DYWIDAG Strand Tendons for new Silos: Expansion of the Qatar National Cement Company Production Facility
Founded in Qatar in 1965, Qatar National Cement Company (QNCC) is a major producer of Portland cement, sulphate resistant cement, hydrated lime, calcined lime, washed sand and clinker. QNCC has set itself the target to increase its annual cement production in order to satisfy the increasing demand for construction projects due to the Soccer World Cup that will take place in Qatar in 2022.
For this reason, QNCC awarded the FIVES company with the contract for the construction of a 5th production line in the town of Umm-Bab in western Qatar that will have a capacity of 5,000t of clinker per day once completed.
The new production facility also required the construction of 4 silos (two cement silos, one raw meal silo, one clinker silo) that were post-tensioned using loop tendons. DYWIDAG-Systems International GmbH, GBU, Germany proposed a special solution to the planners Peter and Lochner that consisted of changing the planned tendon types 7-0.6", 9-0.6" and 13-0.6" to uniform Type 7-0.62" DYWIDAG Strand Tendons with SD Plate Anchorages and Type 12-0.62" Post-Tensioning Systems with MA Anchorages. By reducing the tendon sizes, the number of required stressing jacks could also be reduced. The horizontal tendons were simultaneously stressed using two jacks.
For the two new, 72m high, 35m Ø cement silos, DSI Middle East produced and supplied 162 Type 7-0.62", 39m long DYWIDAG Strand Tendons per silo with a total strand tonnage of 102t.
In the 86m high, 32m Ø raw meal silo, 112 Type 12-0.62", approximately 38m long DYWIDAG Strand Tendons with a strand tonnage of 57t were used. In the 46m high, 51m Ø clinker silo, 52 Type 7-0.62" and 76 Type 12-0.62" DYWIDAG Strand Tendons in lengths of approximately 54m and with a strand tonnage of 81t were installed.
The installation of the anchorages for the two cement silos that were built using the slipform construction technique had to be carried out shortly after the SIAC company awarded the contract to DSI Middle East. All of the parts that had to be imbedded in the concrete were shipped from Germany via air freight. The SD Plate Anchorages according to ETA 13/0815 had a decisive advantage in comparison to MA Anchorages: For the SD Anchorages, only a lightweight plastic trumpet had to be installed before concreting because the heavy steel component of the SD anchorage is only required at the time of stressing.
Due to the low weight of the required plastic trumpets, the additional cost for air freight was low. Since the steel anchorage plates were only needed later on, they could be shipped via sea freight from DSI’s central warehouse in Langenfeld to Qatar.
The installation of the DYWIDAG Strand Tendons including post-tensioning was successfully completed within 9 months’ time.