as long? ... e.g. The Hoover Dam was built to last 2,000 years---the concrete won't fully harden for 500 years.

    https://www.quora.com/How-long-are-our-current-day-concrete-structures-designed-to-last
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  • gearheaddadgearheaddad Member Posts: 15,091 ✭✭✭
    edited November -1
    quote:Originally posted by oldWinchesterfan
    Words from a wise friend of mine. There are three things you always know about concrete.

    1. It will get hard
    2. It will crack
    3. Nobody's gonna steal it


    Yup. This is what I too know about concrete.[:D]

    About the only 3 things a good concrete Man will guarantee about concrete.[;)]
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  • JamesRKJamesRK Member Posts: 25,670 ✭✭✭
    edited November -1
    I'm no expert on concrete but I know enough not to believe anything I see on the History Channel. Some of it is entertaining and some of it has some truth in it, but you shouldn't take any of it as gospel.

    The same channel tells me concrete will last forever and it will collapse in a hundred years. Both can't be true. Which one do I believe? They are probably both wrong.
    The road to hell is paved with COMPROMISE.
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  • mogley98mogley98 Member Posts: 18,291 ✭✭✭✭
    edited November -1
    Wonder what they made all them castles out of? They seem to last forever :)
    Why don't we go to school and work on the weekends and take the week off!
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  • rossowmnrossowmn Member Posts: 1,959 ✭✭✭
    edited November -1
    I once had a student whose father was a concrete contractor. He said his dad always said there are only two kinds of concrete: concrete that has cracked, and concrete that hasn't cracked yet. Sooner or later, moisture will find a way in, and then it's just a matter of time (years or decades or centuries, but inevitable).
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  • BrookwoodBrookwood Member, Moderator Posts: 13,768 ******
    edited November -1
    I have noticed that man made structures fail when they are not lived in aka abandoned.
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  • JunkballerJunkballer Member Posts: 9,311 ✭✭✭✭
    edited November -1
    Check out some old abandoned military air bases with concrete runways, even growing weeds and grass can destroy them in a few years from neglect as you will see.

    "Never do wrong to make a friend----or to keep one".....Robert E. Lee

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  • rambo rebelrambo rebel Member Posts: 4,028
    edited November -1
    God made the rock and man makes the concrete.

    unless you seal it, concrete will absorb water. water molecules will break down anything that it can penetrate.

    faster in cold climates. concrete absorbs water, temp drops to freezing and if it stays below freezing long enough those absorbed water molecules freeze and expand, breaking apart the concrete.


    try this experiment. take a small 5-10 pound chunk of concrete and put it in the oven and bake it on the lowest temp you can for several (2-3) hours. take it out and weigh it on some good scales. them take it outside when the humidity is high for a couple days and then weigh it again. it will weigh more than when you took it out of the oven. don't let the rain get to it. it will suck moisture out of the air. ever wonder why a bag of cement gets hard in humid climates even if it's in the "dry"?
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