The enclosure dam between the Wadden Sea and the Ijsselmeer has protected large parts of the Netherlands against flooding since 1932. Meanwhile, the building structure is in need of refurbishment and modernization owing to permanent environmental impacts. In a multi-annual project, the stability of the dam is to be improved by innovative concrete blocks: „Levvel-blocs“ especially developed for this purpose by the Dutch project company Levvel are used on the lower embankment and special basalt quattro blocks made by Holcim Coastal B.V. are used for the upper bank.
Innovative concrete elements for highest demands
The Dutch company Holcim Coastal B.V. is a specialist in hydraulic construction and coastal protection. Jean-Pierre Quartaert, general manager at Holcim Coastal B.V., explains the procedure for selecting appropriate concrete elements for this project and similar ones: „We were aiming at high stability in conjunction with durability and a minimum input of material.”
„Now, we needed the adequate technology for the production of the concrete elements,“ explains project manager Jörg Switala. „In view of the large quantity and the most demanding end use, highest operational safety and perfect mixture homogeneity were key factors for us here.“ Thus, we chose BHS-Sonthofen, the expert in mixing technology, being most familiar with demanding major projects. The Dutch Holcim plant located in Alphen aan den Rijn, where the elements are manufactured and shipped, required two mixers with a daily capacity of 520 m³ at the start of the project in 2019. The company will supply concrete for 700,000 m² of dam area in total until the project completion in 2023.
BHS technology for the required homogeneity
For this field of application, André Däschlein, sales manager mixing and crushing technology at BHS, recommended the twin-shaft batch mixer of type DKX, having already proven its worth in the concrete industry. „Due to several decades of extensive know-how in the field of concrete, we are able to draw on experiences from a large number of similar projects,“ Däschlein says. „Therefore, we were quite sure that the twin-shaft batch mixer provides the required high mixture homogeneity“
The secret behind an intensive exchange of materials that can be achieved within a short time is the three-dimensional mixing principle: Two shafts generate circular movement patterns with a turbulent overlap zone, making optimum use of the energy input for a uniform distribution of the mixture. Thus, the high mixture homogeneity goes hand in hand with an as low as possible energy demand – a crucial argument for a project of this dimension. Other important factors are the high level of operational safety and machine uptime, which are absolutely necessary for the anticipated high degree of capacity utilization.
BHS mixers perfectly suited for concrete blocks
The advisory competence of BHS-Sonthofen regarding concrete elements is based on many years of professional experience in the industry. „Customers are still surprised that BHS mixers are also suited for concrete products and paving blocks with extreme requirements on the mixture homogeneity,“ Däschlein states. „Within the DKX series, we offer a special mixer configuration for concrete blocks, operating already at numerous companies with great success.“ The adapted speed, accurate humidity measurement and water dosing make the twin-shaft batch mixer of BHS the perfect choice even for most demanding products.
Before the start of the dam refurbishment project, BHS mixers have already been used for concrete blocks in the Netherlands: Excluton, the operating company of Europe‘s largest concrete block factory based in the Netherlands, is using twin-shaft batch mixers of BHS for the production of concrete for the top layer as well as core concrete. In cooperation with the Dutch company Loke BV, BHS has already supplied concrete mixing plants equipped with DKX mixers in 2014; until today, they are producing top-class concrete 22 hours a day and six days a week without any outage. Such successful projects confirm Holcim project manager, Switala, in his choice: „With BHS-Sonthofen, we found a strong partner regarding mixing technology – it is extremely important to use well-proven technology of high quality for a project of this dimension.“