Concrete: Complex challenges
By Helen Wright14 October 2011
Demand for ready mixed concrete fell 5.9% in the EU last year, according to the latest figures from the European Ready Mixed Concrete Organisation (ERMCO), but the pace of the decline has certainly slowed compared to the 20.8% slump in production seen from 2008 to 2009.
This tentative recovery is likely to continue – worldwide cement consumption is forecast to reach a record 3.9 billion tonnes by 2012, according to UK-based International Cement Review in its latest Global Cement Report.
But while the recovery in mature markets is expected to be slow compared to the boom in demand from developing economies, there is no shortage of challenging construction projects driving innovation in Europe.
From new batching plants to devices for testing the integrity of concrete foundations, the latest product launches and applications for the European market are defined by their push to overcome increasingly complex technical challenges while delivering higher quality and fast production cycles.
In Slovakia, for example, a large infrastructure project is underway to extend the R1 dual carriageway between Nitra and Banská Bystrica.
Hungarian bridge-building specialist A-Híd Építő was drafted in to close one of the last gaps in the new road with a 1.2km bridge. High adaptability and short cycle times were a must for the superstructure to be completed on schedule.
The contractor selected Doka cantilever forming travellers (CTFs) for the project. Because of the large 26m width of the deck, the Doka bridge specialists designed the CFTs with four longitudinal trusses – a modular design it said allowed cost-effective adaptation to unusual cross-sections.
This made it possible to minimise the amount of equipment needed and ensure rapid cycling. A-Híd Építő supervisor András Gyalog said the company had been impressed with Doka’s cantilevering technology.
“The construction progress was very successful. The plan was 10 days per section. The best result was seven days per section, and the average was eight days.
"Also, the pre-assembly only took ten days, so Doka’s CTF definitely saved us a lot of time,” he said.
Formwork and falsework manufacturers are focusing on ways of enabling new builds using concrete to complete as quickly and efficiently as possible, no matter how complex the task.
Another example is Peri, which provided a comprehensive formwork and scaffolding package for the construction team working on the Prosta Tower in Warsaw, Poland.
This helped contractor Warbud finish the structural work in only 11 months.
For constructing the reinforced concrete facade of the 70m tower, Peri’s Trio was used – a 6m high system that is said to be simple, inexpensive and quick to assemble.
Meanwhile, double-layered formlining provided virtually joint-free concrete surfaces using Peri’s Fin-Ply Maxi formliners.
Peri also used a continuously extended working scaffold that moved in line with the building progress to support construction. The company said this made a significant contribution to maintaining the construction schedule as well as increasing safety levels for site personnel.
Peri said the inner-city location of the build meant that there was no available storage space, and the fact that the site had only one crane also made logistics operations complex.
“Implementation of the architectural requirements was extremely demanding and the building with the filigree reinforced concrete web seems anything but straightforward and simple,” Peri said.
In Germany, meanwhile, Meva supplied its KLK 230 climbing formwork for the renovation of the Klingenberg dam, which was built in 1914 and damaged during floods in 2002.
The company’s engineers designed and constructed a special adapter beam that could be mounted to anchors set into the dam. The curve of the face meant that the anchors were not always parallel, so the beam had to be able to cope with these tolerances.
The work involved sealing the dam’s upstream face and installing new drainage systems.
This meant adding four layers of material, a 400mm to 800mm layer of concrete to even out the stone surface, followed by a bitumen foil to allow this equalising layer to move independently of the sealing layer. This was then followed by a 130mm thick course of hollow drainage bricks, and then a 400mm thick layer of sealing concrete.
Control and fine-tune
Site manager Marko Würker, of main contractor Züblin, said, “Thanks to the special design of the climbing formwork units, we were able to work in parallel and perform several jobs at the same. This has enabled us precisely to control and fine-tune all work steps during the complex renovation.”
Flexibility is also central to meeting the special requirements of suppliers when it comes to concrete mixing plants. German concrete supplier Neuland Beton, for example, recently commissioned a Stetter HN 3.0 horizontal mixing plant in Hamburg, replacing a competitor’s plant.
In addition to generally standard equipment, such as forced dedusting, cameras, and additive handling, which can be combined and matched according to individual preferences, the Stetter HN 3.0 comprised a concrete inline silo with seven chambers, and an active storage volume of 1,200m³, plus a daily production capacity of 800m³ of compacted fresh concrete.
