The centring is normally made of wood which was a relatively straightforward structure in a simple arch or vault but with more complex shapes clay or sand bound by a weak lime mortar mix could be used.
a vast superstructure of centralized control
a vast superstructure of centralized control
The centring is normally made of wood which was a relatively straightforward structure in a simple arch or vault but with more complex shapes clay or sand bound by a weak lime mortar mix could be used.