Mobile concrete for rapid particles

For over 25 years, the Euromix series made by SBM Mineral Processing has defined the standards in supermobile concrete mixing technology. More than 300 units have been placed worldwide to date – with a total of 18 plants, the German-Austrian company Mobile Betonkonzepte GmbH (Mobile Concrete Concepts, MBK) maintains one of the largest Euromix fleets. And with a total of around 600,000 m³ (785,000 yd³) of concrete – including highly specific special concretes – the FAIR particle accelerator centre in Darmstadt, which is currently under construction, is one of the top references for MBK and SBM. The new particle accelerator centre FAIR (Facility for Antiproton and Ion Research), which is currently being built on an area of around 15 hectares (37 acres) at the GSI Helmholtz Centre for Heavy Ion Research in Darmstadt, is one of the most ambitious large-scale construction projects in international top-level research.

At the heart of FAIR there is a 1,100-m (1,200 yds.) ring accelerator in which electrically charged ions and antiprotons are accelerated to almost the speed of light before they „shoot“ onto the matter or biological cell samples to be examined in the experiments. The three-part open-cut structure with supply, technical, and accelerator tunnels and the buildings immediately adjacent to it are built in a particularly solid way: The base plate of the tunnel segments, which extend to a depth of 17 metres (58 ft.), measures up to 2 metres (6.5 ft), and the extremely densely reinforced floor and wall segments with thicknesses of up to 6 metres (20 ft.) were constructed in special concrete according to an especially developed concrete formula. For the ring accelerator closed in mid-2021 plus auxiliary structures alone a total of around 315,000 m³ (412,000 yd³) of concrete was used in over 100 large-scale concreting works. Till the planned completion of all structural works in the middle of 2024, the entire FAIR project will require more than 600,000 m³ (785,000 yd³) of various concrete mixes for more than 20 building complexes above and below ground and the intricate bored pile foundation.

Concrete from a single source

Due to the high demand for concrete, the client FAIR GmbH and the responsible general contractors Porr Deutschland and Arge Züblin/Strabag have been relying on efficient on-site production of a total of almost 30 concrete types throughout the entire construction period. Since mid-2018, the company Mobile Betonkonzepte GmbH (MBK) has been responsible for the entire concrete logistics, from supply and storage of a wide variety of aggregates to transport and delivery by truck mixers and concrete pumps to the constantly changing building sites on this large construction area. As with all major MBK projects, the internationally active specialists are using the Euromix supermobile mixing plant technology made by SBM Mineral Processing also in Darmstadt.

Since its foundation, MBK has relied on the supermobile mixing plant technology made by SBM. Today, the plant fleet comprises a total of 18 Euromix plants with a hardened concrete output of 80 to 175 m³ per hour (105 – 230 yd³/h). Due to their modular aggregate bunker and silo capacities, the trailer-mobile plants offer full flexibility when equipping short-term construction sites through to large-scale projects with documented daily peaks of over 2,000 m³ (2,600 yd³) of concrete per plant. The still unique integrated design of the central Euromix mixing trailer with efficient insulation and powerful heating/cooling systems not only guarantees year-round operation even under extreme conditions, but also ensures that this top high-tech equipment, which can be easily adapted to new developments, retains its value for many years thanks to its premium-quality workmanship.

Proven systems engineering

MBK plant manager Mirko Thiele coordinates a total of three Euromix plants on the FAIR mega construction site. Since May 2018, two plants Euromix 3000 and 3300 have been working as a combined twin plant in the northern area where the accelerator tunnel, technical infrastructure, and aboveground and underground structures are located. Since the end of 2020, a Euromix 4000 has been in operation in the southern area with another 12 structures. Quality is a top priority: After the mixing plants were installed, the specifically defined special concrete with slow-setting blast-furnace cement and heavy, abrasive basalt grains was particularly subjected to 1:1 test concreting. Another focus is on temperature management in the mixing process: Depending on the ambient conditions, this is ensured by hot-air heating for the aggregates or nitrogen cooling for the cement and binding agents. During ongoing operation, MBK monitors the properties of the concrete types supplied with its own on-site test laboratory.

