[decimon]

Caption: X-ray microtomograph (left) shows pores (blue) that remain within lightweight aggregates (LWAs) after water has migrated from the pre-wetted materials during the first day of hydration. In the two-dimensional image (right), the emptied pores are superimposed over the original microstructure (hydrating cement paste is white, sand is light grey, and LWA is dark grey), illustrating the detailed pore structure of LWA particles.

Credit: NIST

Usage Restrictions: None

[decimon]

Don’t ask why ping.

I guess that Hadrian’s boys didn’t need to know why to know what worked.

[massgopguy]

That's right. My Italian ancestors invented concrete. We made things out of it. Aqueducts, Coliseums.......shoes

[Harpo Speaks]

Reardon Concrete?

[fso301]

So, you essentially take a ground, highly porous material, saturate it with water and use it as a portion of the fines?

[WOBBLY BOB]

MN-DOT should hire Romans to build our bridges.

[JRios1968]

One of the reasons concrete plants try to keep their aggregate stocks wet to the SSD (saturated, surface-dry) condition. The key, though, is knowing how much water content the aggregate has, because it has to be accounted for in the mix design.

[bert]

",img src="http://www.engr.ncsu.edu/news/media/images/canoe80a.jpg">

NC State Concrete canoe in competition

[AFreeBird]

So in other words; if you build it right the first time, even if it costs a little more, it holds up better.

Hmmm.... Who would have thunk it.

[wildbill]

I think it is a mistake to take the knowledge of the Roman engineers lightly and assume they used this special lightweight concrete by accident.

They built many specialized projects out of concrete using various techniques that could be used today. I remember one article on FR about the way they built a harbor in the eastern Med by setting down forms under the sea to build concrete piers. I think they were ‘internal cured’ concrete as well.

Then there are their acqueducts with concreted tunnels and pipes that had to have very precise ‘drops’ to harness gravity to move the water while still keeping the flow under control.

Once the Roman engineers were gone, the world lost the formula for concrete for a millenia.