The global precast-concrete industry can lay claim to being a leading driver of innovation in the construction industry.
This has been an ongoing process since the lattice girder was harnessed in the 1960s to allow for the first large-scale industrial production of precast-concrete elements.
Comprising mostly fixed beds in open areas and make-shift factories, these simple production processes were a solid platform upon which further advances in concrete design and application would eventually be made to significantly accelerate construction projects and achieve greater levels of precision on sites.
The industry would take immense strides forward between 1985 and 2000 by harnessing information technologies, such as computer-aided design and programmable-logic controllers, to break new boundaries in efficiencies and precision in the manufacturing processes.
These developments were supported by significantly improved mix designs to produce a durable concrete that would cure faster and provide high-early compressive strengths.
Forms and moulds could now be stripped within a day to allow the industry to compete effectively against cast-in-place, or in-situ construction methods.
What has now become standard practice in the industry is a far cry from those fledgling years when 20 MPa was the acceptable 28-day compressive strength period under ideal curing periods.
Importantly, ongoing research and development in the field of concrete mixes would also allow the industry to produce an increasingly durable precast-concrete element in response to the demands of property developers and state drivers of infrastructure.
Jaco de Bruin, managing director of CoreSlab, says that the high durability of the company’s systems has become a significant selling point, especially in this challenging economic environment in which budgets for critical infrastructure have been cut, despite a growing back-log in essential services.
“Precast-concrete is a long-lasting construction material that requires minimal maintenance and, therefore, plays a large part in reducing the lifecycle cost of the asset. This construction material will stand the test of time to provide long-term value for the owner of the asset, and
many state bodies, especially the municipalities, now view this trait as a major benefit when planning infrastructure projects,” De Bruin says.
The company’s systems have been used to build, among other infrastructure, long-lasting reservoirs, water-treatment works, booster pump stations and service tunnels, while a precast-concrete solution has also been developed especially for the large-scale roll-out of sports and recreational facilities in outlying areas of the country.
Its structural systems, comprising precast-concrete elements that exceed 50 MPa, have also been used to construct high quality commercial, leisure and retail property developments.
Certainly, the high durability of precast concrete systems can be directly attributed to the industry’s focus on designing a concrete with a low permeability.
Water penetrates concrete with a high permeability and corrodes the reinforcing bar and this eventually leads to the deterioration of the long-term performance of structures, some of which have been designed to have a life of between 50 to 100 years.
While a low permeability material is designed by raising the compressive strength of the concrete and lowering the water-to-cement (w/c) ratio, many enterprising industry participants continue to find other novel ways of testing traditional limitations in concrete mix designs to enhance the overall performance of their systems.
For example, CoreSlab has also introduced silica fume, an industrial by-product, into its concrete mix to supplement some of the cement content to produce a denser concrete micro structure.
Ongoing developments in construction chemicals and additives have also greatly assisted the industry in innovating as is demonstrated by concretes with lower w/c ratios and higher compressive strengths than those mixes commonly used on traditional cast-in-place projects.
Importantly, these high slump mixes without extra water have also ensured improved “flow-ability” of the concrete in the various moulds and forms to manufacture consistently high quality precast-concrete elements.
However, De Bruin notes that a significant competitive edge for precast-concrete producers is the absolute control that they have over the entire cycle by being far removed from the many variances that are encountered on a typical construction site.
In these factory settings, for example, accurate quantities of chemicals and admixtures can be easily added to a mixer to produce identical batches of concrete to ensure consistency on projects.
CoreSlab’s focus on constantly maintaining high quality manufacturing standards starts with the various basic raw materials, namely the washed sand and aggregates that are fed into its state-of-the-art factory in Polokwane, Limpopo.
Sensors inside the operation also continuously monitor the temperature and moisture content of the mix, before the concrete is poured into specialised forms and moulds to ensure high levels of precision.
A separate steel-fixing yard also ensures a high quality reinforcing in the concrete casing to further bolster quality levels at its factory.
However, he concurs that the South African precast concrete industry still has a long journey to travel when one considers the high level of sophistication of its international counterparts, which are already transitioning into the so-called “Fourth Industrial Revolution”.
This digital era is defined by autonomous production methods, as well as interconnected machines and plants to significantly improve the efficiency levels of factories.
Meanwhile, technologies, such as Building Information Modelling, improve the transparent and real-time sharing of designs between the many representatives of professional teams working on large projects.
Nevertheless, De Bruin says that South African industry participants will have to tread carefully as they advance, considering the unique socio-economic environment in which they operate.
“It is a sensitive balancing act. Construction projects should create many employment opportunities for South African citizens. However, these should be of a long-term nature and provide ample prospect for employees to develop their skills set and, therefore, earn a decent livelihood. At the moment, precast-concrete factories can take pride in being labour intensive and secure environments in which employees can grow,” he concludes.