Wednesday, July 21, 2010
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The Barrow Island Barge Berth is located along the Burrup Peninsula in Dampier, thirty-five kilometres from Karratha.
Developed by Chevron Australia, it is currently the world’s largest industrial project with an estimated value of $60 billion.
It will develop the Greater Gorgon Area gas fields and includes the construction of a domestic gas plant and a 15 million tonne-per-annum Liquefield Natural Gas (LNG) plant on Barrow Island.
Hanson’s Karratha plant has supplied 2800m3 concrete for the wharf’s landing berth and quarantine truck-washing area.
The project has demanded an expert response from Karratha resulting from Chevron’s stringent engineering standards, daily ambient temperatures exceeding 45 degrees and the areas exposure to erosive sea-conditions.
“Firstly, our production and technical teams worked together to develop a S50 Marine mix which would satisfy the performance requirements specified by Chevron and their contracted engineers from Worley Parsons,” explains Walter Roemer, Karratha Plant Manager.
“During the trial-mix process, the initial focus was durability and shrinkage. Because a six-metre tide variance at the wharf meant the concrete would be subject to extreme sea conditions, especially with large swells during cyclone periods, water-proofing agents were added. The agents created a non-soluble crystalline structure to permanently seal the concrete against the penetration of sea water,” he adds.
Shrinkage agents ensured the mix achieved satisfactory microstrain results at 56 days, while super-plasticisers were added to achieve the 150mm slump required for specified levels of pumpability and workability.
After confirming the mix design, the Karratha team then launched an exhaustive testing regime.”
That included mix samples being taken every 50m3, shrinkage testing being conducted every 150m3 to help avoid structural cracking and joint-stability problems and retarder dosage rates being carefully monitored throughout the duration of the project.
“This was required particularly due to the forty-minute travel time between the concrete plant and the site,” adds Walter.
With daily temperatures at the project and Hanson’s Karratha plant beyond forty-five degrees, ensuring the concrete remained within required temperatures was another challenge.
Major pours ranging from 50m3 to 300m3 were conducted at night, starting at 1.00am when temperatures drop below thirty-five degrees.
Shade sails were also required over all aggregate bins at the plant and temperatures were further reduced by periodically spraying the aggregates with water to achieve an acceptable Surface Saturated State (SSS).
“Collectively, these measures ensured all 2800m3 supplied stayed within the specified acceptable temperature range, avoiding premature setting times,” says Walter.
Pre-pour meetings were also conducted periodically between Hanson with both Chevron representatives and contracted Worley Parsons engineers, as well as plant meetings to address all production issues before large pours.