Exterior walls up to 50 feet high were cast in place to their full height with single placements during construction of an unusual sculptured building for the 98th Street Racquet and Swim club in Bloomington, Minnesota. Tilt-up construction had been studied but wall sections were considered to be too large to make tilt-up practical. Tilt-up walls would also have required frequent vertical joints; continuous casting saved fussing with joints between placements of separate sections of wall. An aluminum forming system was chosen which had rigid components that required a minimum amount of splicing and ensured that the walls would be produced straight and plumb. The system provided for the form design strength needed while keeping the forms light for easy handling.
The series of large single placements used produced the best construction sequencing and minimized the rebracing task. Each long side wall one of which is 332 feet couldn't tie into perpendicular walls, interior slabs or decks until later in the work sequence. Thus the forms, and later the walls, needed bracing until additional construction was completed.
Concrete crews used a large truck-mounted concrete pump, hydraulic boom and concrete hose to deliver the mix all the way into the bottom of the wall forms. The structural wall thickness is 12 inches, plus 2 3/8 inches on each side for areas between rustications. Concrete was placed continuously in 2-foot lifts at a carefully controlled rate and thoroughly vibrated with a high-cycle internal vibrator. Using the tall forms and monolithic placement saved time, labor and form reanchoring costs. Crews averaged one placement a week for the 47-foot-wide wall sections. The contractor could concrete a section in one day. The job was planned for stripping and moving both forms and scaffolding in a single day; thus a crane and the concrete pump unit were tied up only one day per week.
