A tendency of the competitive Middle East construction industry has been to think rather short term; looking at initial costs and leaving the maintenance burden to future generations — particularly in the construction of bridges.
However, the ‘cross that bridge when you come to it’ attitude (excuse the pun) is becoming a thing of the past, with money and expertise being poured into large, iconic structures throughout the Middle East region.
“The designs are becoming extremely complicated and the structures are growing in size. Consequently, the investments are enormous and there is an increasing understanding that these structures should be maintenance free for many years. Not only from a financial point of view, but also because traffic loads are increasing and the inconvenience of closing these large structures for repair or maintenance will not be tolerated by the public,” says Arminox Gulf FZCO general manager Torben Krebs.
Arminox is a specialised service provider, which assists in the design of structures and acts as a consultant to ensure the intelligent use of stainless steel reinforcement. Stainless steel does not corrode and is therefore placed in the splash zone of a bridge or marine structure, where chlorides would attack carbon steel.
Carbon steel in these conditions would start to corrode within a few years and large amounts of money must be spent on repairs throughout the lifetime of the structure. Using stainless-steel reinforcement is likely to eliminate the cost of maintenance, according to Arminox.
Smart solutions
By ‘intelligent’ use of stainless steel, we mean ‘sparing’; stainless steel is an expensive commodity compared to carbon steel, so it is important to substitute the carbon steel with stainless steel only where it is needed. Kreb says that in a normal bridge structure, only 3-5% of the carbon steel needs to be replaced with stainless steel. This will ensure a 100-plus years’ maintenance free lifetime. The first structure using stainless steel reinforcement was a pier built in Mexico around 1940. This structure is still in use and has reportedly never received any maintenance works. We’ll have to wait another 30 years to see if it can meet its 100-year maintenance-free lifetime guarantee, but it looks promising. And with this in mind, more economical alloys have been developed over the past decade, which has seen the use of stainless steel reinforcement become commonplace across Europe, with the rest of the world catching on.
In the Middle East, Arminox has provided modern stainless-steel reinforcement solutions for projects such as Sheikh Zayed Bridge in the UAE, Pearl Qatar bridges and Sitra Causeway in Bahrain. It is currently looking into a number of projects in the region, including Qatar-Bahrain Causeway and Sheikh Jaber al-Ahmed al-Sabah Causeway in Kuwait.
In fact, Arminox says the worldwide consumption of stainless steel is expected to have increased from 5000 tons in 1995 to reach more than 500,000 tons by 2015. And bigger bridges do not just require smarter steel solutions; the more sophisticated use of ready-mix concrete is required.
Tried and tested
Like Kreb, Denis Beaupre, operations director for technical, sales and research and development at Unibeton Ready Mix, says an increasing number of clients are looking for long service life, which is usually achieved by controlling the corrosion of reinforcement.
“This has led to the production of very low water/cementitious ratio concrete combined with the use of supplementary cementitious material such as slag, fly ash and silica fume. The use of new-generation super plasticiser (polycarboxilate type), and sometimes corrosion inhibitors, have made concrete more durable, but also more susceptible to early cracking,” according to Beaupre. “Use of synthetic structural fibres might be a good solution to provide the whole system with protection of the main reinforcement. “Of course, the use of post-tensioning can reduce the total area where concrete is under tension and thus susceptible to develop surface cracks that may affect the real service life. These parameters are difficult to control and even more so to predict,” he adds.
Beaupre says the Middle East also demands tough durability (rapid chloride permeability for example), for controlling concrete temperature and workability during the hotter months.
The company has witnessed trends such as the ongoing use of self compacting concrete in the GCC, IBB workability probes for quality control, iCRETE systems for optimisation of mixture design and QAQC control at batching plants.
Furthermore, varying cement prices in the UAE mean it is difficult to set the raw material price for more than 12 months from the start of the project, says Beaupre. “We make sure we have a batching plant nearby. During the last cement crisis, Unibeton was able to supply all its customers because of our good relations with suppliers,” he adds.
The company has serviced a number of bridge projects in the region; it provided more than 240,000m3 of concrete with high slag content, incorporating calcium nitrate as corrosion inhibitor, pumping services, and self-compacting concrete for high congested/ non-accessible parts of the Sheikh Zayed Bridge in Abu Dhabi.
For the Sheikh Khalifa Bridge linking Abu Dhabi and Saadiyat Island, Unibeton Ready Mix supplied up to 140,000m³ of concrete, piling with set control to allow barging and early high strength concrete.
The new Garhoud Bridge in Dubai required 150,000m³ of concrete with GABS and silica fume, pumping services, and low heat of hydration concrete for the raft supplied at 25°C in summer. In addition, Unibeton tells The Big Project that it is currently commencing piling and foundation work on Hudayriat Bridge in Abu Dhabi. In conclusion, Kreb suggests: “If a life-time cycle costing exercise was obligatory in all large projects in the Middle East, we would see a rapid change for the better”.
FIVE BIG BRIDGE PROJECTS IN THE PIPELINE
1Bahrain-Qatar Causeway
This US $3 billion Qatar-Bahrain Causeway is a 40km two-lane dual carriageway linking Qatar and Bahrain and being developed by the Qatar Public Works Authority and the Bahrain Ministry of Works. The road will run over 18km of embankments where the sea is shallow and 22km of viaducts and bridges over deep water, including two 400m cable-stayed bridges over shipping channels.
2Subiya Causeway
The Ministry of Public Works in Kuwait is developing this $3.7 billion causeway, which will stretch approximately 37km across the Bay of Kuwait connecting Shuwaikh Port with Subiya New Town Development. As part of the project, a 27km low-level bridge across the bay, a main bridge spanning 200m, an elevated road and a 5km approach road onshore in Subiya will be constructed in phases.
3Hudayriat Bridge
Abu Dhabi’s $50 million Hudayriat Bridge is being developed by the Tourism Development and Investment Company (TDIC) and will connect Hudayriat Island with the capital’s mainland.
4Sheikh Zayed Bridge (Business Bay Canal Extension — Phase one)
Dubai Roads & Transport Authority (RTA) is spearheading the extension of the Business Bay Canal. Phase one involves elevating Sheikh Zayed Road above the canal to form a bridge stretching 800m.
5Sheikh Rashid bin Saeed Crossing (sixth crossing)
Designed to be the longest arch bridge in the world and largest single road project, the Sheikh Rashid bin Saeed Crossing being developed by Dubai’s Roads & Transports Authority will be 1.7km long, 64m wide and positioned 15m above water level. It will comprise 12 lanes, a rail track and hold Dubai Metro’s Green Line. The bridge will have a capacity of around 20,000 vehicles per hour and will link Al Jaddaf and Business Bay at Bur Dubai. The giant arch of the bridge will peak at 205m and will be 667 long. The project also includes 12km of new roads and 22 intersections in surrounding areas.