With the ongoing construction of wind farms across South Africa, Chryso Southern Africa has seen an increasing demand for its construction admixtures. Contractors are leveraging these solutions to mitigate challenges posed by remote site locations and extreme temperature variations.

Patrick Flannigan, General Manager Technical and Product Support at Chryso Southern Africa, highlights the critical role of concrete admixtures in ensuring durability and structural integrity. "Wind turbine bases are subjected to some of the harshest environmental conditions, making durability a top priority for concrete mixes used in these foundations," he explains.

Addressing Thermal Contraction Cracking

The bases or foundations of wind turbines are substantial, often reaching diameters of approximately 20 metres and sometimes matching this in height. Given their mass, these concrete placements typically contain high Portland cement content, leading to significant heat buildup during the hydration process. The subsequent dissipation of heat can cause thermal contraction cracking, potentially compromising the structural soundness of the base.

“To mitigate this,” Flannigan explains, “contractors often incorporate Supplementary Cementitious Materials (SCMs) such as fly ash or slag alongside Portland cement. This approach is both cost effective and environmentally friendly but can impact the early and late-age strength development of the concrete.”

Managing Workability and Placement Challenges

“Another challenge arises from the dense steel reinforcement within wind turbine foundations. This congestion necessitates high slump concrete which, if not managed correctly, can lead to segregation, negatively affecting durability,” he continues.

Additionally, the remote locations of wind farms make concrete delivery a logistical challenge. Readymix concrete plants are typically far from the construction site, and where site batching is done, the batching plant is often at a significant distance from the foundations. This requires solutions that can maintain concrete workability over extended periods.

Chryso’s Innovative Solutions

Chryso Southern Africa offers a robust range of admixtures to address these challenges effectively. The CHRYSO® Enviromix® range is widely used to optimise early and late-age strength development, especially in mixes containing SCMs This plasticiser improves cohesion and lowers viscosity, enhancing mix homogeneity and durability. For particularly challenging aggregates, the CHRYSO® Quad solution provides targeted performance enhancement, ensuring consistent workability and strength development even in demanding mix designs. Together, these innovations support superior concrete quality across diverse applications.

Flannigan notes that Chryso's expertise in superplasticiser formulation is a key advantage. "Matching superplasticisers with cement and aggregate chemistry is one of Chryso’s strengths.

The CHRYSO® Optima range, designed specifically for readymix concrete, offers exceptional robustness. This product is not water-sensitive and aids in producing durable low viscosity concrete mixes. Engineered with patented phosphonate technology, it ensures prolonged plasticity which is invaluable for projects with long distance concrete transportation. It also provides effective water reduction, maintaining workability for 30 to 45 minutes while still achieving high strength.

For precast concrete applications, the CHRYSO® Premia range is ideal and delivers rapid strength development and superior surface finish, making it a preferred solution for precast project plants aiming for high productivity and consistent quality.

Additional Performance Enhancers

To support long distance readymix concrete transportation, CHRYSO® Optima ensures extended workability and pumpability for planned deliveries. For unexpected delays or returned readymix concrete, CHRYSO® Rescue Pack enables controlled curing rates, prevents cold joint formation and ensures proper compaction, especially critical in large pours like wind turbine foundations.

Additionally, CHRYSO® Curing Compounds help reduce shrinkage cracks and improve the concrete’s overall strength and impermeability. These compounds play a vital role in extending the durability of wind turbine bases by reducing moisture loss during curing.

“With our innovative range of admixtures, Chryso Southern Africa continues to support the construction of resilient and long lasting wind farm infrastructure, helping contractors overcome the unique challenges posed by these remote and demanding projects,” Flannigan concludes.