The Afsluitsdijk dam, located between the Wadden Sea and the Ijsselmeer, has protected large parts of the Netherlands from flooding since 1932. Due to constant environmental influences, the structure is now in need of renovation and modernization. The dam should become more stable with the help of innovative concrete blocks introduced over the course of a multi-year project. This will be achieved through the use of “Levvel-blocs” specially developed by Dutch project company Levvel for the lower embankment and special basalt Quattroblocks from Holcim Coastal B.V. for the upper embankment.
Dutch company Holcim Coastal B.V. specializes in hydraulic engineering and coastal protection. Jean-Pierre Quartaert, Managing Director of Holcim Coastal B.V., explains the procedure for selecting suitable concrete elements for this project and similar ones: “Our goal was to combine a high degree of stability with durability and using the smallest amount of materials possible. That’s why our Quattroblock – introduced in April 2018 – consists of four interconnected columns. It is important to test these kinds of new designs extensively in advance.” The results were impressive: compared to their predecessors (the pure concrete blocks), the Quattroblocks are 40 percent more stable.
“We now require the appropriate technology to produce the concrete elements,” explains project manager Jörg Switala. “In view of the large quantity and demanding end application, the highest degree of operational reliability and perfect level of homogeneity were particularly important to us.” The decision fell to BHS-Sonthofen who are very familiar with large-scale, demanding projects. The Dutch Holcim factory in Alphen aan den Rijn – where the elements are manufactured and shipped – required two mixers in order to produce a daily throughput of 520 m³ for the start of the project in 2019. The company is to supply concrete for a total of 700,000 square meters of dam area until the end of the project in 2023.
André Däschlein, Sales Director Mixing and Crushing Technology at BHS, recommended the use of the industry standard twin-shaft batch mixer of type DKX that would provide the necessary high level of homogeneity for the task at hand.
The secret behind the intensive material exchange that can be achieved in a very short amount of time is the three-dimensional mixing principle: two shafts generate circular movements with a turbulent overlapping area, so that the energy introduced is optimally used for an even distribution of the mix. Therefore, the high level of mixture homogeneity is the perfect solution to needing to use the lowest amount of energy possible – a decisive factor for a project of this size. This also results in a high level of operational reliability and machine availability, which are absolutely necessary given the expected high capacity utilization.
BHS-Sonthofen’s ability to provide consultation regarding concrete elements is based on many years of experience in the industry. “Customers continue to be surprised that the BHS mixer is also suitable for concrete products and blocks that come with the highest demands on mixture homogeneity,” says Däschlein. “Our DKX series includes a special mixer configuration for concrete blocks, which is already being used by numerous companies with great success.” The adjusted speed, exact moisture measurement and water dosage makes the twin-shaft batch mixer the perfect choice also for very demanding products.