[GSlob]

The dressing could not be soft cast chalk- with the blowing sand from the desert next door it would be eroded away in a nick of time. If anything, the pyramid exterior needed to have been made of the hardest materials available, for the whole point of having a pyramid is its extreme durability. To cast the pyramid interior [the bulk of its volume] would take a lot. And allowing the soft castings to settle and harden to the depth of the pyramid dimension would take longer than the whole reign.

[GoLightly]

My point had to do with a reduced need for the quantities of kilned lime you had assumed, at which point we're not talking soft cast chalk, but a form of concrete.

[elli1]

Did you read the article?

The theory is that limestone concrete (limestone slurry mixed with lime from ash and salt) was used near the top of the pyramids. The pyramids were covered with a veneer of limestone slabs originally, IIRC, and are long gone. Recycled into other stuff.