In 1963 I was involved in the detailed design of an extension to the contact tank at the then Coventry Water Undertaking's Strensham Treatment Works.
In order to speed construction the columns were precast concrete set in pockets in the floor slab.
These columns were temporarily propped during the erection of the prestressed concrete roof beams and slabs.
Following the completion of erection of the precast structure an in situ reinforced concrete topping was placed to seal the roof structure.
The precast column pockets were filled with concrete to complete the roof structure. This approach saved time and cost in 1963.
RICHARD PERRY (M), firstname.lastname@example.org