On: Why was Roman concrete so durable?

[LegitShady]

> The rust is essential to bind it to the cement. Without, it adds little strength.

Do you have a citation for this? As far as I know this is entirely not true.

Rust is an expansionary product - when steel rusts its volume increases something like 10x, which reduces the connection between the concrete and the steel and causes issues like cracking and spalling. Minimizing rust improves the long term performance of rebar.

[moloch-hai → LegitShady]

They leave the rebar out to rust a bit, on purpose, before they pour. Surface rust is good, but more is bad. Like many things in life.

[zoklet-enjoyer → moloch-hai]

I read your comment as I finished eating my third slice of pie and wondering why I cut myself 3 slices.

[moloch-hai → zoklet-enjoyer]

You could have cut one big slice instead.

[PakG1 → zoklet-enjoyer]

3 is the limit. More than 3 is bad.

[aborsu → PakG1]

One would think the limit for pie is closer to 3.14159265359

[PakG1 → aborsu]

It is, but it's not easy to cut pi slices of pie without being unfair to others who want to have equal slices of pie. Plus, the effort to be so exact may not be worth the utility. You may hit the true pi limit by random luck too.

[imron → zoklet-enjoyer]

Perhaps you’re just mathematically inclined.

[IgorPartola → LegitShady]

Rust is perfect. We don’t criticize rust on HN.