Manufactured sands from hardrock quarries: Environmental solution or dilemma for southeast Queensland?

The closure of the Brisbane River to extractive dredging and the exhaustion or limitation of other sand sources have caused an industry shift to manufactured sand for concrete fine aggregates. Manufactured sand is generated in a purpose‐designed process; it is not recycled waste‐crusher dust. At present it is produced in 12 of the major hardrock quarries in southeast Queensland. To date companies have achieved only partial replacement of natural sands, to around 40% of the fine aggregate component in their concrete mixes. While improved technology and management will further reduce the amount of natural blend sand required, it is unlikely to be fully replaced in the foreseeable future. Although providing a solution to one problem, manufactured sand raises new environmental issues. The management of fine wastes is likely to become an important issue, as will the increased demand for natural fine sands to improve mix grading and workability. Diminishing supply from land‐based sources has resulted in increased applications for dredging of Moreton Bay, where enormous resources occur and low impact extraction may be possible. However, this prospect raises difficult environmental and land‐access issues for government decision makers.

Keywords:

• aggregates
• crushing
• environmental geology
• manufactured sands
• quarries
• Queensland