Mobile revolution

24 April 2008

This year's intermat exhibition saw concrete equipment manufacturers display a wealth of new equipment. However, with the absence of the major formwork manufacturers - Meva, Doka and Peri - most of the new products on show tended to be pumps, placement booms, batching plants and truck and static mixers.

Italian manufacturer Cifa, for example, showed three new truck mixers, the SL7, 8 and 9, alongside truck mounted concrete pumps and booms, K41 XRZ, KL37 and K52 L. Also on its stand were the Compact, Personal and Cifamix mixing plants and its ConmpactEasy batching plant. There were also new versions of its Spritz System, the CSS3, for tunnels and KT placing booms for high rise construction. According to Sebastian Buca, project manager, the later is proving extremely popular in Dubai, China, India and Latin America.

Another Italian company enjoying considerable success in Latin America is Fiori. The company was using Intermat to launch its Mixer 4000, an extremely compact truck mixer for cramped construction sites. Andrea Bonomi, export area manger, told CE that besides Latin America the truck is also proving popular in Northern Europe.

Italy-based Imer also launched a slew of products at Intermat, including its ORU Oneday 2250 and ORU Logik mixing plants and its ORU MT turbo- planetary mixer. Also on its stand was its new SL - super light - truck mixer.

The company has recently announced plans to invest € 3 million in a new production facility in Akasaray, Turkey. A move Imer president Silvano Bencini said was designed “to grasp all the opportunities offered by a market with excellent development potential.”

The news comes on top of a rise of +22% in exports in 2005 and a +6% rise in sales to € 177 million for the company.

Right Mix

However, it was not just Italian companies that launched new equipment at Intermat. Germany- based Putzmeister showed its new truck mounted 61 m reach M 62-6 pumps two of which have been used by concreting sub-contractor Necso for construction of two 52 m high liquid natural gas (LNG) storage tanks using cryogenic concrete in Mugardos, Spain alongside its established M 63-5 (62 m reach) and M 58-4 (57 m reach) pumps.

The tanks sit on 80 m diameter, 1,6 m thick podiums, which consist of 5500 m3 of high-strength concrete and are reinforced with over 830 tonnes of steel. However, because the gas in the LNG tanks has to be kept at a very low temperature, -161°C, the tanks must be completely sealed against leaks and insulated against rises in external ambient heat. In extreme cases, the external wall of pre-stressed concrete must provide a tight seal around the liquid gas, and, in case of a rupture withstand pressure as the liquid boils off.

Therefore a double insulating wall of concrete - an inner and outer shell - is needed in order to maintain the required temperature to store the gas. Lining the base and walls of the inner shell is a special steel alloy with modified carbon content, while the ceiling consists of an aluminium-nickel alloy.

A layer of perlite (naturally occurring glass) and insulating fibres covers the inner walls. The inner shell surrounds the gas tank, which is made of a steel-nickel alloy.

Necso constructed the two 42 m high, 0,75 m thick external shells from high-strength pre-stressed concrete. Rising 3 m every 15 days the tanks took 210 days to complete using sub- contractor Bombeos Payosaco's Putzmeister M 33-4, M 36-4 and M 46-5 concrete pumps (33, 36 and 46 m reach respectively).

Roof Construction

Once the walls had been completed the tanks' roofs could be constructed. This, according to Necso project manager Alberto Curto, was one of the hardest parts of the project.

Necso rented six Putzmeister truck mounted concrete pumps, with vertical reaches of up to 63 m. Technicas de Bobeo y Gruas (TBG) provided an M 63-5 and M 58-4, Transportes y Bombeos Bedmar provided two new M 62-6s and Ruyma Bombeos de Hormigon provided two M 58-5s.

During operation the six pumps were arranged equidistantly around the tanks' base. According to Mr Curto it was important to achieve equal distribution of the “wet on wet” concrete so the M 58, M 62, M 58, M 63 etc. were placed alternately, which allowed a uniform coverage throughout the concreting.

Once the edge reinforcement was complete the pumps were attached to one of four Putzmeister RV 10 concrete placement booms, arranged equidistantly on the tanks' roofs.

Initially, Necso had allowed 36 hours continuous pouring per roof. However, careful scheduling of the concrete delivery saw the work completed in just 24 hours.

About 40 truck mixers were used to enable continuous loading of the pumps from two mixing plants located close by. Work “corridors” were set up around the tanks so the truck mixers had easy and continuous access to the site.

About 3000 m3 of concrete was needed to cover each roof, which consisted of 900 tonnes of concrete reinforcement and 800 tonnes of pre- stressed steel reinforcement.

Road Expansion

Infrastructure requirements of a different kind have seen continued expansion of the motorway network along the border of Germany and the Czech Republic. Development of the Czech D 8 motorway and the German A 17 autobahn will create the new E55 European highway between Dresden and Prague.

