If an Employer has a contractor with a Contractor to demolish and rebuilt a site, does the Contractor have rights to sell the scrap materials from that site?
It depends what is said in the Works Information/Scope.
If the Contractor is required to simply demolish the building and leave the remains on site (which seems unlikely if construction of a new building is required) then the materials have to be left on site at wherever the WI/Scope says they are to be left.
If the Contractor is required to remove the remains of the old structure from site then, unless the WI/Scope specified what is to be done with them, it’s entirely up to the Contractor whether those remains go to landfill, are recycled, or are sold on for re-use.
In addition to Dave’s answer - I think it is worth noting the difference between wording in NEC3 and NEC4:
NEC3 73.2 - Contractor has title to materials from excavation and demolition only as stated in the Works Information
NEC4 73.2 - Contractor has title to materials from excavation and demolition unless the Scope says otherwise
I think the change is to make it clear if the Contractor is excavating material it is their problem to get rid of it under NEC4 and they could not be clever saying they did not price that. Whether scrap fits into that definition is the next question - which you would think would be part of demolition in most cases.
Either way, I think it should have been clarified at tender stage to avoid any issues on either side rather than trying to get clever in pricing.