A Swedish study embraced preliminary tests at the form manufacturer's factory and full-scale tests in connection with the production of concrete structures for 13 one-family houses. The vibrator manufacturer also took part in the project. The tunnel form used for these residences provided for two walls and the floor slab supported on them. The form was set in place on the previously cast level floor slab. After casting and hardening of the first level of concrete, patented "shrink" devices in the floor form and at the lower part of the walls permitted loosening the form in order to lift it away. A loader with special fork attachments then lifted the elements into place on the second story of the houses.
Concrete used had a compressive strength of approximately 4350 psi. It was made with 5/8-inch maximum aggregate and 500 pounds of cement per cubic yard. Slump ranged from 8 « to 9 « inches. Formwork vibration alone gave satisfactory results with superplasticized concrete relative to the requirements of strength, homogeneity, formwork filling and casting around reinforcement. Although the concrete for walls and floor structure was cast continuously in less than 1 hour, no visible settlement cracks occurred in the joint between wall and floor.
Formwork vibration of superplasticized concrete resulted in a slight increase of surface porosity on the walls as compared with conventional immersion vibration. There were more bug holes, particularly those smaller than 3/16 inch in diameter but these were noticeably shallower than with immersion vibration. The results show that the method of filling wall forms entirely before vibration is a suitable one. When using superplastized concrete with a slump of at least 8 inches, formwork vibration is sufficient to level the top surface to such a degree that planing with a power trowel can be carried out without previous surface vibration.