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Barrow Island Barge Berth Project, developed by Chevron Australia, is currently the world’s largest industrial project, with an estimated value of $60 billion. The project 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 supplied 2800 cubic metres of concrete for the wharf’s landing berth and quarantine truck-washing area.
Challenges and Solutions
Chevron’s stringent engineering standards, combined with a harsh environment characterised by exposure to erosive sea-conditions and daily ambient temperatures of over 45° C, have demanded a Best Team response from Karratha.
‘Firstly, our production and technical teams worked together to develop a S50 Marine mix that would satisfy the performance requirements specified by Chevron and their contracted engineers from Worley Parsons’, explained Walter Roemer, Karratha Plant Manager.
‘During the trial-mix process, the initial focus was durability and shrinkage. Waterproofing agents were added, as the six-metre tide variance at the wharf meant the concrete would be subject to extreme sea conditions, including large swells during cyclone periods. The agents created a non-soluble crystalline structure to permanently seal the concrete against the penetration of sea water’, he added.
Shrinkage agents ensured the mix achieved satisfactory microstrain results at 56 days, while super-plasticisers were added to achieve the 150 mm slump required for specified levels of pumpability and workability. After confirming the mix design, the Karratha team launched an exhaustive testing regime that continues today.
As part of the testing, mix samples are taken every 50 cubic metres; shrinkage testing is conducted every 150 cubic metres to help avoid structural cracking and joint-stability problems, and retarder dosage rates are carefully monitored for the duration of the project.
‘This is required due to the 40-minute travel time between the concrete plant and the site’, explained Walter.
As daily temperatures at the project and at Hanson’s Karratha plant rocket beyond 45°C, ensuring the concrete remains within required temperature levels is another challenge.
Major pours ranging from 50 to 300 cubic metres were conducted at night, starting at 1.00 am when temperatures drop below 35°C. Shade sails were installed 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 that all 2800 cubic metres of concrete supplied stayed within the specified acceptable temperature range, and avoided premature setting times’, said Walter.
Pre-pour meetings were also conducted periodically between Hanson, and Chevron representatives and the contracted Worley Parsons engineers. Plant meetings addressed all production issues before large pours.
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