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ADMIXTURES

The remote location of wind farms and the sheer volume of concrete required for wind turbine bases are among a range of challenges facing contractors, but CHRYSO Southern Africa has the solutions. CONCRETE SOLUTIONS FOR WIND TURBINE BASES

Left: Since wind turbines are typically constructed in remote areas, delivering readymix concrete quickly from the plant to the construction site can be dif cult. Middle: CHRYSO ® Retarders can facilitate the long-haul delivery of the readymix concrete or create a slower rate of cure. Right: CHRYSO ® Retarders and CHRYSO ® Superplasticizers from CHRYSO Southern Africa provide the solution to challenges faced with wind turbine base construction.

W ith large towers, some over 100 m in height made up of 20 m tower segments, wind turbines require strong and durable foundations of reinforced concrete to keep them grounded and secure. Each concrete foundation – or base – is in the region of 20 m in diameter and 1,8 m in height, with a portion buried below the surface. Since wind turbines are typically constructed in remote areas, delivering readymix concrete quickly from the plant to the construction site can be di cult. Even with site batching, there are often awkward and long distances from the batching plant to the foundations. In addition to this, high slump concrete is often required for wind turbine foundations due to possible issues with concrete placement and consolidation, which may occur as a result of congestion of reinforcement in the foundation. Segregation is a danger when dealing with high slump concrete, as this compromises its durability. CHRYSO ® Retarders can facilitate the long-haul delivery of the readymix concrete or create a slower rate of cure. These quality admixtures also allow for concrete to be placed without fear of cold joints forming and enable concrete to remain plastic long enough to be fully compacted. To counteract this, CHRYSO ® Superplasticizers can be used to create a cohesive low viscous and durable concrete mix. One of the most popular for this type of application is CHRYSO ® Fluid Optima 100. This admixture is not water sensitive and assists in producing

robust concrete mixes that are easy to use even under the most challenging conditions. These mass concrete placements tend to be high in Portland cement and therefore often suffer from the build-up and dissipation of heat during the hydration process. This can lead to thermal contraction cracking as soon as the concrete hardens – compromising the structural integrity and durability of the foundation. Thermal contraction cracking can be avoided by using supplementary cementitious materials (SCMs) like y ash or slag in combination with Portland cement. This option is not only environmentally friendly, but also economical. However, SCMs can impact on the early and late age strength development of concrete. Applying a curing compound from the CHRYSO ® Cure Range to the foundations will reduce the incidence of shrinkage cracks and promote better strength gain characteristics. Curing compounds also increase the concrete’s impermeability, making it more durable. a.b.e., which is a CHRYSO Group company, supplies duragrout WF for grouting and bedding of structural elements and other patch repair systems that may be required for wind turbines. In a further innovation, CHRYSO has partnered with Maturix to develop an innovative sensor solution with a digital cloud platform to monitor the maturity of the concrete. It has been used worldwide on more than 350 in-situ and precast projects. This cloud-based solution helps the construction industry to monitor concrete curing and hardening through hydration temperature measurements. 

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CONSTRUCTION WORLD NOVEMBER 2020