Civil Engineering March 2021 | Vol 29 No 2

28 March 2021 Civil Engineering faster to construct with an optimal load capacity to weight ratio for a concrete slab solution over this span. Below the superstructure, a standard concrete surface bed with typical joints on compacted fill was designed for all ground floor slabs. The superstructure was supported off deep piled foundations – cast in situ reinforced concrete augured piles with reinforced pile caps and ground beams. The RC ground beams along the eastern and western façade between supporting piles on grid acted both as the vertical support of the façade brickwork and the horizontal restraint via passive earth pressure to resist the base horizontal thrust of the roof. The pile sizes ranged from 450 mm to 600 mm in diameter. CONSTRUCTION The piling work was carried out by Pilecon using 25 MPa ready- mix concrete supplied by Metier Mixed Concrete. The piles ranged in depth from 4 m to over 15 m, and the 40 piles were cast in eight days during August 2019. The waterproof reinforced concrete shells for the two swim- ming pools were constructed by the main contractor Akhane Construction using an approved Penetron joint applicator between October 2019 and August 2020. The extended construc- tion period was due to two factors: the forced Covid-19 lockdown period and staggered construction times to allow for other critical construction works within the confined site. WDI completed the finishing on the pools, including all filtration and cleaning systems, by November 2020 and the pools were filled and com- missioned in December 2020. The eastern portal frame and western columns supporting the feature roof were workshopped and Akhane Construction proposed that each set of east and west elements be cast together and in one lift each. The western column was a standard lift of 8 m, but the eastern portal required both columns, the roof beam, and the extending cantilever beam to be cast in one. Both east and west elements required the fixing and accurate setting of the Peikko cast-in anchors to allow for the port structural steelwork erection. Form-Scaff was appointed as the specialist formwork supplier for these elements and produced customed-made steel shutters in accordance with the project requirements. The formwork allowed for accurate setting out and fixing of the Peikko anchors with pre-drilled end plates which enabled the anchors to be set in position and bolted to the plate. In addition, the formwork at eaves beam level had openings to allow for the transverse portal beam cast-in reinforcement to protrude and be cast with the associated element. The concrete mix design was altered slightly to be a 13 mm aggregate 50 MPa mix. The reduction in aggregate size was done to assist with the highly congested reinforced zones and in producing a high quality special smooth finish. Compaction was done via two extended length poker vibrators using a controlled pour rate. The first set of feature roof supporting elements was cast in October 2019, with the ninth and final set cast successfully in December 2019. This allowed sufficient time for the planned plate girder installation to occur over two days in mid-January 2020. The hollowcore planks for the first floor of the eastern block were delivered and erected on site over two days in early February 2020. The planks supplied by Concrete Slab Supplies (CSS) for the project were: Aerial progress photo prior to the Covid-19 lockdown (courtesy of The Structural Workshop)