CoreSlab, a leading South African precast-concrete specialist, manufactured and installed a total of 260 hollow-core slabs (HCS) in only four days to assist Rokkon Development accelerate the construction of a new residential development in the Polokwane central-business district (CBD).

It would have taken more than 20 days for the developer’s construction arm to build the concrete floor slabs for the new apartment blocks using in-situ techniques as initially intended. This includes the extensive process of installing, assembling and removing props and formwork, steel fixing, as well as pouring the concrete, waiting for it to cure and stripping the shuttering.

Alternatively, the HCS were manufactured and cut to size according to the building dimensions immediately after the concrete had reached the required strength at CoreSlab’s cutting-edge factory, located just outside the Polokwane CBD.

The “planks”, which are significantly lighter than a large solid concrete floor slab of equal thickness or strength due to the use of fewer raw materials in their manufacture, were also cost-effectively transported to site where they were placed directly on a 30mm to 45mm-thick levelling screed on the masonry walls.

Levelled and grouted to complete the floor structures, the principal contracting teams and trades are then able to work above and below almost immediately to significantly accelerate a building project.

Johan Muller administered the efficient installation of the slabs on behalf of CoreSlab.

“This is an extremely fast-track project, and it has certainly been very rewarding to see just how swiftly it has progressed. The rapid rate at which the various apartment blocks have climbed out of the ground bears testament to the skills and capabilities of both the main contractor and CoreSlab, which ensured the accurate construction of the floor slabs to avoid wastage and delays,” Muller says.

In January 2020, work had commenced on the foundations of the development and, a month later, all the floor slabs for the 14 apartment blocks had been completed to enable the brick laying teams to start working at the next level, ahead of the completion of the roof structures.

Double units comprise 80 m² of pre-cast concrete slabs to accommodate a total of 26 units – 13 at ground level and 13 on the first level.

CoreSlab can install an element every six minutes to complete a suspended floor slab in record time.

Working according to a predetermined schedule by the main contractor, the company deployed a 24t mobile crane to lift and place the HCS directly from the truck trailers as they arrived. It was equipped with special lifting tackle that was designed by CoreSlab’s engineers to facilitate the rapid and efficient placement of the slabs.

Certainly, another advantage of HCS on this project is that it freed up space in a heavily built-up environment by eliminating the need to co-ordinate the timely delivery of ready-mix concrete and deploy a concrete pump on site.

Meanwhile, this approach also complemented Rokkon Development’s ongoing focus on health and safety. The floor slabs are manufactured at ground level at CoreSlab’s factory and installed by a small skilled and experienced team, comprising seven people, including a foreman.

Jaco de Bruin, Managing Director of CoreSlab, says that he is proud of the company’s continued association with Rokkon Development.

“We have worked with the company on previous residential projects. Renowned for its meticulous workmanship, reliability and timely delivery, Rokkon Development has earned an enviable reputation in the building industry. Certainly, this is evidenced by the high quality of the company’s office complexes, hospitals, game ranches, retail centres, show rooms and residential developments,” De Bruin concludes.