Could someone please tell me the origin of columns of the Pantheon of Rome?
I think the columns are of a stone/concrete composition, and the roof is concrete of sorts (but lime rather than cement based) with some void formation. This is ‘natural concrete’ – rubble for aggregate (included lightweight stone and bricks) with fines bound in a matrix. Not dissimilar to what we would describe as mass concrete, today The Romans would not have known reinforced concrete as they did not have steel. The columns act in compression so there would be little advantage in any reinforcement. A slide of it is here where you can see there is clearly no tensile component in the design.
