CoreSlab, a leading designer and manufacturer of precast concrete systems, has worked with many contractors on a myriad of successful projects, ranging from civil-engineering infrastructure to private- and public-sector building developments.
Important insights have been garnered over the years working alongside these companies, including both emerging and large established contractors.
CoreSlab has incorporated these experiences into its own processes to ensure it remains the first point of call for contractors’ precast concrete requirements for hybrid-concrete construction (HCC) projects. Importantly, this approach has also played a major role in driving greater uptake of HCC technologies by the South African contracting fraternity.
By working alongside a leader in the field, contractors have been able to fully exploit the many benefits of HCC, including providing a more convenient manner of building. Precast concrete technologies are also ideally suited to applications that require a high-quality aesthetic finish, while contributing towards a safer site and lowering the overall cost of the build.
Jaco de Bruin, managing director of CoreSlab, says that, firstly, contractors place immense credence on the casting operation of their supplier, with guaranteed high quality and precision in the design and manufacturing phases an absolute imperative.
“They also want to be ensured of efficiencies at the operation,” De Bruin says.
“Productivity is dependent upon a number of factors, including product flow design. This relies heavily on the product mix, stock and the level of mechanisation at the operation, in addition to the type of forms and concrete manufacturing processes. Other important factors that have a direct bearing on our proficiencies on a project include demoulding, curing and storage methods. Moreover, CoreSlab takes into consideration the function and capacity of the concrete moulds, assessing life-in-use; placing and compaction of concrete, including the vibrating method that will be adopted; curing process; cost; demoulding; and cycle times.”
Significant time and effort is also invested into planning the lifting during demoulding. This includes the lifting points, as well as rotation and orientation of the precast concrete elements. Other factors include the curing position and storage of the precast concrete elements, as well as their movement inside the operation.
CoreSlab’s state-of-the-art factory is based in Limpopo, and has been the source of supply of quality precast concrete items for, among others, reservoirs, sports complexes and bridges. This is in addition to retail, commercial and hospitality-related building projects.
On most of these projects, CoreSlab has worked alongside Corestruc, which assists with the installation of the precast concrete items and managing this component of the works.
CoreFleet helps with the logistical planning and transportation of the heavy precast concrete elements to site – another important consideration in HCC projects.
In many instances, transport and logistical activities have to be undertaken on a just-in-time basis, while planned to avoid double-handling and storage requirements. Projects have also benefitted from specialist equipment that has been designed specifically for the optimal transport and offloading of heavy precast concrete elements.
Meanwhile, Corehire, a crane specialist, is tasked with lifting and placing them during the installation phases.
De Bruin says availability of cranes, as well as high levels of safety during the lifting and placement of the heavy precast concrete items is also important requirements for contractors.
“One of the many advantages of precast concrete technologies is that it provides a safer alternative to conventional in-situ construction techniques, with smaller and experienced teams working at heights over shorter periods. By exercising direct control over the crane requirements and materials handling components of the operation, we have been able to mitigate any external risks that may compromise safety on the site,” he says.
CoreSlab and Corestruc also work closely with the main contractor in the early phases to determine the erection sequence, as well as the interface between the specialist precast installation teams and those of the main contractors.
As De Bruin notes, a successful HCC project is extremely reliant on team work. In most instances, the precast concrete aspect of the works is on the critical path of the project and the installation of the modular system will, therefore, have a direct negative impact on the programme if not properly managed.
A similar approach is also taken in the design phases, with CoreSlab working closely with the consulting and structural engineering teams in optimising the precast concrete component of the build. Many designers are unfamiliar with the technology and still require important input from experts in the field.
He says while there has been a marked increase in interest in HCC technologies, it will take time for this method of construction to reach its full potential in South Africa.
“It has taken time for reputable participants in the industry, including CORE group companies, to change the negative perception towards precast concrete technologies due mainly to poor workmanship in the past. Stringent quality-control processes are, therefore, an imperative in the industry, especially at a time when HCC technology is still growing,” De Bruin says.
While the quality of processes and efficiencies at the plant, as well as transport and handling of the precast concrete elements are all important requirements for any successful HCC project, stitching remains the single-biggest consideration.
This is an extremely complex aspect of any HCC project and is dependent upon specialist skills. De Bruin attributes many past failures in HCC specifically to lack of experience in the field.
The design of the stitching is already tackled in the early phases of the project.
Important aspects include the configuration of the rebar and the design of the moulds, which also have a direct bearing on the configuration of the steel reinforcement.
In addition, serious thought is given to convenient access to the elements, also often designed to assist in the forming of the shutter.
At the same time, meticulous attention is paid to the concrete mix design, as well as its compaction and curing in stitching applications. CoreSlab uses its own continuously graded and low-shrinkage concrete for stitching.
De Bruin concludes that the company’s involvement with a number of contractors bears testament to the growth of HCC in the country, and the meaningful role that this technology has to play in the future.