Increasing wind farm construction across South Africa has led to a high demand for admixtures that help ensure durable concrete foundations for wind turbines constructed in remote locations and under harsh environmental conditions such as extreme temperatures.

Chryso Southern Africa general manager: technical and product support Patrick Flannigan highlights the critical role of concrete admixtures in ensuring durability and structural integrity, noting: "Wind turbine bases are subjected to some of the harshest environmental conditions, making durability a top priority for concrete mixes used in these foundations."

The bases or foundations of wind turbines are large structures, often reaching diameters of approximately 20 m and sometimes matching this in height. As a result of their mass, the concrete placements usually 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. 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.”

In addition, the remote locations of wind farms make concrete delivery a logistical challenge, as readymix concrete plants are typically far from the construction site and, if 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 Southern Africa offers a range of admixtures aimed at addressing these challenges. The CHRYSO Enviromix range is used to optimise early and late-age strength development, especially in mixes containing SCMs. The plasticiser is designed to improve cohesion and lower viscosity, enhancing mix homogeneity and durability. For particularly challenging aggregates, the CHRYSO Quad solution provides targeted performance enhancement, aimed at ensuring consistent workability and strength development even in demanding mix designs.

Flannigan notes that Chryso's superplasticiser formulation is a key advantage. The CHRYSO Optima range, designed specifically for readymix concrete, is not water-sensitive, aids in producing durable low viscosity concrete mixes and is particularly robust. Engineered with patented phosphonate technology, it ensures prolonged plasticity which is ideal for projects with long distance concrete transportation. It also helps provide effective water reduction, maintaining workability for 30 minutes 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.

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.

In addition, CHRYSO Curing Compounds help reduce shrinkage cracks and improve concrete’s overall strength and impermeability. These compounds help extend the durability of wind turbine bases by reducing moisture loss during curing.