A resurgence of interest in infrastructure has been welcomed by South African entrepreneurs, but the urgency of many projects places significant demands on inputs like off-the-shelf.
“This is where admixtures play a critical role in ensuring ready-mixed concrete meets the highest standards while meeting accelerated timelines,” says Michelle Fick, Business Unit Development for Aesthetics concrete and major accounts at CHRYSO South Africa.
Fick emphasizes the importance of durable concrete in giving structures their expected lifespan, providing value for money to end customers. Large ready pours are at the heart of many of these projects and improve the pace of construction.
“For example, in a recent reservoir project with several large pours, CHRYSO was able to contribute a concrete mix design that ensured low shrinkage while achieving durable, watertight concrete,” she says. “Our products helped to keep the heat of hydration as low as possible and to prevent cracking due to plastic shrinkage.”
This was resolved by using CHRYSO® Serenis – a shrinkage inhibitor – in the wall flange, floor slab and roof slab. To help heal any leaky cracks and construction joints, CHRYSO® CWA 10 cement-based waterproofing admixture for crystalline concrete has been added to the mix. Dolomite aggregates that were used to produce a lower coefficient of thermal expansion also had a low water demand; CHRYSO® Omega 178, a high performance water-reducing superplasticizer, was therefore used to reduce the water content.
Road construction and improvement relies on a variety of precast concrete components such as culverts and pipes, where the curing time directly affects the rate of production. Here, she says, CHRYSO offers its range of accelerators to speed up the curing process and reduce the turnaround time for each precast element. There are also superplasticizers to improve the durability and workability of concrete with reduced water and cement content.
Fick explains that these solutions are also important in high-rise buildings where concrete is pumped to great heights, enabling rapid progress. For a recently completed skyscraper in Sandton, the ready-mix included CHRYSO Omega 140AFR, a hybrid plasticizer/super-plasticizer, along with the super-plasticizer CHRYSO® Optima 100. The result was a mix with slump of 180 mm which could be pumped 200 meters high.
Curing compounds are another important product line for building faster, with various bases such as wax, resin, acrylic and water for different applications. This ensures efficient curing with minimal effort and labor.
“Key to the application of our admixture solutions is our research and development laboratory in Johannesburg,” says Fick. “Our resources here include a valuable database of past projects, aggregates and cement types from around the country, allowing us to quickly develop and apply solutions for contractors and ready-mixed concrete suppliers. ‘use.”
She notes that this database can provide guidance for a project’s concrete mix, based on experience from previous projects in the same area using the same sources of aggregate and sand. This allows CHRYSO to speed up the identification of the most suitable additive for this specific application.