AFRICA’S FIRST PRECAST CONCRETE WATER TOWER BUILT PART 2

Caption: The superstructure consists of 12 tapered beams connected to the columns of the last rotation.

This is Part 2 of a three-part article.

The water tower design is the outcome of years of research and development by Corestruc and Infinite Consulting Engineers, followed by a sizeable investment into the new formwork required to manufacture the various concrete elements that make up the structure. These are already being used to fabricate the precast-concrete elements for another precast-concrete water tower that is also being built in the municipal jurisdiction. Further structures are also being planned by other municipalities as they explore more efficient and cost-effective ways of augmenting water supply, a critical challenge in the country.

They include the forms used to manufacture the 12 columns and spiral beam elements for each of the three sections or “rotations” that comprise the outer portion of the tower. These 30 interconnected semi-circular prefabricated elements wrap around the structure providing the necessary support, while also offering a striking aesthetic effect. The two columns are fixed via the protruding dowels that pass through the underside and topside of the spiral beam which is then filled with in-situ concrete. This process was repeated until the columns reached their final height.

Then there are the 15 prefabricated elements that make up the 3,6m-diameter shaft, which is constructed at the same time as the outer portion of the structure. Equipped with precast-concrete stairwells with balustrades, it leads to the underside of the prefabricated tank. Thereafter, the shaft connects with stacked precast concrete pipes equipped with a cat ladder. Cast into the reservoir floor slab, this top portion of the shaft will traverse through the water-retaining structure to a manhole on the roof.

The superstructure consists of 12 tapered beams connected to the columns of the last rotation. Resting on bearing pads, they will carry and distribute the load of the precast concrete tank and its contents.

Installed in the triangular-shaped junctions between the tapered beams, cut-to-size and shape hollow-core slabs serve as the shutter for the in-situ foundation for the water-retaining structure. Coping panels have been installed along the perimeter providing an aesthetically pleasing finish.

To ensure the very high levels of accuracy required for this precast-concrete structure, Corestruc has also invested in a robotic total station. It is also fast and highly efficient, which is precast concrete’s ultimate value proposition. This technology is making the company even more efficient at what it does so well.

Meyer van Rooyen, a seasoned Corestruc Project Manager, who has supervised all precast-concrete work thus far, says that there is very little scope for error on this project. “We have achieved tight 15mm tolerances throughout the construction of the three rotations of the substructure, starting with the placement of the first-rotation columns on the in-situ foundation. Among other factors, this is also facilitated by our precise manufacturing processes. Each element undergoes extensive quality assurance before it is dispatched and again once it has arrived on site. Once the elements have been safely transported to site and as the last component in Corestruc’s precast-concrete value chain, the responsibility rests with my team of riggers to maintain the highest levels of productivity, efficiency and accuracy,” Van Rooyen says.