flexible while you’re making something, utterly inflexible once it’s made. In the hands of an architect or a structural engineer, concrete is a remarkable material – you can pour it into a mould, and set it to be slim and stiff and strong in almost any shape you like. It can be dyed, or grey; it can be rough or polished smooth like marble. But the moment the building is finished, the flexibility ends: cured concrete is a stubborn, unyielding material.
