Traditionally RC Cores construction has been generally limited to a choice between jumpform platforms and slipforming techniques. With slipform in city centres generally restricted to 10 hour shifts (lift on and lift off) the obvious speed advantage is diminished. Placing of embed plates for structural steel connections, box outs and services has also been inaccurate at times using these techniques.

John Doyle Construction took on these challenges to innovate a new way to construct medium to small size cores to encompass the speed of slipform, the safety of guided jumpform, with the dimensional accuracy workmanship standards of offsite construction.

Additional innovation benefits from this technique have been developed giving real time construction of floors, landings and stairs within the storey cycle time, direct and safe access to all the embed plates for fin plate welding and access for service riser installation during core construction.
 

Key Innovations using Twin Wall Hybrid RC Cores by John Doyle Construction at More London 7:
 

• Core twin walls made with embed plates, lift fronts, lift inserts, lighting boxes, cast in factory conditions.
• Self compacting concrete producing concrete strengths of 30N in 24 hours.
• No formwork obstructions so internal floors, landings and pc stairs completed with each floor, enabling safe access and instant snagging.
• Separate access for welders to fin plate connections taking them off critical path.
• Core construction speeds of average 3 day cycle inclusive of floors etc.
  Note: 7 storeys on Core A achieved 2 days/cycle.
• Highly accurate core dimensional controls - worst case 9mm over 13 stories.
• Cores completed, snagged and clear, including lift roof slabs 2 days after core completed.
• Cores can be constructed adjacent to party walls and obstructions.
• Cores can be made waterproof by using Calcite concrete.