Kerkstoel 2000+ produces architectural precast concrete elements for highest demands

Kerkstoel 2000+ and Vollert in collaboration with Prilhofer Consulting have created a highlight in industrial series production of demanding architectural precast concrete elements in Belgium. A wide variety of precast concrete elements manufactured by the Kerkstoel Group can be found in modern residential and office buildings as well as in shopping malls, railroad stations and airports. In order to continue to set trends, the Belgian specialist in building materials located in Grobbendonk invested in a new solid, double and sandwich wall manufacturing line for versatile building component geometries and customized designs. This enables them to manufacture concrete elements of varying degrees of complexity within the same period, but without decreasing the plant productivity.

The Belgian Kerkstoel Group is one of Europe‘s leading manufacturers of ready-mixed concrete and precast concrete elements. Since the 1980s, the long-established company has accomplished real pioneering work together with its subsidiary Kerkstoel 2000+ in the field of modern, automated manufacturing of semi-precast components. In 1989, one of the world‘s first industrial series production plants was already built in the Flemish municipality of Grobbendonk near Antwerp with plant technology of Vollert. The year of 1997 was characterized by the entry into the double wall production above all for modern residential and industrial construction.

Today, Kerkstoel led by their management board chairman, Pascal Kerkstoel, is regarded as pioneer and innovation driver in excellent architecture with precast concrete elements. „This ranges from the Ericsson headquarters in Zaventem, the Eurostation II central station in Brussels through to the courthouse in Antwerp. A real architectural highlight,“ Pascal Kerkstoel proudly reports. He can be justly proud because what had been built up in Grobbendonk over the last 30 years is quite exemplary. Numerous architectural highlights and real estate projects in the Benelux countries were realized with precast concrete elements manufactured in Groobendonk.

The most modern precast factory of the 21st century erected in 2019

Pascal Kerkstoel is really convinced that „if you‘re not moving forward, you‘re falling behind“. Nowaydays, walls, floor slabs or façade elements are not only more diverse in terms of architecture, shape and size or surface quality, but also require a larger scope of work, more embedded parts or integrated special functions. At the same time, construction projects require larger capacities and the cost pressure is rising so as to remain competitive in the competition for customers and contracts. These developments present a major challenge to many manufacturers of precast concrete elements. „As our customers increasingly prefer double and solid wall elements with complicated component geometries and oversized wall areas of up to 3.80 m, we had decided to invest in another modern precast concrete production line in 2018. Certainly, the greatest investment in our history so far.“

The plant concept and the layout were developed by Prilhofer Consulting as an independent consulting firm. After all plant and performance requirements had been determined, a specification document was produced for each part of the machine technology. Based on this, Kerkstoel 2000+ and Prilhofer issued a call for tenders for the plant technology, in which the German concrete plant specialist Vollert together with RIB SAA Software Engineering and their local partner UBO Engineering successfully positioned themselves against the competitors. Prilhofer Consulting was also responsible for the implementation planning and project development, in close coordination with the project team of Vollert.

„The plant concept developed by Prilhofer Consulting certainly is very extraordinary and probably unique in Europe,“ states Philippe Marrié, as the executive sales director for the Benelux countries at Vollert. „Right from the initial planning phase, we have dealt with the requirements of Kerkstoel and Prilhofer Consulting very intensively. For manufacturing series products such as large-scale wall elements for industrial construction projects as well as architectural concrete components or wall panels with specific dimensions or surfaces on the same production line, industrial prefabrication requires an intelligent plant concept for flexible processes and a high degree of automation with the latest robot technology,“ Philippe Marrié states. The production of complicated special concrete elements, moreover, requires an even larger scope of work. This, however, would mean a longer residence time, for example, in the reinforcement station or during manual processes for walls and floor slabs with integrated wiring or with special surface coating. New technical production processes were required to solve this challenges, to ensure maximum flexibility and to reach an extremely high level of plant productivity. „Another challenge was to design the plant concept extremely compact because the location of the Kerkstoel factory situated on the banks of the Albert Canal means that building plot is very expensive. In particular, the storage area is minimized, with daily turnaround of the manufactured wall panels and floor slabs,“ explains Jürgen Schäfer, project manager at Vollert. „The objective was to achieve an annual production of up to 500,000 m² of concrete wall and floor area on a defined floor space of 4,880 m².“

Island method, „false bottom“ and maximum degree of automation

To ensure maximum flexibility while avoiding long downtimes and idle times for individual manual tasks needed for the elaborate wall and floor geometries, the island methodology was chosen. Before the casting process or after the robot-based installation of reinforcement, individual circulation pallets are transferred from the manufacturing line to separate buffer areas insolated by vertically moving, special barrier fences. „Depending on the construction project and the degree of utilization, necessary manual tasks are prepared here, such as the insertion of special reinforcement elements, embedded parts as sockets and window frames or pipework. We increase the flexibility by a factor of three with this work islands in a net-like arrangement,“ Pascal Kerkstoel states. Subsequent wall elements or floor slabs being less complex can be transported downstream on the manufacturing line, without slowing the overall process down and reducing the plant productivity. Some of the circulation pallets are moving tunnel-like beneath the elevated intermediate level.

