ADJUSTABLE-radius trapezoidal girder formwork (TTR) from Paschal, a premier German formwork specialist, is being used for the first time in Saudi Arabia for the construction of 24 circular tanks in Dammam.

The project is part of an extensive expansion of an existing wastewater treatment plant being implemented by the Saudi Ministry of Water and Electricity to cope with the requirements posed by Dammam’s rapid population growth.

The contractor entrusted with this task, SysTech (Riyadh branch), began the shell construction works last December.

he new structures will be located on three sites. Each of these will include two big aeration tanks (98.5 by 56.7 m footprint) with six coils across a width of 9 m into which the waste water is conveyed. Besides these, there are four circular tanks (external diameter 39.9 m with a wall thickness of 40 cm), two smaller circular tanks (external diameter 33.6 m) as well as conventional technical rooms.

Eight circular, in-situ-cast concrete structures will stand on a footprint of approximately 400 by 500 m. The entire project will include the same facilities on three construction grounds of about 60 hectares involving a total of 24 circular structures. Approximately 200 men will work on the construction site from 2013 and the structural works will be completed in phases.

All foundations have already been laid and many straight walls are currently being raised, as the formwork enters service on the construction site. “A German supervisor has instructed the teams how the formwork can be installed on the corresponding circular footprint on site and has shown them some techniques to facilitate their work. The circumference was determined precisely to the centimetre by means of the equipment provided on site,” says a spokesman for Paschal.

Three different radii were used for the construction of the aeration tanks.

For the 4.95-m concrete height, segment heights of 3, 1.5 and 0.75 m were used, that is a framework height of 5.25 m. These segments remain in height and will continue to be used. “Assembly, installation and realisation proved to be surprisingly easy,” he says.

“The quantity of tie points is very low when compared with rival systems and the formwork thus needs no adjustment and no final matching of the finished construction profiles. Even though the circular formwork is a completely new technology for the team, a whole work cycle can be completed in just two days, representing a surprisingly fast construction/site time.

The aeration tanks have an inner radius of 8.45 m, 9.15 m or 4.5 m. The external circular walls are conical with a wall thickness of 60 cm at the base and 30 cm on top. For this reason, some steel filler pieces were manufactured in Paschal’s main plant in Steinach. These are compatible with TTR and can be locked in using bolts.

The spokesman continues: “TTR is an amazing technology in terms of handling, strengths as well as advantages for construction managers. It was developed with this kind of construction work in mind. This is a fast, easy and system-integrated solution to a challenging task.”

“The TTR is made of a 21-mm strong, 15-layer nail-on Finnish birch plywood. This is the only system, which can be flexibly bent up to a radius of 2.5 m, while other types of plywood with a similar thickness would break or form waves.
“As a so-called ‘double girder segment’ (a segment with two longitudinal beams), this formwork can handle radii of up to 1 m with 18-mm-thick plywood.

This makes the formwork steady, completely round and exact without any deformation, even in case of reuse. The circumference can be determined to the centimetre and with no final adjustment of the construction profiles. Although there are only 0.28 tie points per sq m, 1 sq m of formwork can bear up to 60 kN fresh concrete pressure.

“It is precisely these advantages that come into play when facing challenging technical constructions in both high-quality architecture and in the case of these circular tanks.”

“Thanks to the fast installation processes and the incredibly low number of tie points as well as no requirement for further rounding or additional support/belts, the entire formwork-making process was practical, safe and fast. In short, it is the best and most efficient system currently available. Moreover, the low number of tie points has increased the quality of the concrete surface,” he says.

The parent company Paschal-Werk G Maier, founded in 1964, is an international company specialising in concrete shuttering, propping systems and formwork engineering software.

The Paschal product range comprises systems for modern wall and ceiling formworks, special shuttering, climbing formwork and scaffolding decks, load-bearing scaffolds and propping as well as dedicated, customised software systems for concrete construction planning, organisation and management. The company has achieved DIN EN ISO 9001 certification for the quality of its products.

To provide enhanced services and following several years of operations in the Middle East, Paschal opened its Middle East branch in 1998 in Bahrain.

“Paschal’s cost-effective and environment-friendly formwork systems have become popular among companies in the Bahrain and other countries in the region, which are aware of its advantages,” says Amir Delghandi, general director of the Bahrain-based Paschal Concrete Forms Company.

Besides the cost advantage for the contractors, there is also an environmental benefit of using Paschal products. Many contractors in the region have been able to see for themselves the durability Paschal formwork – 1 sq m of this formwork replaces 100-sq-m plywood and 5 cu m of timber, he adds.

To meet the growing demand and provide clients with a more professional and efficient service, Paschal built its own 3,200-sq-m facility over a plot of 5,600 sq m at the Bahrain International Investment Park (BIIP) in Hidd and has been operating from this new office since June 2010.