Just read in “Discover” magazine about a new concrete developed by the University of Michigan and used in Japan’s Mihara Bridge. It uses polyvinyl alcohol fibers and extremely fine silica sand. It is three times more expensive than ordinary concrete, but is 500 times more flexible. It supposedly withstands earthquakes and need less reinforcing steel. It is less likely to crack, lighter and longer lasting than regular concrete. Now Cloud’s dome-structures could withstand just about anything!
Also of note, in “National Review”, someone told Wm. F. Buckley that he used the word “cement” when he meant “concrete”–so those of you out there who have made that mistake can count yourself in at least well-educated company!
(Of course, I once read that a scientist discovered a new concrete when he spilled the beer he just happened to have in the lab into the concrete he was mixing up and the result was lighter and more dense than regular concrete! Since density is weight per unit volume I never quite understood how it could be both lighter and more dense, but hey, I never understood what he was doing with beer in the lab either.)
Replies
Well, I just ran across a post in another forum that stated that baking soda could be used to accelerate the curing time of thinset.
It caused me to wonder how that was discovered.
baking soda could be used to accelerate the curing time of thinset.
It caused me to wonder how that was discovered.
I think that was discovered by my sister...
you should try one of her cookies sometime...
ROTFLMAO!
I've told the story here about one of my brother's homemade bagels.....a true weapon!
>I never quite understood how it could be both lighter and more dense
He used lite beer...makes it lighter and ya gotta be dense to drink it...???
###
As for use in thin-shell structures, I'd guess the flexibility compromises the compressive strength, and that ain't so good for us. The real strength of a dome comes from it normally being entirely in compression.
As to pva fibers replacing rebar in our application, boy wouldn't that be nice. It'd save our biggest labor component and knock quite a few $/sf off the base price. However.......it has yet to work. We need the reinforcing oriented in a specific direction to provide predictable tensile strength at predictable places. But fibers orient themselves at random, plus the amt remaining in the wall with the shotcrete process, and not lost to rebounding, is a bit imprecise. There are differing opinions among the pva suppliers and the thin-shell engineers. I thought I had a true debate planned among one of each--I envisioned it as a steel-cage match neither could leave till they reached agreement--but the pva guy chickened out...ummmm...I mean he got delayed on a project in Mexico and missed his flight. Darn, that coulda been fun.
Too bad there isn't a way to orient the strands like they do with OSB. Or when they spray on flocking--put a charge on the thing and a charge on the gun. I suppose all the water in the mix pretty much ruins the static charge thing.
Like your idea of the debate in tha cage--maybe that would work for the Tavern discussions here? In this corner, with the nailgun is Methmonster. In the other corner, with the chainsaw is Lil Bo Peep....
Must have been light beer. Enough light beer will make me even more dense.
Light beer makes me light headed.