Stetter said the flexible modular concept of the plant enabled it to be tailored precisely to meet customer requirements. The HN 3.0 is controlled using a Stetter MC400 control system, which can accommodate flexible expansion options and special user preferences.
In this case, Neuland Beton asked for a barcode reader to be incorporated for the delivery of gravel – when the barcode is read, the aggregate delivered from the source hopper is automatically assigned to the appropriate chamber in the inline silo.
Modern components in cement plants can also provide significant efficiency gains. This year, for example, HeidelbergCement replaced three old mixers at a ready-mixed concrete plant in Amsterdam with one new BHS-Sonthofen DKXS 4.50 twin-shaft batch mixer – a move that reduced energy and maintenance costs while increasing output.
It said that thanks to growing demand, the supply capacity of the Amsterdam plant had to be increased. However, its management wanted to avoid a complete demolition and reconstruction, and instead opted for a fundamental overhaul of individual central components.
At approximately 40 mixing trips per hour, with a discharge of 5m³ suspension and 4m³ gravel per batch, the new mixer attains a hardened concrete capacity of 360m³ per hour – 4.5 times the rate of the old plant capacity.
The DKXS 4.50 is planned to produce 125,000m³ of concrete in the first year after modernisation, using a workforce of only three.
Wacker Neuson provided another example of bespoke modification when it installed 90 AR75 Vario high frequency external vibrators for FP McCann, a UK manufacturer of precast concrete tunnelling and drainage systems.
FP McCann needed to expand production at its Cadeby factory in Leicestershire to accommodate an eventual total of some 150 extra precast moulds, all fed from an on-site concrete batching plant via an overhead bullet system.
The AR75s were bolted directly to each side of every mould and are set to run for approximately five to ten minutes per pour. In addition, each motor can be adjusted to operate at any speed between 0 and 6,000rpm, via special inverter panels, to enable an optimum combination of compaction consistency and low noise.
To cope with the rigours of this harsh environment, which involves the use of a steam system to speed the curing process, all the vibrators have been specified to be steam resistant – the first time that Wacker Neuson has supplied this option in the UK. All hardware such as screws and bolts were zinc plated, and extra seals were fitted.
A raft of new products for concrete construction has also been brought to the market this year. Chinese manufacturers Zoomlion and Sany are targeting the European market, for example.
Both unveiled new models of concrete pumps and placing booms at the Samoter exhibition in Italy, while Sany has opened a €100 million manufacturing factory in Bedburg, Germany, to manufacture truck-mounted pumps, stationary pumps and concrete batching plants.
Sany also presented its first 30m class RZ five-section concrete placing boom at the Samoter show. Coupled with a SYG 5260 truck-mounted concrete pump, the boom can be mounted to standard three-axle chassis as well as four-axle trucks with wheel bases as narrow as 2.3m.
Sany has also redesigned the boom’s self-supporting, stress-free sub-frame with X-shaped outriggers in front, and straight outriggers in the rear.
Zoomlion, meanwhile, unveiled a new 33m truck-mounted concrete pump – the Zl33 – targeted at Europe, at the Samoter show. It is a Z-fold unit produced in China and assembled by Zoomlion’s Italian subsidiary Cifa, which offers parts and services for both the Cifa and Zoomlion ranges via its dealer network.
April’s Kommatek show in Turkey saw the company unveil the 37m 37X-4Z, mounted on a Volvo chassis. Again, it is a Z-folding boom, offering 120m3/hour of output and pressures up to 70bar – the same characteristics as the ZI33.
New devices for testing the integrity of concrete once it has been placed have also been launched, including Elcometer’s new P331 Covermeter.
This is a device for revealing what is going on beneath a concrete surface, using a pulsed electromagnetic field to provide the location, orientation and sizing of reinforcement bars, as well as the depth of concrete cover within structures.
The P331 has new features, including data logging and analysis using a software package, in addition to the ability to take new measurements to determine the likelihood that corrosion is taking place.
It can be used by contractors to prove the quality of a new build, including confirmation that the reinforcement bars have been correctly positioned and are covered by the appropriate depth of concrete.