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Thread: AASHTO Load and Resistance Factor Design (LRFD) bridge specs

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    Cyburbian Jeff's avatar
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    AASHTO Load and Resistance Factor Design (LRFD) bridge specs

    Anyone have this that wouldnt mind looking something up for me?

    I'm just not finding this online, and I'm not buying this book.

    Looking for min/max air content of cement used for bridge decks.

    Gracias!

  2. #2
    Cyburbian
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    IDOT uses 5-8%

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    Cyburbian Jeff's avatar
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    Whoa, thats a wide range. Is that range subject based on the compressive strength of the concrete?

    Every 1% air increases/decreases F'c ~500 psi.

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    Cyburbian
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    4000 psi @ 14 days

  5. #5
    Cyburbian Jeff's avatar
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    Hmmm....

    First off...What State does the "I" stand for.

    Why 14 days? Cocnrete doesnt reach its full compressive strength until 28 days?

  6. #6
    Cyburbian
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    Quote Originally posted by Jeff View post
    Hmmm....

    First off...What State does the "I" stand for.

    Why 14 days? Cocnrete doesnt reach its full compressive strength until 28 days?
    Illinois, and I was surprised to see 14 days as well. It used to be 28 days, I thought is must have changed with the 2007 spec book, but I just checked the last 2002 and it was 14 days as well. Contractors on my jobs have had it easy since I rarely take a 14 day test. Guess I better change that.
    Here's their spec book Section 1020 is PCC

    Concrete will continue to gain strength in lab conditions forever. If you plot your results you will get a parobolic curve. So requiring 4000 psi at 14 days is like requiring +/-5000 at 28 days.

  7. #7
    Cyburbia Administrator Dan's avatar
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    Moderator note:
    Just a friendly reminder to eschew obfuscation, and spell out acronyms that are infrequently used by most planners in thread titles. Changed "LRFD" to "Load and Resistance Factor Design" in the thread title. Thanks!

  8. #8
    Cyburbian Jeff's avatar
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    6% in the snow belt (freeze/thaw/deicing salts) for those that care. Disscussions of upping it to 8% at PaDOT now.

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