3 ms·

It's probably not replacing the cement though -- it's almost certainly an additive in the concrete mixture, like flyash. And even if it does make the mixture st

It's probably not replacing the cement though -- it's almost certainly an additive in the concrete mixture, like flyash. And even if it does make the mixture stronger, there are lots of variables for that, like aggregate strength, water/cement ratio, curing times, temperatures, additives and admixtures. Glossary for the people here who haven't taken classes from people really particular about it: * Cement is the 'glue' part * Concrete is Cement + small aggregate (sand) + large aggregate (gravel) * Cement doesn't dry, it cures, and the water becomes bound in gels between the cementitious minerals. If it does dry out (due to fire, or prior to curing), it loses its strength. * The trucks aren't cement mixers, they're concrete mixers.

mcpackieh 3y ago
> It's probably not replacing the cement though -- it's almost certainly an additive in the concrete mixture, like flyash. Fly ash is pozzolanic, it can be used to replace 30% or more of the cement in concrete.
kibibu 3y ago
> It's probably not replacing the cement though -- it's almost certainly an additive in the concrete mixture, like flyash. No probably about it. The article says it can replace some portion of the sand usually used in making concrete
- civilitty 3y ago
  No one told me that we’re reading the article now. That sets a terrible precedent!
PaulDavisThe1st 3y ago
Cool OT sidenote about this. I live in an adobe house, and I wondered for a long time what the difference is between concrete blocks and adobe bricks, in terms of their physico-chemical structure. Adobe has comparable compressive strength to concrete blocks, but unlike concrete will dissolve in water. I always found this a bit mysterious. Turns out that the most significant difference is that in concrete (or any cementitious material), the important molecular bonds are covalent. In adobe the bonds are ionic. Consequently, adding water to adobe easily disrupts the structure by interfering with the ionic bonds (just as it when salt dissolves in), but does essentially nothing to the covalent bonds in concrete. Even cooler, perhaps, is that as the wet adobe dries out again, the same bonds will reform, and you get back to the original state again.

mcpackieh 3y ago

> It's probably not replacing the cement though -- it's almost certainly an additive in the concrete mixture, like flyash. Fly ash is pozzolanic, it can be used to replace 30% or more of the cement in concrete.

kibibu 3y ago

> It's probably not replacing the cement though -- it's almost certainly an additive in the concrete mixture, like flyash. No probably about it. The article says it can replace some portion of the sand usually used in making concrete

civilitty 3y ago
No one told me that we’re reading the article now. That sets a terrible precedent!

PaulDavisThe1st 3y ago

Cool OT sidenote about this. I live in an adobe house, and I wondered for a long time what the difference is between concrete blocks and adobe bricks, in terms of their physico-chemical structure. Adobe has comparable compressive strength to concrete blocks, but unlike concrete will dissolve in water. I always found this a bit mysterious. Turns out that the most significant difference is that in concrete (or any cementitious material), the important molecular bonds are covalent. In adobe the bonds are ionic. Consequently, adding water to adobe easily disrupts the structure by interfering with the ionic bonds (just as it when salt dissolves in), but does essentially nothing to the covalent bonds in concrete. Even cooler, perhaps, is that as the wet adobe dries out again, the same bonds will reform, and you get back to the original state again.