[Secret Agent Man]

I thought we had figured out the romans formula for concrete.

[Husker24]

Yes, the Romans used the volcanic ash they were talking about.

[RedWulf]

We did, but the stuff is impossible to break down without explosives so it’s not used much. We like build and then rebuilding to much.

[Jonty30]

They used a volcanic ash that you cannot get just anywhere. The goal is to find a common binding agent that can be used all the time.

[trebb]

I thought we had figured out the romans formula for concrete.

Same here - wonder if the show was rigged to make it seem better than advertised.

[cloudmountain]

LOL; we did figure it out:
the basic mixture of mortar can be made using the volume proportions of 1 water : 2 cement : 3 sand. Most of the student activities can be conducted using this basic mixture. Another "old rule of thumb" for mixing concrete is 1 cement : 2 sand : 3 gravel by volume. [Google]

[GOPJ]

As Buyukozturk describes it, the “mesoscale” represents the connection between microscale structures and macroscale properties. For instance, how does cement’s microscopic arrangement affect the overall strength and durability of a tall building or a long bridge?

Microscale reinforcing rods? Great... and when the structure needs to be torn down and replaced>.. what then?