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A comment on Rubber concrete that self-seals and is cheaper and more environmentally friendly. Parent comment

Re:Rubber concrete that self-seals and is cheaper and more e... by marcusverus on Sunday November 03, 2019 @09:58PM (#21438643)
Two issues: 1) unequal dispersion of the balls could create super weak spots that are mostly empty space. I'm not sure how engineers could use a material where the structural integrity isn't consistent. 2) If water ever penetrated the swiss-cheesyness of the concrete in freezing weather, you'd be in big trouble.
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Re:Rubber concrete that self-seals and is cheaper and more e... by disillusioned on Sunday November 03, 2019 @10:34PM (#21438823)
Yeah, this is already a nightmare with rebar in reinforced concrete. Just imagine actual ping pong ball sized voids filling with moisture. Swiss cheese, indeed.
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Re:Rubber concrete that self-seals and is cheaper and more e... by galaxyLogic on Wednesday November 06, 2019 @10:51PM (#21470245)
But it wouldn't be holes, it would be water-tight ping-pong balls.
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Re:Rubber concrete that self-seals and is cheaper and more e... by BurningFrog on Sunday November 03, 2019 @10:58PM (#21438912)
OK, what if you carefully place the balls in a regular pattern?
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Re:Rubber concrete that self-seals and is cheaper and more e... by beerandt on Monday November 04, 2019 @09:51AM (#21442132)
Imagine placing ping pong balls in a regular pattern in the bottom of an empty swimming pool, then filling it up with water.
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Re:Rubber concrete that self-seals and is cheaper and more e... by BurningFrog on Monday November 04, 2019 @10:58AM (#21442789)
You'd have to secure them in place. Perhaps with a metal grid.
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Re:Rubber concrete that self-seals and is cheaper and more e... by beerandt on Monday November 04, 2019 @03:52PM (#21446386)
Sure it's doable, it just makes the task that much more difficult. Plus you need to ensure there are no unintentional voids from the balls blocking the pour. Code requires that they can't be within 1-2 inches of any steel or the surface of the concrete.

Also, most designs assume a uniform cross section, and changing that greatly complicates the design method.

And remember that the laborers doing this don't always understand (or care) about these sort of restrictions.

It's usually cheaper and less risky to just use a lightweight mix, with injected air, if needed.

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