The sports block will include a sports hall with 12 badminton courts, a 25 m swimming pool, an indoor cricket centre and a 12 m high climbing wall.
The scheme will form part of the university's new 12 ha de Havilland campus near Hatfield, which will merge its Watford and Hertford campuses.
Carillion's special projects division will build the facilites and the firm's services arm will operate them for the 30-year contract.
The consortium comprises the Royal Bank of Scotland and architects Austin-Smith:Lord and TPS Consult.
Carillion has now financially closed 16 PFI projects, 11 of which are operational.