Disruption
Loss of productivity — the same work taking more hours than it should have — caused by interference with the planned way of working. Distinct from delay: a project can be disrupted without being late, and expensively so.
Delay is about the completion date. Disruption is about efficiency, and it is quite possible to finish on time while having been disrupted throughout, by accelerating and by throwing labour at the problem. That extra labour is the loss, and it is recoverable — if it can be proved.
The strongest way to prove it is the measured mile: compare a period of your own unimpacted work against the same work while impacted, using the project as its own control. It is persuasive precisely because it does not rely on a theoretical productivity norm the other side can dispute. It relies on what your crews actually achieved — which requires that somebody was recording installed quantities and allocated hours at the time.