CITY BUILDS AFRICA’S FIRST PRECAST CONCRETE WATER TOWER PART 3

Caption: Resting on bearing pads, the 12 tapered beams will carry and distribute the load of the precast-concrete tank and its contents.

This is Part 3 of a three-part series.

His team is supported by a state-of-the-art 150 t mobile crane, which has the capacity to lift the heavy precast-concrete elements and reach to efficiently place them. The 12 tapered beams, for example, each weigh a staggering 18,5 t and the columns for the second and third rotations slightly less.

While the tank is significantly smaller than the reservoirs that Van Rooyen and his team have already built, constructing it many metres above ground poses unique challenges.

Safety of employees is on top of mind for RSMM Construction and Corestruc. Therefore, the companies have contracted the services of a specialist work at height safety consultant to assist with occupational health and safety protocol. It will also provide specialist training to the team.

Four sub-contractors who have been sourced from communities located within the construction footprint will work alongside Corestruc’s team to construct the floor slab. A total of 104m3 of concrete will be placed to construct the 350mm-thick floor slab. One of the challenges is the heavy reinforcement in the beam junctions. Therefore, the placement of concrete will have to be carefully managed to ensure that the correct compaction is achieved. This while also ensuring that the top portion of the cast-in-place shaft is water-tight.

An articulated boom lift has already been placed on top of the superstructure to assist with the installation, as well as the grouting of the 34 tank wall panels. This is in addition to the two buttress panels for post-tensioning, which will be undertaken in the same way as all of Corestruc’s other reservoirs. All of the wall panels will be propped during their installation, considering the wind speeds at this height. Conventionally, only the first wall panel is propped to free up space.

Meanwhile, the roof structure consists of four columns and beams, as well as 150 hollow-core slabs. The centre portion or “core” will be constructed first, and the outer section completed as part of the among the final aspects of the programme.

While the structure, itself, demonstrates excellence in precast-concrete design and implementation, Van Rooyen says that RSMM Construction and Corestruc have also had an opportunity to show off their extensive expertise in cast-in place concrete methods.

“Supporting this water tower is a 1m-thick and 25m diameter foundation consisting of 500m2 of 30MPa cast-in-place reinforced concrete. It is underpinned by 200m2 of mass concrete blinding. This took 10 hours to place, starting at 5h00 and using two concrete pumps, while also isolating an entire ready-mix concrete plant just for this purpose,” he says.

Van Rooyen has all the reason to be proud, considering how well the project is progressing. He will soon be able to boast that he has again played his part in yet another project that has demonstrated the efficacy of precast concrete!