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Sat 6 Mar 2010 04:00 AM

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Recycled roads

Dr Olisanwendu Ogwuda discusses how infrastructure in the gulf region can be a valuable ‘virtual quarry' resource as structures near the end of their life span.

Recycled roads
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Roads are the main form of land transport in many countries and often carry more than 80% of passengers-km and over 50% of freight tonne-km in a country. Roads are important to the national economy and provide vital links to vast regional, urban, local and rural areas.Developed countries need to maintain their road networks for continued economic growth while developing countries are building their road networks to reach standards similar to developed countries. The developed economies pay more attention to the creation of a sustainable network either by new developments or by upgrading their existing network.

And, the emphasis in these markets is on new developments, by learning from the experience of developed economies, and making improvements to their networks. Developing countries will also need to give consideration to future maintenance needs. The nature of the market in any country in terms of the provision and maintenance of the road network is based mainly on price

Parts of the world have inadequate supplies of virgin aggregate and at the same time valuable construction rubble is being sent to land-fills or used as low-grade/low-value materials such as granular fills or sub-base material in roads. In other instances they are used as partial replacement materials within new high-energy products. A current barrier to a more effective and efficient use of construction rubble is concern over consistency of quality and predictability of performance. The concerns arise from current approaches in processing of construction rubble.

Processing is usually undertaken at waste transfer sites and the economics of the market are such that low-grade materials only are produced with minimum processing and little need for predictability of performance. Although specifications for use of recycled materials exist, the barrier of consistency and predictability of performance is significant.

However, specifiers need the confidence in high performance recycled materials. Herein lies the specifics of the barrier, which requires science and technology to underpin system development and performance prediction that is confirmed by actual performance in service, complemented by protocols to ensure consistency of material production and placement.

It should be noted that recycling is not an absolute solution to dwindling natural resources, but it can extend the life of non-renewable resources. The demand for materials for uses also needs to be put in context.

Even if all potential recyclable materials were recycled, the quantities are such that they would only meet a comparatively small proportion of the demand for construction materials. Non-renewable natural resources will therefore continue to have to meet the bulk of the demand for the foreseeable future. However, the decision-making process should be based on an overall appraisal of potential suitable materials, including recyclable materials.

The Gulf is well placed to embark on this journey of providing a more sustainable and ‘green' road infrastructure, where consistency and predictability of performance of the materials arising from virtual quarries can be evaluated. This journey should begin now to avoid the pitfalls of experiences in other parts of the world. Now is the time to take stock of existing and future building and civil engineering infrastructure.

We can evaluate the performance potential of these virtual quarries, which exist all around the Gulf, and how these may meet the future demand for road construction materials, at the same time ticking the ‘green' box of sustainability. This is an opportunity to lead with a form of construction that will cascade to what can be described as ‘fourth world countries' - developed countries of the future.

Ogwuda has been a senior teaching fellow and civil engineering course co-ordinator at Heriot-Watt University, Dubai Campus, since September 2009. He has over 15 years applied research and development experience, mainly from the UK, linking research and practice in environmental highway engineering. He has developed partnership opportunities that have provided commercially-focussed innovation, research and technology development in low energy and sustainable construction for roadways and footways. He is a member of the Institution of Highways and Transportation and the Institute of Asphalt Technology.

The opinions expressed in this column are of the author and not of the publisher.

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