The caisson shaft be 'dry' prior to concreting and the concrete shall
be poured in one continous operation through a hoper placed centrally over
each shaft and with trunking extending to within 1.5m of the concrete surface.
The size of the trunking shall be designed to suit the concrete slump in
order to flow and fill the caisson properly compacted by vibration pokers.
The concrete shall have a minimum cement content of 300kg/m3 and
a slump of not exceeding 150mm.
If the concrete caisson shaft is placed in 'wet', tremie pipe method
shall be used. The concrete shall be grade 40D with a minimum cement content
of 400kg/m3 amd minimum slump of 150mm.
All reinforcement shall be hot rolled deformed bars with a guaranteed
yield stress of not less than 425N/mm2 except where prefixed
'R' on the drawings. Prefix 'R' denotes mild steel with a guaranteed stress
of not less than 250N/mm2.
All laps in vertical reinforcement shall be a minmum of 46 bar diameter.
concrete cover to reinforcement, including links and stirrups, shall be
50mm.