„It is certainly a highlight of the plant concept that we work on several levels at Kerkstoel,“ explains Jürgen Schäfer. „Right from the beginning, building plot was limited owing to the geographical conditions in direct proximity to water on the Albert Canal. „Therefore, we provided different working levels and platforms,“ Schäfer adds. The overall fully-automated reinforcement preparation takes place on an elevated intermediate level. „Here, we are roughly 15 m above the ground.“ The AWM reinforcement system prepares the most different reinforcement mesh and lattice girders in a CAD/CAM-controlled process for the next walls and floors. A reinforcement robot positions them for the subsequent casting process directly on the beneath passing circulation pallet using a special lifting and lowering function. The future surface finishing station for wall and floor surfaces is situated on the same intermediate level. For this purpose, the VArio Store storage and retrieval unit removes the pre-hardened upper shell or the solid concrete element from the curing chamber, carrying it to the opposite intermediate level directly. Another planned expansion stage includes a finishing line equipped with several electric VArio Smooth surface smoothing machines here.

An intelligent MES production system of the automation specialist RIB SAA Software Engineering ensures perfect and on time supplying of construction sites and customers with the precast concrete elements needed. The system consistently controls and monitors all processes and machines in the precast concrete plant, from the work process planning, the work stations to the storage and loading processes. It is the central interface of the structural data created in the BIM model as well as to the existing ERP system. Throughput times and automated pallet allocations are permanently optimized, all machines are controlled, data is automatically tracked and processed, retrieval sequences and curing times are managed and a large number of statistics is provided. In a Smart Factory, like the Kerkstoel 2000+ plant, all this is running completely paperless. Component drawings, assignment plans, batches or the current stocks are always visualized and are available for recall by means of state-of-the-art hardware such as tablet computers or large multi-touch flat-panel displays.

Robot and laser technology for highest precision

Precise high-performance robots, turning and transport equipment as well as fully-automated timing of all processes and transport routes above all provide for an ever higher degree of automation in precast concrete plants today. This is not only important with regard to the plant productivity but also ensures a consistently high quality standard and low level of concrete and material waste and thus a higher resource efficiency.

Robotics in combination with state-of-the-art laser technology, permanent quality inspections and zero-defect strategy are the keywords here. The Smart Set² shuttering robot is a multifunction robot of the latest generation, combining innovative technology with high performance levels regarding movement speed and acceleration. Depending on the wall and floor slab type, the Smart Set robot line at Kerkstoel is positioning the up to 500 mm high shuttering systems under CAD/CAM control and provides for pre-plotting of the contours of embedded parts and reinforcement components, if required. For the demolding process, modern optical scanning systems scan the surface and register the type and position of the shuttering profiles before the Smart Set removes them and, after cleaning, puts them into the storage magazine or transfers them to the feeding section for the next shuttering process. Five iTwo Smart laser projection systems are installed along the transport line for permanent quality control and monitoring of the tolerances to be complied with, for example, in case of manual reinforcement supplementation.

Optimum concrete cycle times and exact concrete distribution

Another essential quality factor regarding the later wall quality is the casting process. A fully automated, gantry-guided Smart Cast concrete distributor provides for optimum concrete cycle times and exact concrete distribution according to the zero-defects strategy. Using too much or insufficient concrete of the specified discharge quantity when casting is minimized in this way and reliable even at a very high level of availability. Compaction of the concrete by means of a combined VArio Compact² shaking/vibrating unit ensures an optimum upper shell of the solid concrete element in fair-faced concrete quality as well as a perfect compaction of the more strongly reinforced load-bearing shell of double and sandwich walls. Another vibrating station is installed in the area of the turning device. The low-frequency vibration movement is generated by four unbalance drives, and the concrete is compacted as a result. The compaction energy is automatically adjusted, depending on the dead weight of the concrete element. This allows for an optimum, circular vibration movement with low noise emission. An energy efficient curing process is ensured by an insulated VArio Cure curing chamber with four rack towers and a total of 56 compartments. A special heat circulation system provides for an even temperature distribution.

Essential technical innovations for increased cycle times and on the topics of ergonomics and occupational safety were implemented in the double and sandwich wall production line at Kerkstoel 2000+. Traditionally, the tensioning arms for pre-locking of the upper shell prior to the turning process are inserted as well as removed manually. This is not only time-consuming but also a strong physical burden given the high dead weight of the tensioning arms. At the Vario Turn turning device installed at Kerkstoel, tensioning arms directly attached to the turning device make sure that the upper shell of the double or sandwich wall is reliably held during the lifting and turning movement of the turning beam. As an option, an automated wall thickness adjustment system can adjust and set the height of the double wall automatically. The height fixation of the tensioning arms can also be designed variably and thus, there is nothing to prevent the production of core-insulated double walls. Pre-locking of the upper shell to the second shell is precisely guaranteed in all directions.

Kerkstoel Group sets another milestone

„Kerkstoel 2000+ has set another milestone with the new precast concrete plant in Grobbendonk,“ states Philipp Marrié confidently. The plant has already been producing high-quality double walls for several prestigious construction projects in the greater Antwerp area but also the other Benelux countries since the end of 2019. Now, it is possible to manufacture special customized designs or special concrete elements as well as large series for major construction projects simultaneously. „Technology, a great deal of expertise, maximum quality and absolute adherence to schedules, this is what our customers can still rely on,“ Pascal Kerkstoel says in view of the additional growth of his family-run company with great tradition and pioneer in precast concrete production.