SIKA was a sole supplier of 14,000 tonnes of concrete admixture for Dubai Metro

CONCRETE: DUBAI METRO

PROJECT DESCRIPTION
The Dubai Metro is a driverless, fully automated metro network. The phased opening schedule began with the inauguration of the first phase of the ‘Red Line’ in September 2009 and additional line and station openings will continue until 2020 and the full 320 km network is completed.
These first two lines that are nearing completion have elevated sections for 58.7 km and underground sections in tunnels for 12.6 km.
The tunnels were created with Tunnel Boring Machines (TBM) and lined with more than 53,000 precast concrete tubbing segments, produced with more than 130,000 m³ of high performance concrete.
The elevated sections were built using prestressed segmental bridge construction techniques, from huge precast concrete units approximately 10 m wide by 4 m long and weighing more than 80 tonnes each. The 17,000 precast units required more than 700,000 m³ of high performance concrete.

PROJECT REQUIREMENTS
Tunnel Tubbing
The tunnel tubbing segments had to be produced in an automated process including steam curing in order to meet the rapid delivery requirements. The concrete quality and surface finish had to meet high specifications, plus to maintain the required production rates; a high early strength in excess of 10 MPa within 12 hours was demanded.
Bridge Elements
The large precast bridge units had additional uniform visual appearance demands, plus the concrete had to maintain a high slump of over 150?mm with good consistence, for more than an hour; followed by early strength development to facilitate these units’ rapid handling and erection.
The ultimate compressive strength for these units was specified to be 70 MPa and this had to be reached with a low water : cement ratio
Diaphragm Walls and Underground Stations
The total concrete volume for the construction of the diaphragm walls and underground stations added up to approximately 150’000 m³ for the ‘Red Line’ and 220’000 m³ for the ‘Green Line’. The most challenging requirement regarding these concrete mixes was the extended workability of the fresh concrete of 3 to 4 hours. The long transportation time was caused by the expected traffic jams in the vicinity of the construction sites and the two transfer stations.

SIKA SOLUTIONS
Sika’s Concrete Technologists worked closely with the project engineers to execute an extensive testing programme and develop special concrete mix designs for both the tunnel tubbing segments and the segmental bridge units.
For the tubbing segments a slump of 150 mm for over one hour, follo-wed by high early strength development to over 10 MPa was achieved, which allowed the production cycle to be repeated twice a day, effec-tively doubling normal production rates.
The concrete mix design for the large segmented bridge units was adapted to maintain an extremely high slump of 215 mm for over an hour, even at the specified ed excellent flow and compaction around the congested steel rein-forcement, plus minimal surface pores and resulting in the desired uniform surface finish and excellent visual appearance.
All of these concrete mix designs for the project were achieved using Sikament® NN (Sikament® NNS in the very high summer temperatures, frequently in excess of 35º C) and other compatible Sika Admixture Technologies, to meet or exceed all of the Precast Concrete Producers and the Project Consulting Engineers requirements on this prestige project.
The solution for the diaphragm walls and underground stations was the application of Sika® ViscoCrete®-3110 with an extra-ordinary low dosage of approximateIy 1.1 % by weight of total binder.

CONCLUSION
The Dubai Metro will be a great step forward to improve the transportation system of one of the world’s fastest growing cities. Despite the above mentioned concrete types, all the other concretes delivered by Arabian Mix are produced with Sika admixtures, namely Sikament® R4QV and Sikament® R4QV CD. This means Sika provides a concrete admixture system that is covering the whole range of concrete grades and technical requirements. Finally Sika UAE, being the sole supplier of 14’000 tonnes of concrete admixtures is an important and reliable partner for this ambitious construction project.
 

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