Caption: The structure comprises three sections or ‘rotations’ consisting of columns that are connected to that portion of the spiral beam.
This is Part 1 of a three-part article.
The City of Ekurhuleni’s Water & Sanitation Department is at the cutting-edge of precast-concrete technology. This water-services provider has already successfully completed the construction of four prefabricated reservoirs. With another precast concrete water-retaining structure nearing completion, it was just a matter of time before the Water & Sanitation Department would take its concept even further.
A new water tower is being constructed alongside one of these precast-concrete reservoirs. It too, when completed later this year, will have been almost entirely prefabricated in a state-of-the-art factory and skilfully integrated on site. The only in-situ components include the tank floor slab and the foundation.
When finalised later this year, this will be the first precast-concrete water tower in Africa. It will have a final height of 36m and a capacity of 2,5ML.
The municipality opted for a precast-concrete water tower because it was faster and more cost-effective to build. This while also providing a final structure of an exceptionally high quality which, in turn, will provide operating cost savings through reduced maintenance requirements.
The efficacy of prefabrication had proven itself time and again on each of the projects the Water & Sanitation Department completed. Meanwhile, its professional team had also become more proficient in executing the works, refining and honing the sophisticated method from one project to the next.
The water services provider is again being supported by Tangos Consulting Engineers, the design engineer and project manager, and Infinite Consulting Engineers, a structural engineer with an extensive pedigree in the design and supervision of precast-concrete structures. This is in addition to RSMM Construction, the principal contractor, and Corestruc, a precast-concrete turnkey contractor. Partnering Corestruc with its extensive precast-concrete know-how, which includes manufacture, transport and rigging, RSMM Construction has earned a reputation for the exceptionally high quality of its water-retaining structures. This while building them in fraction of the time that it would have taken using conventional cast-in-place methods.
The construction of the precast-concrete water tower will be completed in only 14 months compared to between the two and three years that it would take using traditional methods. Considering that this is the first precast-concrete water tower to be built by the team, it is taking slightly longer to construct. The other water-retaining structures will be completed in only nine months, bearing in mind that the tower constructed above the footing took only six months to build.
It will also have a design life of 100 years if maintained appropriately, considering the high-performance concrete used to manufacture each individual component.
Corestruc’s quality control technicians precisely calculate the moisture content of aggregates and factor in water from admixtures to make the necessary modifications to maintain the optimum water-to-cement ratio. The company is also judicious in its selection of aggregates to ensure that they are as impermeable as possible. Furthermore, admixtures are used to modify fresh or hardened concrete. All of these produce an almost impermeable concrete element that can withstand damaging chloride and sulphate ions, as well as aggressive chemicals.
