Kooragang Island – Candac Thiess Joint Venture

Project Report

Stabilised Pavements of Australia (SPA) was contracted by the Candac Thiess Joint Venture on Kooragang Island near Newcastle to assist in extending the existing coal loading facilities. The Candac Thiess Joint Venture involved building an additional 1.4km to the reclaimer track, coal storage area and conveyor.

The work was to be completed within a strict time period and material for the extension consisted of sand dredged straight from the Hunter River, which was later stabilised with a mixture of cement and slag. All extensions were founded on a reclaimed sand base, which was formerly a swamp area. SPA was employed by the Candac Thiess Joint Venture to overcome the time restraints and the extremely poor quality of the soil to be stabilised.

Problems included cement spreaders sinking in the soft sand, and the extremely low water content in the mixed product. Such is the characteristic of sand that retention of water is near impossible and so to react with the cement/slag it was necessary to saturate the sand and to complete the work quickly, thereby achieving adequate compaction. Specially built 6 wheel drive Volvo cement spreaders were employed to overcome the poor traction encountered in the sand. These spreaders were used for the bulk of the project in conjunction with 2 CMI RS500 mixers.

Over the 6 month project, a series of berms were each built up over 13 lifts to a total of 4m in height. The stabilised sand involved an area of 1.1 million m² and a volume of 342,500 m³, using 31,000 tonnes of cement/slag. The coal loader extension will be required to support an additional 650,000 tonnes of stockpiled coal, and the coal reclaimer itself weighing 2,000 tonnes.

As well as stabilising the sand, a second project involved mixing bentonite with some 37,450 m² of sand to produce an impervious layer which could trap contaminated water running through the coal stockpile to then be treated. This process was required between the berms, thus maximising untreated water retention. Here, alternate bentonite and cement/slag layers were mixed, using a total of 1700 tonnes for each of the bentonite and the cement/slag mixes.

Although the construction site was a 24hr site, SPA generally mixed for an average of 10 hr days. Some of the best days achieved during these shifts included 440 tonnes of cement/slag used and 15,000 m² mixed. The finished berms now resemble a dense white sandstone, rather than what was only 6 months ago a cohesionless sand.