Internationally, recycled roading materials are widely used.  Previously regarded as waste products, the new trend has demonstrated that certain recycled materials, particularly crushed concrete basecourse, are cost-effective and can outperform natural materials.

case study 3_photo2.jpgIn late 2003, Fulton Hogan sought the support of Christchurch City Council to help showcase the attributes of recycled materials in New Zealand.  The objective was to minimise environmental impacts and encourage sustainable outcomes in the roading industry.  A 300m-long stretch on Golf Links Road in Christchurch was chosen as the site for New Zealand’s first “green” road, using 100% recycled materials.

Golf Links Road is a busy section of road behind a
shopping mall, with high numbers of heavy service vehicles.  Using recycled materials on this road has provided a true test of their constructability and durability.

After extensive research, crushed concrete and recycled asphalt were chosen as the most appropriate materials to use in construction of the road – both readily available and commonly used in other parts of the world.  The road was completed in June 2005 and is made up of 3000m3 of concrete, including a sub-base of AP65 crushed concrete, and a base of AP40 crushed concrete.  The top layer was made of recycled asphalt, using material from the millings of other job sites that was reheated and constituted into 15mm-thick asphalt.

One of the major challenges the Fulton Hogan team faced was ensuring that the concrete was substantially free from contamination by other building products, such as plastic, brick and timber.

The Golf Links Road project offered significant environmental and economic benefits.  It proved recycling can deliver a huge reduction in the dumping of used concrete and asphalt, as the materials can be used repeatedly as roads are replaced.  Significant cost savings can also be achieved.  In addition, the use of recycled materials saves on non-renewable natural resources, such as quarry aggregate and petroleum-based bitumen.

Recycled materials also offer performance benefits, as the residual cement content of the crushed concrete means it may have higher strength and can perform better than natural aggregate. In addition, the extra water required for compacting crushed concrete means it is well suited to winter construction, when the weather is not suitable for other materials.

When comparing the cost of materials used in isolation using recycled materials for the project had a small additional cost compared with the cost of using conventional materials.  However, this does not take into account a whole of life consideration for the disposal of the materials involved, which would significantly increase the overall cost of using conventional materials.

The Golf Links Road project shows that the use of recycled crushed concrete and reclaimed asphalt product offer a high-strength solution, together with the additional benefits of cost reduction, higher performance, and suitability for winter construction.