Concrete's Greatest Weakness is Time

Comments · 1.2K

• PR

  @PracticalEngineeringChannel · 10 months ago · pinned

  🏞Lots of cool stuff (plus my book) available at the PE store: <a href="https://store.practical.engineering/">https://store.practical.engineering/ </a><br>🌌Get Nebula using my link for 40% off an annual subscription: <a href="https://go.nebula.tv/Practical-Engineering">https://go.nebula.tv/Practical-Engineering</a>

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• XA

  @xani666 · 10 months ago

  little Grady needs a little yellow vest, OSHA might compain

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• NE

  @neilwinkelmann8540 · 10 months ago

  Concrete&apos;s greatest weakness is arguably corruption. Bribes to do a lesser job. Less cement, lower standards of placement, inadequate compaction, water added to increase working time, missing reinforcement, falsified test results. It happens.

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• KE

  @keilanl1784 · 10 months ago

  Last time I was this early, the concrete hadn&apos;t cured yet.

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• SC

  @ScoutSniper3124 · 10 months ago

  I worked at a pool company where they had Redi-Mix trucks which mixed the concrete up in the truck at the site not at the plant. <br>All went well until the Operations Manager changed the mixture ratios to &quot;Save Money&quot; by skimping on cement and aggregate. Dozens of pools were poured and finished and within a short period of time began to FAIL. A very expensive engineering firm was hired to troubleshoot the problem, and when they found his handwritten notes to the job site workers to change the ratios it was the &quot;smoking gun&quot; which left him immediately jobless.

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• VE

  @VenerableBede9106 · 10 months ago

  <a href="https://www.youtube.com/watch?v=f2uad6LT9fo&amp;t=586">9:46</a> I watched a film called 28 Day Later to learn more about this. Unfortunately, it turns out there is no cure.

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• PS

  @psmirage8584 · 10 months ago

  I used to work as a concrete field tester back in the early 1990s. &nbsp;I saw all kinds of things. &nbsp;One of the big factors was the contractor doing the placing. &nbsp;Some of them were lazy, and would ask the delivery drivers to &quot;soup it up&quot; - add lots of water so they didn&apos;t have to shovel the concrete into back corners. &nbsp;This was particularly bad for basement pads and foundations. &nbsp;My job was to test the concrete slump. &nbsp;Usually, the specification was for 80 to 100 millimeters, but sometimes contractors would tell the driver to soup it up to 160 or even 180 millimeters. &nbsp;If I caught them doing this, I could order the pour be stopped until dispatch was notified. &nbsp;More than once, they ordered the driver back to the plant with their load - at the time worth $600-$700, to basically dispose of it. &nbsp;If that happened one too many times, the driver was dismissed.

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• IA

  @IanHutchison · 10 months ago

  You&apos;re telling me &quot;28 Days Later&quot; isn&apos;t a documentary on concrete science?

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• JA

  @JackRussell021 · 10 months ago

  I had to laugh at the mention of &quot;square smoot&quot; as unit of area.

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• DT

  @DT_02496 · 10 months ago

  It was exactly 11 months ago that I suggested to use &quot;gradys&quot; as units of weight. Some smart people replied and suggested &quot;kilogradys&quot;. Im strangely delighted and proud to now hear you actually use these units that your viewers came up with. Thank you!

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• AC

  @AcidburnHckr · 10 months ago

  A note on field cured samples. They are often not a good representation of the final product either. The samples are cured in 4&quot;x8&quot; or 6&quot;x12&quot; cylindrical molds which do not share the same temperature and hydration conditions that are present in the final product. This causes field cured samples to often break well below design strength due to not having access to moisture in the air and being exposed to wind and sun which affect large volumes of concrete vastly less than small concrete cylinders. Not to mention the molds are made of plastic which also completely changes the way that the samples cure. The closest thing you can get to definitive strength measurements on a placed concrete product is destructive testing such as Windsor probes and even those have their issues. I spent 10 years as an ACI certified concrete field testing technician and I worked in a lab breaking cylinders so I have seen the headaches that field cured samples tend to cause projects.

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• BW

  @bwedesign · 10 months ago

  In more than 25 years as an architect, I only had to order one slab removed because it wasn&apos;t coming up to strength. &nbsp;Nearly 20 years ago, I did a fire station addition / renovation with a concrete apron between the building and street. &nbsp;There was one 25 foot section that didn&apos;t come to strength in 28 days - and if I remember correctly was supposed to be high-early strength. &nbsp;The fire department wasn&apos;t happy, because it was directly in front of one of their existing truck bays, but it had to be ripped out and repoured.

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