The special advantages of the Euromix concept from SBM Mineral Processing are particularly evident in the twin plant with its combined hardened concrete output of up to 275 m³/h (360 yd³/h) from its 3.00 m³ (3.9 yd³) respectively 3.33 m³ (4.3 yd³) DKXS twin-shaft mixers from BHS. Positioned directly next to each other and „mobile“ via a central control station in one-man operation, both plants have five separate cement silos each as well as their own aggregate stores, each with 8 types of aggregates, due to the large variety of concrete mixes required. The arrangement of the aggregate stores (2 x 252 m³ (330 yd³), in total around 650 tons) at a 90° angle to the mixing plants means that material delivery and material removal by truck mixers are clearly separated resulting in major logistical advantages especially for large concrete tonnages with cubatures of up to 6,000 m³ (7,850 yd.³) in multi-shift continuous operation. Around 8,000 tons of aggregates are stored directly in the area of the mixing plants – according to plant manager Mirko Thiele, aggregate deliveries reach a total of 18,000 to 20,000 tons per month. With daily peaks of up to 4,000 m³ (5,250 yd.³) of concrete, which are transported directly to the installation sites by truck mixers and concrete pumps, the Euromix twin plant achieved a total output of over 436,000 m³ (570,000 yd³) of concrete by the end of 2023.

Until today, the plant Euromix 4000 operating in the FAIR southern area since October 2020 has produced around 118,000 m³ (155,000 yd³). With a 4.0 m³ (5.2 yd³) DKXS BHS twin-shaft mixer, it achieves a hardened concrete output of max. 175 m³/h (230 yd³/h), while the actual daily peaks in Darmstadt reach a good 3,000 m³ (3,900 yd³). Euromix 4000 is also designed for a wide variety of concrete mixes with six connected cement silos and an aggregate store for six grain sizes. Like the combined plants in the northern area, it has an integrated residual concrete recycling unit, which in a controlled way recycles residual batches and the truck mixer wash water and thus further optimises the material flows on site.

Short distances and high availability

Mirko Thiele has been working for MBK in mobile operations for over 13 years and emphasises the great advantages of the flexible, modular Euromix concept made by SBM Mineral Processing especially for the FAIR project: „We were able to adapt our technology precisely to the required concrete quantities and types already in advance. In addition to the bare output rates, smooth construction site logistics is particularly important, which is essential here in Darmstadt due to the sophisticated construction requirements and the large number of works running in parallel.“ Despite the comparatively good transport connections of the mega construction site in the north of Darmstadt, the alternative supply via external delivery plants always involves a certain risk of failure, especially when it comes to extremely quality-sensitive and large concrete quantities. „With a maximum distance of 500 m (550 yds) there and back, we guarantee ‚just-in-time‘ delivery, and our optimised material logistics system significantly reduces the transport emissions and burdens for the surrounding area and the environment.

Of course, availability and smooth operation were particularly crucial for the more than 100 large concreting works – such as base plates up to 25 m (80 ft.) long, or equally long and – at 2.50 m (8.2 ft.), thickness and 4.50 m (15 ft.) height – no less massive wall segments. Thanks to the highly automated Euromix production plant (1 plant operator + 1 wheel loader operator), 6 to 10 MBK employees sometimes supplied a fleet of up to 18 truck mixers in multi-shift operation. Without any significant adverse effects due to extreme weather conditions: „In the Rhine/Main region, -10° C (14° F) has been the maximum so far, but the plants we use here have already proven themselves at much lower temperatures.“ According to Mirko Thiele, the plants Euromix 3000 and 3300 operating in combination have been part of the MBK fleet since 2010 respectively 2016, while the more powerful Euromix 4000 was newly acquired for the FAIR project in late 2020.