As Part of the expansion, construction of a 1,08 km long motorway bridge, by Prague-based contractor Metrostav, on the outskirts of Aussig/Trmice is almost complete. Construction of the steel composite structure involved the first use of a formwork carriage in the Czech Republic.

The two carriageways, each of which sits on top of their own set of Y-shaped piers, range from 14,2 to 15,4 m wide. The piers, which can rise to about 27 m high, use two different wall thicknesses in the pier heads.

Construction of the rectangular pier shafts used Peri's Vario GT 24 girder wall formwork on CB 240 climbing brackets with concreting cycle heights of 5,7 m. With the CB climbing scaffold system, the formwork is moved with the scaffolding as a complete unit using a single crane, which, according to Metrostav, resulted in considerable time-savings.

“For cleaning the formwork, reinforcement work and installing the leading anchor, the formwork was easily moved thanks to the roller bearings on the carriage. The high ratio of re-usable parts, along with simple installation and dismantling, made the anchoring system extremely economical,” said a Metrostav spokesman.

Cost Savings

For the pier heads, which open upwards from a height of 7,25 m to form 9,75 m wide V-shaped structures, Periís Czech engineers developed a time and cost-saving formwork solution complete with suspended brace frames. However, due to the height of some piers and the weak load-bearing capacity of the ground, shoring could only be used to a limited extent.

Combined and horizontally placed brace frames, normally used for single-sided concreting for wall heights up to 8,75 m, served as load-bearing brackets. Their design, according to Peri, guarantees safe transfer of the concrete dead load, as well as any live and wind loads.

Lightweight aluminum, high load-carrying Multiprop slab shores and SLS heavy-duty spindles allowed accurate adjustment of the formwork and transferred the loads from the heads into the pier shaft. Filler boxes on the Vario elements meant the 1 m thick pier head shear walls and 2,35 m thick main support members were formed in a single pour. This saved time, increased productivity and meant the system could be moved easily.

Elsewhere, construction of the carriageway slab used two composite formwork carriages to cast 20 m segments. The design of the 22 m long carriage was such that it could be pulled along the bridge for 820 m before any re-assembly work was needed.

Lateral suspension, with a possible vertical adjustment of 600 mm, allowed for variations in height as a result of the changing cross fall. As the bridge widened in the centre, one formwork carriage was altered to handle casting segments from 7,50 to 8,25 m wide.

The formwork for constructing the carriageway's middle slab was connected to the Peri formwork carriage by means of tie rods. Once casting was complete the formwork elements were lowered onto the roller bearings, the internal filler elements removed and the whole system moved to the next casting segment.

High-Rise

While infrastructure in Eastern Europe continues to expand, so does the high-rise construction sector. In the Estonian capital of Tallin, for example, main contractors Merko and Kontek are currently erecting a 112 m high residential and hotel tower.

With just 11 months for construction of the tower's shell a streamlined in-situ concreting workflow coupled with safe working conditions was called for. To meet the deadline Merko and Kontek chose Doka's GCS wall formwork guided climbing system with its built-in windshield. According to Doka's project manager Hannes Stolzlechner, the windshield screens off the slab-edge zones on three storeys at a time. This improves safety and means the crews can work unhindered by the weather.

“For the exterior walls”, said Mr Stolzlechner,“the GCS system can be used in just the same way with our Top 50 wall formwork as with the windshield - for screening off the slab-edge zones. In other words, you can raise both the windshield and the wall formwork units together, using one and the same system”.

This, added Mr Stolzlechner, simplifies assembly and speeds up repositioning operations, which saves time and money while increasing productivity.

“When you have to climb 33 storeys, like here on the Tornimäe project, it pays to use the Windshield system on every storey”, said Mr Stolzlechner. “After all, you only need to erect it once, and then all you have to do for the climbing operation is get the crane to pull it up.”

In order to get the floor-slab formwork equipment up to the top storey of each tower quickly and easily, two wheeling-out platforms per tower were integrated into the Windshield system. The stripped formwork is transported onto these platforms and lifted from there by crane.

However, according to Mr Stolzlechner, the Windshield system has done more than just enhance workplace safety, eliminate downtime and speed up the construction progress. Its 9 m high stair tower enabled the site crew to walk up to the top floor-slab in complete safety. This meant an external stair tower, which would have needed repeated vertical extensions, was not needed. Again, this saved time and money, while increasing productivity and increasing site safety.

Outlook

The continued development of longer, more flexible placing booms, re-usable formwork and modular, lightweight batching plants looks set to continue as contractors look to achieve both time and cost savings.

Healthy profits among manufacturers should also see investments in new manufacturing facilities and more money spent on research and development, which should also benefit contactors.            ce

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