Flexicore

Hollow-core is a type of precast, prestressed concrete floor slab. It is often used in construction of multi-storey buildings. The advantages it has over cast-in-place concrete floor are that it is lighter in weight and often cheaper. Also, wet concrete needs to be pumped or carried up to higher floors. The slabs which are manufactured off site are simply lifted with a crane and set in place. Disadvantages are an increased overall floor thickness (due to the requirement of steel supporting beams), the cost of a steel frame over the cost of concrete columns and increased cranage requirements.