The dry docks at the $611 million ship repair yard development at Ras Laffan Port in Qatar is expected to be used by 5000 ships a year by 2012, making Ras Laffan the world's largest hydrocarbon port. On track for completion in 2010, these facilities are being built to world class standards. Readymix Qatar, onsite supplier of possibly the most vital construction component – concrete - relied on the specialised solutions of BASF Construction Chemicals UAE to meet stringent engineering specifications.
The State of Qatar’s primary income derives from oil and gas exports, with its North Field estimated to hold 15% of the world's proven natural gas reserves. Marine vessels are the floating pipeline for these products. However, Qatar had minimal capacity for the repair, maintenance and construction of ships or the fabrication of offshore structures. This prompted the 2007 JV between Nakilat and Qatar Petroleum to develop these facilities at Ras Laffan Port.
Says John Sarkis, GM of BASF Construction Chemicals for the Middle East: “These facilities will not only support the natural gas (LNG) industry, but generally increase income to the region. However, this is a highly specialised industry. The vessels in use are highly specialised as the fossil fuels they carry are flammable and highly toxic to vulnerable marine environments. The design and construction of the Ras Laffan Port facilities thus had to meet strict standards, starting with the infrastructure and the most basic of construction materials – concrete.”
The port’s shipyard will be built on 43 hectares of reclaimed land. It will comprise two dry docks, one dock 400m long x 80m wide and the other 360m long x 66m wide, both with 12m of water over the sill. The design also includes one floating dock 230m long x 38m wide with a 20,000t lift capacity; a quay with six full length berths, totalling 2.4kms in length; a number of workshops with a full range of support facilities, such as machine shop, pipe shop, steel shop, stores; and other structures such as offices, amenities, a medical centre, fire station, facilities for ships' crew, etc.
The building of the LNG berths and the dry docks were prioritised in Phases I and II of the build strategy to enable repair of large ships, including LNG carriers, very large crude carriers and medium-sized vessels (20,000dwt to 80,000dwt); as well as conversion of tankers to floating, production, storage and offloading, and floating storage and offloading (FSO) units.
The building of these structures would require 900,000 cubes of concrete, made available at various rates and with differing characteristics. Explains Sarkis: “Besides the quay, there was the dry dock design to take into consideration. It includes a massive two-metre high concrete floor in a chequer board design, with a 12 meter breakwater wall calling for the placement of 80 CAISSONS – that’s 80 12,000m3 blocks of concrete.”
For each structure, engineering specifications were clear. “Marine structures are highly susceptible to corrosion, thus durability features strongly in concrete specifications. Specifically, concrete with a dense pore structure and high strength was required. For the caissons, for example, concrete expectations were 40 newtons with 20mm aggregate,” says Peter Latham, Technical Manager at RMQ.
The requirements of Daewoo Engineering and Construction Company, who in 2007 had been awarded the US $610.6 million contract from Nakilat to build the shipyard in Qatar, were for a readymix supplier with the experience and expertise to not only deliver concrete at the right time, in the right quantities, reliably, but to provide concrete of a consistent quality that met the rigorous standards set by design engineers.
When RMQ won this contract in 2008 based on its proven track record in Qatar working on prestigious projects such as Ras Laffan Industrial City and Mesaeed Refinery, it turned to long time partner BASF Construction Chemicals to resolve technical challenges.
Says Latham: “Besides meeting engineering specifications, we were dealing with three key challenges, namely the high ambient temperatures, difficult logistics and language barriers.
“The heat affects the workability and setting times of the concrete and, depending on what admixtures are used, also the strength of the final product. In terms of logistics, all the aggregates are imported and arrive by barge – admixtures and cement supplies also needed to be timely. In fact, there could be no compromise in overcoming logistics and language barriers as a key part of any build is having the right materials available when needed to meet schedules and deadlines. Having dealt with BASF Construction Chemicals on numerous large contracts, we were confident we could rely on them to assist us in not only getting the quality but also the ‘on-time’ part of the equation right.”
BASF Construction Chemicals proposed use of the following admixtures:
Rheobuild 857 - a high range, water reducing superplastiziser for concretes containing GGBS and microsilica, it provides good slump retention, good performance in high ambient temperatures.
Rheobuild 1100 – the synthetic polymers that make up this product allow mixing water to be reduced considerably and concrete strength to be enhanced significantly, particularly at early ages. This made it ideal for use in production of the Caissons, which required a concrete with high initial workability and high early strengths in order to advance the slipform.
Rheomac 730 – a hydrophobic pore-blocking ingredient (H.P.I.) for concrete that significantly reduces water absorption of concrete. It reacts with the cement hydration process to form a hydrophobic ingredient to reduce the capillary suction and prevent the ingress of potentially deleterious soluble material, resulting in concrete with enhanced durability – and watertightness. This product was used to reduce the water absorption of the concrete in all concrete cast below the water table.
Meyco SA430 – a high performance liquid accelerator that assists to achieve higher final strengths and more durable final product. Due to fissures in the rock bed allowing sea water seepage into the construction excavation, the contractor had to consolidate the bedrock with grout. This product was used to accelerate the setting time of the flowable sand cement and water grout.
Says Merlyn Heynes, BASF Regional Sales Manager: Admixtures Systems - Qatar: “Together with Readymix Qatar and the client we customised mix designs. In addition, we made use of local supply affiliates to ensure supply logistics matched the requirements of the readymix and construction teams.”
BASF Construction Chemicals’ was on hand on site to advise and assist with mix design and construction approaches.
The drydock is now about 80% complete, with completion set for November 2010. There have been no delays on the job due to concrete quality or supply. Quality of delivery has also been high. Says Latham: “We had to erect three concrete plants for this project and at peak demand, 300 cubes of concrete are crushed a day in the testing procedure. The quality of the BASF products and the high standards of our own teams have ensured that we have met our client’s expectations satisfactorily.
Concludes Heynes: “The building of this structure has been challenging and we are pleased to say we are part of building a facility that will serve Qatar and its people for many years.”