Hollowcore: What is it?
Hollowcore planks are precast concrete elements incorporating longitudinal voids or ‘cores’ through its length to reduce the self-weight and provide an efficient, lightweight section. High tensile reinforcement strands run longitudinally in the slab which are pre-stressed providing a slab which has an economic load/span ratio.
The hollowcore planks are nominally 1200mm wide, however, they can be cut to various widths to ensure economic coverage throughout a structure. Rhino Precast provide a comprehensive range of hollowcore planks from 100-500mm in depth.
Hollowcore: How is it made?
Hollowcore planks are pre-formed within a factory environment and can be manufactured by either slip form or extruding techniques. The manufacture process involves a machine tensioning the high tensile reinforcement strands and then extruding and compacting the concrete as it moves along the bed. The continuous slab is then cut to the required lengths.
Hollowcore: Where can it be used?
Hollowcore planks are suitable for use throughout the entire construction industry, whether that be within traditional masonry buildings, steel framed or concrete structures. They can be used within all building types including residential, commercial and industrial.
Hollowcore: The benefits
- Ease and Speed of Erection – Hollowcore planks can be hoisted into position on the supporting structure directly from the delivery vehicle. Time consuming activities such as propping, shuttering and concrete pouring are virtually eliminated. Upto 250-300m² can typically be installed a day.
- Sound Resistance – Hollowcore planks can be supplied with a mass of 300kg/m² for compliance with current building regulations Part E ‘Resistance to the passage of sound’. The robust detail eliminates the need for pre-completion testing.
- Fire Resistance – Hollowcore planks provide fire resistance without the need for additional treatment. This allows the planks to achieve a minimum 1 hour fire resistance as described within BS8110 and BE EN 1992-1-2.
- Large Spans – Pre-stressed units can be used to achieve large spans. This offers the designer flexibility and eliminates the need for intermediate supports. Please refer to our Span/Load Table or contact Rhino’s design team for further information.
- Immediate Working Platform – Once grouted, the completed floor becomes an immediate working platform for follow on trades, therefore, reducing site delay to a minimum.
- Flexibility in Design and Manufacture – Hollowcore planks can be manufactured with pre-formed holes or notches to allow for service penetrations reducing the requirement for on-site drilling. Rebated (chamfered) ends can also be provided during manufacture to allow slabs to bear into web of steel beams. Splayed (angled) cuts, solid areas and weep holes can also be provided where required by design.
Hollowcore: Technical Details
- Approved Document A – Pre-formed slots and rebated ends can be provided in hollowcore planks in order to satisfy Disproportionate collapse requirements in accordance with part A of the building regulations.
- Diaphragm Action – Once fully grouted, hollowcore planks provide a monolithic floor with full diaphragm action to the building.
- Camber – Due to the pre-stressing, all floor units will have an upward camber which should be allowed for in the finishes. Please contact Rhino’s design team for further information.
- Grouting – To ensure a ‘shear key’, the joints between the planks should be grouted with a minimum C30 grade concrete. A maximum 10mm aggregate should be utilised.